RU2817767C1 - Method of obtaining image of geographic region and imaging system - Google Patents

Abstract

FIELD: satellite communication.

SUBSTANCE: said technical result is achieved due to the fact that the illumination satellite in the first orbit, beam signals (e.g., communication signals carrying modulated data to user terminals) from an antenna array to different beam coverage areas in accordance with the beam forming matrix; each of the collection satellites in the second orbit receives beam signal reflections; reflected signals received on collection satellites, may be processed in accordance with beam signals and beam forming matrix used to transmit beam signals to obtain an image of a geographic area. In some cases, the collection satellites can relay the received signals for processing by the illumination satellite.

EFFECT: creation of an improved method and system for obtaining an image of a geographic region using a multistatic synthetic aperture radar using data collection in a low earth orbit.

18 cl, 14 dwg

Description

State of the art

The following applies generally to multi-orbit satellite systems and, more specifically, to multistatic synthetic aperture radars employing low-Earth orbit data acquisition. Synthetic aperture radar can be used to improve spatial resolution by combining signals associated with multiple radar illuminator or receiver locations. Uses of synthetic aperture radar include scientific or environmental monitoring, and surveillance of the movement of objects of interest to assets or military intelligence.

The essence of the invention

The described methods relate to improved methods, systems, devices and apparatus supporting multi-static synthetic aperture radar using data acquisition in low Earth orbit. In some examples, an illumination satellite may be in a first orbit and multiple acquisition satellites may be in a second orbit. The lighting satellite can transmit beamforming lighting signals, such as beamforming communication signals, to different beamforming coverage areas. Each of the collection satellites can receive beamforming reflections of illumination signals. The reflected signals received at the acquisition satellites may be processed in conjunction with a beamforming matrix used to transmit beamforming lighting signals to produce an image of a geographic area. In some cases, beamforming lighting signals may carry communication signals (eg, modulated data) intended for user terminals in coverage areas. In some cases, collection satellites may relay received signals for processing by an illumination satellite.

Brief description of graphic materials

In fig. 1A shows a diagram of a satellite system that supports a multistatic synthetic aperture radar employing low-Earth orbit data acquisition, in accordance with the examples disclosed herein.

In fig. 1B illustrates a satellite antenna assembly that supports a multistatic synthetic aperture radar, in accordance with the examples disclosed herein.

In fig. 1C illustrates a feed array assembly of an antenna assembly that supports a multistatic synthetic aperture radar, in accordance with the examples disclosed herein.

In fig. 2A-2B illustrate examples of antenna performance for an antenna assembly having a feed array assembly that supports a multistatic synthetic aperture radar, in accordance with the examples disclosed herein.

In fig. 3A and 3B illustrate an example of beamforming for generating focused beam coverage areas over a local antenna pattern coverage area in accordance with the examples disclosed herein.

In fig. 4 illustrates an example of a reception processing system that supports a multistatic synthetic aperture radar, in accordance with the examples disclosed herein.

In fig. 5 illustrates an example of a composite beam coverage pattern that supports a multistatic synthetic aperture radar, in accordance with the examples disclosed herein.

In fig. 6 is a diagram of a system comprising an apparatus that supports multistatic synthetic aperture radar techniques in accordance with the examples disclosed herein.

In fig. 7 illustrates a process flow that supports multistatic synthetic aperture radar techniques in accordance with the examples disclosed herein.

In fig. 8 shows a diagram of a multi-static SAR processor that supports multi-static synthetic aperture radar techniques using low-Earth orbit data acquisition, in accordance with the examples disclosed herein.

In fig. 9 is a diagram of a system comprising an apparatus that supports multistatic synthetic aperture radar techniques in accordance with examples disclosed herein.

In fig. 10 is a block diagram illustrating a method that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein.

Detailed Description of the Invention

A system in accordance with the methods described herein can support various examples of multistatic synthetic aperture radar using low-Earth orbit data acquisition. In some cases, a communications satellite can be used as an illumination source for a multistatic synthetic aperture radar. A communications satellite may, for example, be in geostationary orbit and may operate in a multiple spot beam mode, transmitting or receiving in accordance with a number of relatively narrow spot beams aimed at different regions of the earth. A satellite system containing an illumination satellite may use on-satellite beamforming, ground-based beamforming, or end-to-end beamforming.

The satellite system may contain a number of collection satellites, which may be in a different orbit (eg, low Earth orbit) than the illumination satellite. Illumination signals transmitted by an illumination satellite can be reflected from the earth's surface, including objects or other elements, and received by collection satellites in a multistatic configuration. Collection satellites may transmit information (eg, digital samples) from the received signals to one or more ground stations (eg, directly or through one or more other satellites, such as a lighting satellite). The aperture for displaying the received signals may be determined by the number of collection satellites receiving signals reflected in multiple directions, including the spatial relationship between the collection satellites and the relative movement of the collection satellites relative to the illuminated region and the position of the illumination satellite. Multistatic data from multiple sampled signals (eg, representing multiple beam signals) from each of multiple collection satellites representing reflected signals during the same time period can be used to determine geospatial aperture information associated with the size of the collection satellite positions. The multistatic aperture can be combined with a synthetic aperture for each of the illumination sources (for example, when the collection satellites intersect their orbital paths). Images for a region (eg, including one or more beam coverage areas) can be obtained from reflected signals and beam information (eg, beam coefficients, beam signals).

Various examples of multistatic synthetic aperture radar techniques using low-Earth orbit data acquisition are proposed herein, and such examples are not intended to limit the scope, applicability, or configuration of the examples in accordance with the principles described herein. Rather, in the following description, those skilled in the art will be provided with descriptions that enable embodiments of the principles described herein to be implemented. Various changes may be made to the function and arrangement of elements.

Thus, in various embodiments of the invention in accordance with the examples disclosed herein, various procedures or components may be omitted, replaced, or added as necessary. For example, it should be understood that the methods may be performed in an order different from that described, and that various steps may be added, omitted, or combined. Additionally, aspects and elements described with respect to certain examples may be combined in various other examples. It should also be understood that the following systems, methods, devices and software may individually or collectively constitute components of a larger system, and other procedures may take precedence over or otherwise alter their use.

In fig. 1 shows a diagram of a satellite system 100 that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. The satellite system 100 may utilize a number of network architectures, including a space segment 101 and a ground segment 102. The space segment 101 may include one or more satellites 120. The ground segment 102 may include one or more access node terminals 130 (e.g., gateway terminals , ground stations), as well as other central processing centers or devices such as network operations centers (NOCs) or satellite and gateway terminal command centers (not shown). In some examples, ground segment 102 may also include user terminals 150 that are provided with communication service via satellite 120.

In various examples, satellite 120 may be configured to support wireless communications between one or more access node terminals 130 and/or various user terminals 150 located within the service coverage area, which in some examples may be the primary mission or purpose of satellite 120. In some In examples, satellite 120 may be deployed in a geostationary orbit (GEO) such that its orbital position with respect to ground devices is relatively stationary or stationary within an operational tolerance or other orbital window (eg, within an orbital position). In other examples, satellite 120 may operate in any suitable orbit (eg, low Earth orbit (LEO), medium Earth orbit (MEO), etc.).

Satellite 120 may use an antenna assembly 121, such as a phased array antenna assembly (e.g., a direct radiating array (DRA)), a phased array feed reflector (PAFR) antenna, or any other mechanism known in the art to receive or transmit signals (for example, communication or broadcasting services or data collection services). In support of a communications service, satellite 120 may receive forward uplink signals 175 from access node terminals 130 and transmit forward downlink signals 170 to one or more user terminals 150. Satellite 120 may also receive reverse uplink signals 171 from one or more user terminals 150 and transmit reverse downlink signals 176 to one or more access node terminals 130. Satellite 120 may use a variety of physical layer modulation and transmission coding techniques to transmit signals between access node terminals 130 or user terminals 150 (eg, adaptive coding and modulation (ACM)).

Antenna assembly 121 may support communication or other signal reception via one or more focused beamforming beams 125, which may otherwise be referred to as service beams, satellite beams, or any other suitable terminology. The signals may pass through the antenna assembly 121 according to the spatial electromagnetic radiation pattern of the spot beams 125. In support of a communications service, the spot beam 125 may use a single carrier, such as a single frequency or a continuous range of frequencies, which may also be associated with a single polarization. In some examples, the spot beam 125 may be referred to as a user spot beam or user beam. For example, user spot beam 125 may be configured to support one or more forward downlink signals 170 and/or one or more reverse uplink signals 171 between satellite 120 and user terminals 150. Communication between satellite 120 and access node terminals 130 may be accomplished through access node spot beams (not shown), which may also be called gateway beams.

Spot beam 125 may support communication service between target devices (eg, user terminals 150 and/or access node terminals 130) or other signal reception within spot beam coverage area 126. The focus beam coverage area 126 may be defined by the area of the electromagnetic radiation pattern of the corresponding focus beam 125 projected onto the ground or some other reference surface having a signal strength, signal-to-noise ratio (SNR), or signal-to-interference-plus-noise ratio (SINR ) of the focused beam 125 above a threshold value (eg, an absolute threshold value or a threshold value relative to the center of the beam). The spot beam coverage area 126 may cover any suitable service area (eg, circular, elliptical, hexagonal, local, regional, national) and can support communication service with any number of target devices located within the spot beam coverage area 126. In various examples, target devices, such as airborne or subsea target devices, may be located within the focus beam 125, but are not located on the support surface of the focus beam coverage area 126 (e.g., support surface 160, which may be an earth surface, a land surface , the surface of a body of water such as a lake or ocean, or a supporting surface at an elevation or height).

Beamforming for a communication channel can be accomplished by adjusting the signal phase (or time delay) and sometimes the signal amplitude of signals transmitted and/or received by multiple feed elements of one or more antenna assemblies 121 with overlapping local feed element radiation patterns. In some examples, some or all of the feed elements may be arranged in an array of constituent receive and/or transmit feed elements that interact with each other to provide various examples of on-board beamforming (OBBF), ground-based beamforming (GBBF), end-to-end beamforming or other types of beamforming.

The satellite 120 may support multiple beamforming spot beams 125 covering respective spot beam coverage areas 126, each of which may or may not overlap with adjacent spot beam coverage areas 126. For example, satellite 120 may support a service coverage area (eg, regional coverage area, national coverage area, hemispherical coverage area) formed by a combination of any number (eg, tens, hundreds, thousands) of spot beam coverage areas 126. Satellite 120 may support a communications service over one or more frequency bands and any number of subbands thereof. For example, satellite 120 may support Ku-, K-, or Ka-band, C-band, X-band, S-band, L-band, and International Telecommunications Union (ITU) V-band operation, and the like.

In some examples, a service coverage area may be defined as a coverage area from and/or to which either a terrestrial transmission source or a terrestrial receiver may be engaged in a communications service (e.g., transmit and/or receive signals associated therewith) via satellite 120 and may be defined by a plurality of focused beam coverage areas 126. In some systems, the service coverage area for each communication channel (eg, forward uplink coverage, forward downlink coverage, reverse uplink coverage, and/or reverse downlink coverage) may be different. While the service coverage area may only be active when satellite 120 is engaged in service (e.g., in a service orbit), satellite 120 may have (e.g., be designed or configured to have) its own antenna pattern based on the physical components of the antenna assembly 121 and their relative positions. The intrinsic radiation pattern of the satellite antenna 120 may refer to the distribution of energy relative to the satellite antenna node 121 (eg, the energy transmitted by and/or received by the antenna node 121).

In some service coverage areas, adjacent spot beam coverage areas 126 may have some degree of overlap. In some examples, a multi-color diagram (eg, a two-, three-, or four-color reuse diagram) may be used, with “color” referring to a combination of orthogonal communication resources (eg, frequency resources, polarization, etc.). In an example four-color diagram, overlapping focus beam coverage zones 126 may be assigned one of four colors, and each color may be assigned a unique combination of frequencies (e.g., frequency range or ranges, one or more channels) and/or signal polarization (e.g., right circular polarization (RHCP), left-handed circular polarization (LHCP), etc.) or other orthogonal resources. Assigning different colors to respective spot beam coverage areas 126 that have overlapping regions can reduce or eliminate interference between spot beams 125 associated with those overlapping spot beam coverage areas 126 (e.g., by scheduling transmissions that correspond to the respective spot beams according to the respective colors, by filtering transmissions that correspond to the corresponding focused beams according to the corresponding colors). Accordingly, these combinations of frequency and antenna polarization can be reused in a repeating non-overlapping "four-color" reuse pattern. In some examples, the communication service may be provided using more or fewer colors. In an additional or alternative embodiment, time sharing among the focused beams 125 and/or other interference suppression techniques may be used. For example, spot beams 125 may simultaneously use the same resources (same polarization and frequency range) with interference suppressed using suppression techniques such as ACM, interference cancellation, space-time coding, and the like.

In some examples, satellite 120 may be configured as a curved tube satellite. In a curved tube configuration, satellite 120 may perform frequency and polarization conversion on received carrier signals before retransmitting the signals to their destination. In some examples, satellite 120 may support a raw curved tube architecture with phased array antennas used to create relatively small spot beams 125 (eg, via GBBF). Satellite 120 may support K common paths, each of which may be allocated as a forward path or a return path at any given time. Relatively large reflectors can be illuminated by a phased array of antenna feed elements, allowing for the creation of different focused beam patterns 125 within the constraints of reflector size and the number and placement of antenna feed elements. Phased array feed reflectors can be used to receive uplink signals, transmit downlink signals, or both.

Satellite 120 may operate in a multiple spot beam mode, transmitting or receiving in accordance with a number of relatively narrow spot beams 125 directed to different regions of the earth. This may provide separation of user terminals 150 into different narrow spot beams 125 or otherwise support spatial separation of transmitted or received signals. In some examples, beamforming networks (BFNs) associated with receive (Rx) or transmit (Tx) phased arrays may be dynamic, allowing the locations of Tx spot beams 125 (e.g., downlink spot beams 125) and Rx spot beams 125 to move. (eg, uplink spot beams 125).

User terminals 150 may include various devices configured to transmit signals via satellite 120, which may include fixed terminals (e.g., land-based fixed terminals) or mobile terminals such as terminals on boats, aircraft, land vehicles and so on. User terminal 150 may transmit data and information via satellite 120, which may include communication through access node terminal 130 with a destination device, such as network device 141, or some other device or distributed server associated with network 140. User terminal 150 150 can transmit signals in accordance with various modulation and transmission coding techniques at the physical layer, including, for example, those defined by the following standards: Digital Video Broadcasting - Satellite - Second Generation (DVB-S2), Worldwide Compatibility for Microwave Access (WiMAX), a cellular communications protocol such as Long Term Evolution (LTE) or fifth generation (5G) protocol, or Data Over Cable Interface Specification (DOCSIS) standards.

Access node terminal 130 may transmit forward uplink signals 175 to satellite 120 and receive reverse downlink signals 176 from it. The access node terminals 130 may also be referred to as ground stations, gateways, gateway terminals, or hubs. The access node terminal antenna system 131 may be bifacial and may be designed with sufficient transmit power and receive sensitivity to reliably communicate with satellite 120. In some examples, access node terminals 130 may include a parabolic reflector with high directivity in the direction of satellite 120 and low directivity in others. directions. The access node terminals 130 may comprise a variety of alternative configurations and include performance characteristics such as high isolation between orthogonal polarizations, high efficiency across operating frequency bands, low noise, and the like.

In support of the communications service, access node terminal 130 may schedule traffic to user terminals 150. Alternatively, such scheduling may occur in other parts of the satellite system 100 (for example, in one or more network devices 141, which may include a NOC and/or gateway command center). Although in FIG. 1 shows a single access node terminal 130, examples in accordance with the present invention may be implemented in communication systems having multiple access node terminals 130, each of which may be connected to others and/or to one or more networks 140 or network devices 141.

Satellite 120 may communicate with access node terminal 130 by transmitting reverse downlink signals 176 and/or receiving forward uplink signals 175 via one or more access node spot beams. Each of the access node spot beams may be associated with a separate return channel of the antenna node 121 (eg, GBBF) or each access node spot beam may be associated with multiple channels of the antenna node 121 (eg, OBBF or end-to-end beamforming).

Access node terminal 130 may provide an interface between network 140 and satellite 120 and, in some examples, may be configured to receive data and information sent between network 140 and one or more user terminals 150. Access node terminal 130 may format data and information for delivery to respective user terminals 150. Likewise, access node terminal 130 may be configured to receive signals from satellite 120 (eg, originating from one or more user terminals 150 and directed to a destination accessible via network 140). Access node terminal 130 may also format received signals for transmission over network 140.

The network(s) 140 may be any type of network and may include, for example, the Internet, an Internet Protocol (IP) network, an intranet, a wide area network (WAN), a metropolitan area network (MAN). ), local area network (LAN), virtual private network (VPN), virtual LAN (VLAN), fiber optic network, hybrid fiber-coaxial network, cable network, public switched telephone network (PSTN), public switched data network (PSDN ), a public land mobile network and/or any other type of network supporting communications between devices as described in this document. Network(s) 140 may include both wired and wireless connections, as well as optical links. Network(s) 140 may connect access node terminal 130 to other access node terminals, which may be in communication with the same satellite 120 or with other satellites 120 or other vehicles.

One or more network devices 141 may be associated with the access node terminals 130 and may control aspects of the satellite system 100. In various examples, the network device 141 may be co-located or otherwise located adjacent to the access node terminals 130 or may be a remote installation that communicates with access node terminals 130 and/or network(s) 140 via wired and/or wireless communication channel(s). Network devices 141 may include a beamforming processor 135 that may perform aspects related to generating coefficients for beamforming (eg, for OBBF, GBBF, end-to-end beamforming) and applying the coefficients (eg, for GBBF or end-to-end beamforming). For example, beamforming processor 135 may create coefficients to be applied to beam signals, and may apply coefficients to beam signals to obtain access node signals to be transmitted from one or more access node terminals 130, and may provide access node signals to one or more terminals. 130 access nodes for transmission.

Satellite 120 can be used as an illumination source for a multistatic synthetic aperture radar. Satellite system 100 may also include one or more collection satellites 122 that are in a different orbit than satellite 120. For example, lighting satellite 120 may be a GEO satellite, while collection satellites 122 may be LEO or MEO satellites. . Lighting signals transmitted by satellite 120 (eg, forward downlink signals 170) may be reflected from surface 160 or objects 155 and received by collection satellites 122 in a multistatic configuration. That is, the same illumination signal (e.g., forward downlink signals 170) may be reflected and received at different angles by collection satellites at different orbital positions that have simultaneous fields of view that include one or more focused beam coverage areas 126 . Thus, at each point in space and time, each of the collection satellites 122 can sample the same signal reflected in different directions. In addition, the acquisition satellites 122 may sample the signal over multiple time points. For example, as acquisition satellites 122 traverse their orbital path, they may produce multiple samples of signals (eg, forward downlink signals 170) reflected from a given spot beam coverage area 126. Thus, the aperture for displaying received signals may be determined by the number of collection satellites 122 sampling the signal reflected in multiple directions, including the spatial relationship between collection satellites 122 and the relative movement of collection satellites 122 relative to the illuminated region (e.g., a given spot beam coverage area 126 ) and satellite 120 lighting.

In some cases, collection satellites 122 may transmit information (eg, digital samples) from the received signals to one or more ground stations. For example, collection satellites 122 may transmit information via satellite 120 to one or more access node terminals 130. In some cases, the collection satellites 122 may transmit information over a communications link 172 associated with a communications service provided by the satellite 120. In some cases, the signals transmitted by the collection satellites 122 over a communications link 172 may be used by the satellite 120 or access node terminals 130 to determine the position of the satellites. 122 fees. For example, communication channel 172 may be synchronized with satellite 120 or include timestamp information, and the position of acquisition satellites 122 may be determined based on the timing information. In some cases, the position may be determined based on the timing information and the known orbit of the collection satellites 122.

In some examples, satellite system 100 may include more than one satellite for lighting. For example, satellite system 100 may include multiple GEO satellites, each of which transmits spot beams 125, with some spot beams from each of the multiple GEO satellites at least partially overlapping. Multiple GEO satellites covering the same area can provide additional precision through temporal and spatial diversity. For example, a first illumination signal may be transmitted from a first GEO satellite and collected by each of multiple LEO acquisition satellites, and a second illumination signal may be transmitted from a second GEO satellite and collected by each of several LEO acquisition satellites. Thus, cross-course interferometry can be used to improve ranging and azimuth accuracy through the long baseline triangulation provided by multiple illumination and acquisition satellites. A large effective aperture can provide higher accuracy than a synthetic aperture and can also be combined with a synthetic aperture for each of the illumination sources (for example, when collection satellites cross their orbital paths). Multiple illumination sources can also increase the effective cross-section of the target being diffused by simultaneously receiving multiple signals from different angles.

Using the 120 GEO satellite for lighting may provide other benefits. For example, high power (e.g., kilowatts or more) can be used to transmit synthetic aperture radar illumination signals. This may limit the LEO satellite's duty cycle to transmit to short bursts or fractions of its orbital period. In contrast, GEO communications satellites are generally much larger and designed to operate continuously. Thus, LEO collection satellites 122 that do not transmit lighting signals may be simpler and more economical to manufacture.

In some cases, an illumination satellite (eg, GEO satellite 120) may transmit a reference signal (eg, a beacon signal) used to determine the frequency, phase, or timing of signals received by the collection satellites 122. For example, GEO satellite 120 may transmit a beacon signal 180 across a wide area, including a service area having beam coverage areas 126 and collection satellites 122 . In some cases, collection satellites 122 may use the beacon signal 180 to determine the frequency, phase, or arrival time of the reflected beam signals 128 . In an additional or alternative embodiment, the collection satellites 122 may receive the forward downlink signals 170 (eg, just before the reflection) and use the forward downlink signals 170 as a reference to determine the frequency, phase, or arrival time of the reflected beam signals 128.

In some cases, beam signals 170 may be modulated to include timing and phase reference information. For example, beam signals 170 may include timestamps in each of several synchronization periods. In an additional or alternative embodiment, the beam signals 170 may include phase reference information, such as phase reference symbols, which can be used by collection satellites 122 to match the phase reference information in the beacon signal to provide phase information in the reflected signals.

In some cases, collection satellites 122 may sample the reflected signals and send the sampled signals to the multistatic SAR processor 145 for processing. Collection satellites 122 may transmit sampled signals via GEO satellite 120 to one or more access node terminals 130, which may transmit sampled signals to network devices 141. For example, collection satellite 122-a may transmit sampled signals on a reverse uplink channel 172-a. communication, and the acquisition satellite 122-b may transmit the sampled signals on the reverse uplink of communication channel 172-b. In some cases, satellite 120 may be an end-to-end relay such that each of multiple access node terminals 130 may receive a composite signal of sampled signals via respective subsets of the GEO satellite 120's transmit/receive paths. Beamforming processor 135 may combine composite signals received at multiple access node terminals 130 (eg, according to an inverse beamforming matrix) to obtain sampled signals from the collection satellite. Beamforming processor 135 may send the sampled signals to multistatic SAR processor 145 for processing.

Multi-static SAR processor 145 may receive sampled signals from each of one or more collection satellites 122 during a given period of time and use the built-in timing and phase information (for example, in combination with phase information from the collection satellite determined based on the beacon signal) and known beam signal information to determine geospatial information for each reflected beam signal. Multi-static SAR processor 145 may synthesize multi-static data from multiple sampled signals (e.g., representing multiple beam signals) from each of multiple collection satellites representing return signals during the same time period to determine geospatial aperture information associated with position sizes collection satellites. In some examples, multistatic SAR processor 145 may combine information from multiple acquisition satellites, multiple beam signals, and across time periods to produce multistatic and synthetic aperture for improved resolution and accuracy. Although shown as separate, multistatic SAR processor 145 may be included or co-located with network devices 141.

In fig. 2A illustrates an antenna assembly 121 of a satellite 120 that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. As shown in FIG. 2A, antenna assembly 121 may include a feed array assembly 127 and a reflector 122 shaped to have a focal region 123 where electromagnetic signals (eg, incoming electromagnetic signals 280) are concentrated when received from a remote source. Likewise, a signal emitted by the feed array node 127 located at the focal region 123 will be reflected by the reflector 122 into an outgoing plane wave (eg, outgoing electromagnetic signals 280). The feed array assembly 127 and the reflector 122 may be coupled to a proprietary antenna pattern formed by a combination of the distinct feed element patterns for each of the plurality of feed elements 128 of the feed array assembly 127.

Satellite 120 may operate according to antenna node 121's own antenna pattern when satellite 120 is in a servicing orbit, as described herein. The antenna's own radiation pattern may be based at least in part on the radiation pattern of the feed elements 128 of the feed array assembly 127, the relative position (e.g., focal offset distance 129 or lack thereof in the focused position) of the feed array assembly 127 relative to the reflector 122, etc. d. The antenna's own radiation pattern can be related to the coverage area of the antenna's own radiation pattern. The antenna nodes 121 described herein may be configured to support a specific service coverage area with the antenna node 121's own antenna pattern coverage area, and various design characteristics may be determined computationally (e.g., by analysis or simulation) and/or measured experimentally (e.g. in the antenna test range or in actual use).

As shown in FIG. 2A, a feed array unit 127 of the antenna assembly 121 is located between the reflector 122 and a focal region 123 of the reflector 122. Specifically, the feed array unit 127 is located at a focal offset distance 129 from the focal area 123. Accordingly, the feed array unit 127 of the antenna assembly 121 may be located in a defocused position relative to the reflector 122. Although in FIG. 2A is illustrated as a forward bias feed array assembly 127, a front feed array assembly 127 may be used, as well as other types of configurations including the use of a secondary reflector (e.g., Cassegrain antenna, etc.), or a configuration without reflector 122 (e.g., DRA ).

In fig. 2B illustrates a feed array assembly 127 of an antenna assembly 121 that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. As shown in FIG. 2B, feed array assembly 127 may have multiple feed elements 128 for transmitting signals (eg, signals associated with a communications service, signals associated with the configuration or control of satellite 120, received data acquisition signals, or sensor locations).

As used herein, feed element 128 may refer to a receiving antenna element, a transmitting antenna element, or an antenna element configured to support both transmission and reception (eg, a transceiver element). The receiving antenna element may include a physical transducer (eg, a radio frequency (RF) transducer) that converts the electromagnetic signal into an electrical signal, and the transmitting antenna element may include a physical transducer that emits an electromagnetic signal when excited by the electrical signal. In some cases, the same physical converter can be used for transmission and reception.

Each of the feed elements 128 may include, for example, a feed horn, a polarization converter (e.g., a polarized baffle horn that can function as two combined elements with different polarizations), a multi-port, multi-band feed horn (e.g., a dual-band 20 GHz/30 GHz dual polarized (LHCP/RHCP), slot resonator, inverted F, slot waveguide, Vivaldi device, helix, loop, patch antenna, or any other antenna element configuration or combination of interconnected subelements. Each of the feed elements 128 may also include. an RF signal converter or otherwise coupled thereto, a low noise amplifier (LNA), or a power amplifier (PA), and may also be coupled to repeaters in satellite 120 that may perform other signal processing such as frequency conversion, beamforming processing and so on.

The reflector 122 may be configured to reflect signals between the illumination array node 127 and one or more target devices (eg, user terminals 150, access node terminals 130) or objects (eg, terrain, vehicles, buildings, airborne objects). Each feed element 128 of the feed array assembly 127 may be associated with a corresponding feed pattern of its own, which may be associated with a projected coverage area of the feed array's own pattern (e.g., projected onto a ground surface, plane, or volume after reflection from reflector 122). The set of coverage areas of the own radiation pattern of the feeding elements for an antenna with several feeds can be called the antenna’s own radiation pattern. The irradiation array assembly 127 may contain any number of irradiation elements 128 (e.g., tens, hundreds, thousands, etc.), which may be in any suitable arrangement (e.g., a linear array, an arcuate array, a flat array, a honeycomb array, polyhedral lattice, spherical lattice, ellipsoidal lattice or combinations thereof). Irradiating elements 128 may have ports or apertures of various shapes, such as circular, elliptical, square, rectangular, hexagonal, and others.

In fig. 3A, 3B, 4A, and 4B illustrate examples of antenna performance for an antenna assembly 121-a having a feed array assembly 127-a that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. document. Antenna assembly 121-a may operate under conditions in which received transmissions from a given location are distributed over a plurality of feed elements 128-a, or the transmitted power from feed element 128-a is distributed over a relatively large area, or both.

In fig. 3A shows a diagram 201 of the intrinsic radiation pattern 210-a of the feed elements associated with the feed elements 128-a of the feed array assembly 127-a. In particular, diagram 201 illustrates the intrinsic radiation patterns 210-a-1, 210-a-2 and 210-a-3 associated with the feed elements 128-a-1, 128-a-2 and 128-a- 3 respectively. The feed element's own radiation patterns 210-a may represent the spatial radiation pattern associated with each of the respective feed elements 128. For example, when the feed element 128-a-2 is in transmit mode, the transmitted electromagnetic signals may be reflected from the reflector 122-a and propagate in a predominantly conical intrinsic radiation pattern 210-a-2 of the irradiating elements (although other shapes are possible depending on the characteristics of the irradiating element 128 and/or reflector 122). Although three feed element signatures 210-a are shown for antenna assembly 121-a, each feed element 128 of antenna assembly 121 is associated with a corresponding feed element pattern 210. A set of intrinsic radiation patterns 210-a of the feed elements associated with antenna assembly 121-a (for example, intrinsic radiation patterns 210-a-1, 210-a-2, 210-a-2 of the feed elements and other intrinsic radiation patterns 210-a feed elements that are not illustrated) may be referred to as the antenna's own radiation pattern 220-a.

Each of the feed elements 128-a may also be associated with a self-pattern coverage area 211-a (e.g., self-pattern coverage areas 211-a-1, 211-a-2, and 211-a-3, associated with the irradiating elements 128-a-1, 128-a-2 and 128-a-3, respectively), representing the projection of the irradiating elements' own radiation patterns 210-a onto a supporting surface (for example, a ground or water surface, a supporting surface on an elevated surface, or any other reference plane or surface). The feed element's own beam coverage area 211 may be an area in which various devices (e.g., access node terminals 130 and/or user terminals 150) can receive signals transmitted by the corresponding feed element 128. In an additional or alternative embodiment, the feed element's own beam coverage area 211 The radiation pattern of the feed elements may be an area in which transmissions from various devices can be received by the corresponding feed element 128. For example, a device located in the zone of interest 230-a located within the zones 211-a-1, 211-a-2 and 211-a-3 covering the feed elements' own radiation pattern, can receive signals transmitted by feed elements 128-a-1, 128-a-2 and 128-a-3, and may have transmissions received by feed elements 128-a- 1, 128-a-2 and 128-3-a. A combination of self-pattern coverage zones 211-a associated with antenna assembly 121-a (e.g., self-pattern coverage zones 211-a-1, 211-a-2, 211-a-2 and other beam-pattern coverage zones 211 -a self-pattern coverage of feed elements that are not illustrated) may be referred to as antenna self-pattern coverage area 221-a.

The irradiation array assembly 127-a may operate in a defocused position relative to the reflector 122-a such that the irradiation elements' own radiation patterns 210-a, and thus the irradiation elements' own radiation pattern coverage areas 211-a, substantially overlap. Therefore, each position in the antenna's own radiation pattern coverage area 221-a may be associated with a plurality of feed elements 128 such that a plurality of feed elements 128 may be used for transmissions to or receptions from a point of interest. 201 is not to scale and that each of the coverage areas 211 of the irradiating element's own radiation pattern is typically much larger than the reflector 122-a.

In fig. 3B is a diagram 202 illustrating signal reception by antenna assembly 121-a for transmissions 240-a from point of interest 230-a. Transmissions 240-a from point of interest 230-a may illuminate all of reflector 122-a or some portion of reflector 122-a and then be focused and directed toward irradiating array node 127-a according to the shape of reflector 122-a and the transmission's incidence angle. 240 on reflector 122-a. The feed array assembly 127-a may be operated in a defocused position relative to the reflector 122-a such that transmission 240-a may be focused on a plurality of feed elements 128 (e.g., feed elements 128-a-1, 128-a-2 and 128-a-3 associated with the coverage areas 211-a-1, 211-a-2 and 211-a-3 of the own radiation pattern of the irradiating elements, each of which contains a point of interest 230-b).

In fig. 4A shows a diagram 203 of the self-pattern gain profiles 250a of the feed elements associated with the three feed elements 128a of the feed array assembly 127a, with respect to angles measured from the zero offset angle 235a. For example, feed element self-pattern gain profiles 250-a-1, 250-a-2, and 250-a-3 may be associated with feed elements 128-a-1, 128-a-2, and 128-a-3, respectively. and therefore can represent the gain profiles of the feed elements' own radiation patterns 210-a-1, 210-a-2 and 210-a-3. As shown in diagram 203, the gain of each gain profile 250 of the feed elements' own radiation pattern may decay at angles offset in any direction from the peak gain. In diagram 203, beam contour layer 255-a may represent a required gain level (eg, to provide a required information rate) to support a communications service or other receive or transmit service via antenna node 121-a, which may therefore be used to determine boundaries of the corresponding self-pattern coverage zones 211-a (eg, self-pattern coverage zones 211-a-1, 211-a-2 and 211-a-3). The beam contour level 255a may represent, for example, -1 dB, -2 dB, or -3 dB attenuation from peak gain, or may be determined by absolute signal power, SNR level, or SINR level. Although three feed element self-gain profiles 250a are shown, other feed element self-gain profiles 250a may be associated with other feed elements 128a.

As shown in diagram 203, each of the self-beam gain profiles 250a may intersect with another self-beam gain profile 250a for a significant portion of the gain profile above the beam contour level 255a. Accordingly, diagram 203 illustrates the arrangement of feed element self-pattern gain profiles 250, where multiple feed elements 128 of the feed array assembly 127 can support signal transmission at a particular angle (eg, in a particular direction of the antenna's own radiation pattern 220-a). In some examples, this condition may be referred to as the presence of feed elements 128 of feed array node 127 or coverage areas 211 of the feed elements' own radiation pattern having a high degree of overlap.

In fig. 4B is a diagram 204 illustrating a two-dimensional array of idealized feed element self-pattern coverage zones 211 of multiple feed elements 128 of a feed array node 127-a (e.g., including feed elements 128-a-1, 128-a-2, and 128-a-3 ). Coverage zones 211 of the irradiating elements' own radiation pattern may be illustrated with respect to a reference surface (e.g., a plane at a distance from a communications satellite, a plane at some distance from the ground, a spherical surface at some height, the earth's surface, etc.) and may additionally include a volume adjacent to the support surface (eg, a substantially conical volume between the support surface and the communications satellite, a volume below the support surface, etc.). Several feed element self-pattern coverage zones 211-a can jointly form an antenna self-pattern coverage zone 221-a. Although eight self-pattern coverage zones 211a are illustrated, the feed array assembly 127 may have any number of feed elements 128 (e.g., less than eight or more than eight), each of which is associated with a self-pattern coverage zone 211.

The boundaries of each self-beam coverage zone 211 may correspond to a corresponding self-beam coverage 210 at beam contour level 255-a, and the peak gain of each self-beam coverage zone 211 may have a location designated "x" (e.g., nominal alignment, or the axis of the corresponding own radiation pattern 210 of the irradiating elements, or the coverage area 211 of the own radiation pattern of the irradiating elements). Zones 211a-1, 211-a-2 and 211-a-3 of the coverage of the own radiation pattern of the irradiating elements can correspond to the projections of the own radiation patterns of the irradiating elements associated with the profiles 250-a-1, 250-a-2 and 250-a- 3 amplification of the own radiation pattern of the irradiating elements, respectively, and diagram 203 illustrates the amplification profiles 250 of the own radiation pattern of the irradiating elements along the section plane 260-a of the circuit 204.

The coverage areas 211 of the feed elements' own radiation pattern are referred to herein as idealized since the coverage areas are shown as circular for simplicity. However, in various examples, the coverage area 211 of the irradiating elements' own radiation pattern may have some shape other than a circle (eg, ellipse, hexagon, rectangle, etc.). Thus, the tile-based self-pattern coverage zones 211 may have more overlap with each other (e.g., in some cases, more than three tile-based self-pattern coverage zones 211 may overlap) than shown in diagram 204.

In diagram 204, which may represent a state in which the feed array node 127-a is in a defocused position with respect to the reflector 122-a, a substantial portion (e.g., the majority) of each coverage zone 211 of its own feed element radiation pattern overlaps with an adjacent zone. 211 covering the own radiation pattern of the irradiating elements. Locations within a service coverage area (e.g., the total coverage area of multiple spot beams of antenna assembly 121) may be within the native feed element coverage area 211 of two or more feed elements 128. For example, antenna assembly 121-a may be configured in this manner. , to maximize the area in which more than two coverage zones 211 of the irradiating elements' own radiation pattern overlap. In some examples, this condition may also be referred to as the presence of feed elements 128 of feed array node 127 or coverage areas 211 of the feed elements' own radiation pattern having a high degree of overlap. Although eight feed element self-pattern coverage zones 211 are illustrated, the feed array assembly 127 may have any number of feed elements 128 associated with the feed element self-pattern coverage zones 211 in a similar manner.

In some cases, a single antenna assembly 121 may be used to transmit and receive signals between user terminals 150 or access node terminals 130. In other examples, satellite 120 may include separate antenna assemblies 121 for receiving signals and transmitting signals. The receiving antenna assembly 121 of the satellite 120 may be directed to the same or similar service coverage area as the transmitting antenna assembly 121 of the satellite 120. Thus, some coverage areas 211 of the native feed element radiation pattern for the receiving antenna feed elements 128 are configured to receive. may naturally correspond to the coverage areas 211 of the intrinsic radiation pattern of the feed elements for the feed elements 128 configured to transmit. In these cases, the receiving feed elements 128 may be matched in a manner similar to their corresponding transmitting feed elements 128 (e.g., with similar array patterns of the various feed array nodes 127, with similar wiring and/or circuit connections to signal processing hardware, similar configurations, and /or software algorithms, etc.), which leads to similar signal paths and processing for transmitting and receiving coverage areas 211 of the irradiating elements' own radiation pattern. However, in some cases it may be advantageous to match the receiving feed elements 128 and the transmitting feed elements 128 in different ways.

A plurality of highly overlapped feed elements' own radiation patterns 210 may be combined through beamforming to provide one or more focused beams 125. Beamforming for the focused beam 125 may be accomplished by adjusting the phase of the signal or the time delay and/or amplitude of the signals for the signals. transmitted and/or received by several irradiating elements 128 of one or more nodes 127 of the irradiating array, having overlapping zones 211 covering the own radiation pattern of the irradiating elements. Such phase and/or amplitude adjustment may be referred to as the application of beam weights (eg, beamforming coefficients) to the feed element signals. For transmissions (e.g., from the transmitting feed elements 128 of the feed array assembly 127), the relative phases, and sometimes the amplitudes, of the signals to be transmitted are adjusted such that the energy transmitted by the feed elements 128 will be constructively superimposed at the desired location (e.g., at the location focused beam coverage area 126). For reception (e.g., by receiving feed elements 128 of feed array assembly 127, etc.), the relative phases and sometimes amplitudes of the received signals are adjusted (e.g., by applying the same or different beam weights) such that the energy received from desired location (eg, at the location of the focus beam coverage area 126) by the irradiating elements 128 will be structurally superimposed on the given focus beam coverage area 126.

The term "beamforming" can be used to refer to the application of beam weights for transmission, reception, or both. Calculating beam weights or coefficients may involve directly or indirectly detecting characteristics of a communication channel. The processes of calculating the beam weight and applying the beam weight can be performed in the same or different components of the system. Adaptive beamformers may include functionality that supports dynamic calculation of beam weights or coefficients.

The focused beams 125 can be directed, selectively shaped, and/or otherwise reconfigured by applying different beam weights. For example, the number of active self-patterns 210 of the feed elements or focus beam coverage areas 126, the size of the shape of the focus beams 125, the relative gain of the self-patterns 210 of the feed elements and/or focus beams 125, and other parameters may vary over time. Antenna assemblies 121 may employ beamforming to generate relatively narrow focused beams 125 and may generate focused beams 125 with improved gain characteristics. Narrow spot beams 125 may allow signals transmitted by one beam to be distinguished from signals transmitted by other spot beams 125 to, for example, avoid interference between transmitted or received signals or determine spatial separation of received signals.

In some examples, narrow spot beams 125 may allow frequency and polarization reuse to a greater extent than when forming large spot beams 125. For example, spot beams 125 that are narrowly formed may support signal transmission through non-contiguous spot beam coverage areas 126 that do not overlap, while the overlapping spot beams 125 may be orthogonal in frequency, polarization, or time. In some examples, greater reuse through the use of smaller spot beams 125 may increase the amount of data transmitted and/or received. In an additional or alternative embodiment, beamforming can be used to provide a sharper reduction in gain at the edge of the beam, which can provide higher beam gain over a larger portion of the focused beam 125. Thus, beamforming techniques can provide higher frequency reuse and/or greater system capacity for a given amount of system bandwidth.

Some satellites 120 may use OBBF to electronically control the signals transmitted and/or received through the feed element array 128 (eg, by applying beam weights to the feed element signals on the satellite 120). For example, satellite 120 may have built-in beamforming capability using a multi-feed per beam (MFPB) phased array antenna. In some examples, beam weights may be calculated at a ground computing center (eg, access node terminal 130, network device 141, communications service manager) and then transmitted to satellite 120. In some examples, beam weights may be preconfigured or otherwise defined on satellite 120 for airborne use.

In some cases, satellite 120 may require significant processing capability to control the phase and gain of each feed element 128 that is used to generate focused beams 125. Such processing power may increase the complexity of satellite 120. Thus, in some cases, satellite 120 may operate with GBBF to reduce the complexity of satellite 120 while providing the benefit of electronically shaping narrow focused beams 125. In some examples, beam weights or coefficients may be applied at ground segment 102 (e.g., at one or more ground stations) before transmitting the corresponding signals to satellite 120. which may include multiplexing the signals of the feed elements in the ground segment 102 in accordance with various time, frequency, or spatial multiplexing techniques, among other signal processing. Accordingly, satellite 120 may accordingly receive and in some cases demultiplex such signaling and transmit associated feed element signals through corresponding antenna feed elements 128 to form focused transmit beams 125 that are based at least in part on beam weights applied in ground segment 102. In some examples, satellite 120 may receive feed element signals through respective antenna feed elements 128 and transmit the received feed element signals to a ground segment 102 (e.g., one or more ground stations), which may include multiplexing the feed element signals on satellite 120 to according to various time, frequency or spatial multiplexing techniques, in addition to other signal processing. Ground segment 102 may accordingly receive and in some cases demultiplex such signaling and apply beam weights to the received feed element signals to create spot beam signals that correspond to corresponding spot beams 125.

In another example, the satellite system 100 in accordance with the present disclosure may support various end-to-end beamforming techniques, which may involve the formation of end-to-end spot beams 125 via satellite 120 or other vehicle operating as an end-to-end relay. For example, satellite 120 may include multiple signal transmission/reception paths (eg, repeaters), each of which is coupled between a receiving feed element and a transmitting feed element. In an end-to-end beamforming system, beam weights may be calculated at a central processing system (CPS) (eg, beamforming processor 135) of ground segment 102, and end-to-end beam weights may be applied within ground segment 102 rather than on satellite 120. Signals within end-to-end spot beams 125 may be transmitted and received within an array of access node terminals 130, which may be satellite access nodes (SANs). Any suitable type of end-to-end repeater can be used in an end-to-end beamforming system, and different types of access node terminals 130 can be used to communicate with different types of end-to-end repeaters.

The end-to-end beamformer within the CPS can compute one set of end-to-end beam weights that takes into account: (1) the uplink paths of the wireless signal up to the end-to-end repeater; (2) signal transmission/reception paths through an end-to-end repeater; and (3) the wireless signal downlink path from the end-to-end repeater. The beam weights can be represented mathematically as a matrix. In some examples, OBBF and GBBF satellite systems may have beam weight vector sizes given by the number of feed elements 128 on antenna node 121. Conversely, end-to-end beam weight vectors may have sizes given by the number of access node terminals 130 rather than the number of feed elements 128 on a pass-through repeater. Typically, the number of access node terminals 130 does not match the number of feed elements 128 on the end-to-end repeater. In addition, the generated end-to-end spot beams 125 terminate in neither the transmitting nor receiving feed elements 128 of the end-to-end repeater. Conversely, the generated end-to-end spot beams 125 can be effectively relayed because the end-to-end spot beams 125 can have uplink signal paths, relay signal paths (via satellite 120 or other suitable end-to-end relay) and downlink signal paths.

Because an end-to-end beamforming system can consider both a user link and a feeder link, as well as an end-to-end repeater, only one set of beam weights is required to form the required end-to-end spot beams 125 in a particular direction (e.g., forward spot beams 125 or reverse spot beams rays 125). Thus, one set of end-to-end forward spot beam weights causes the signals transmitted from the access node terminals 130 on the forward uplink, through the end-to-end repeater, and on the forward downlink to be combined to form end-to-end forward spot beams 125. Conversely, , signals transmitted from reverse users through the reverse uplink, through the end-to-end relay and the reverse downlink have end-to-end return beam weights applied to form the end-to-end return spot beams 125. Under some conditions, it may be difficult or impossible to distinguish the characteristics of the uplink communication and downlink communication. Accordingly, the generated spot beams 125 of the feeder link, the directionality of the generated spot beams, and the carrier-to-interference (C/I) ratio of the individual uplink and downlink links can no longer play their traditional role in system design, while the carrier-to-interference ratio concepts (Es/No) of uplinks, downlinks and end-to-end C/I ratio may still be important.

In fig. 5A and 5B illustrate an example of beamforming for forming spot beam coverage zones 126 over the antenna's own radiation pattern coverage zone 221-b in accordance with the examples disclosed herein. In fig. 5A, diagram 300 illustrates an antenna self-pattern coverage area 221-b, which includes multiple feed element self-pattern coverage areas 211 that can be provided by a defocused multi-feed antenna assembly 121. Each of the coverage areas 211 of its own feed element radiation pattern may be associated with a corresponding feed element 128 of the feed array node 127 of the antenna node 121. In FIG. 5B, diagram 350 shows a beam pattern of spot beam coverage areas 126 over service coverage area 310 in the continental United States. Focused beam coverage areas 126 may be provided by applying beamforming coefficients to signals transmitted by feed elements 128 associated with multiple feed elements' own beam pattern coverage areas 211 shown in FIG. 5A.

Each of the spot beam coverage areas 126 may have an associated spot beam 125, which, in some examples, may be based on a predetermined beamforming configuration configured to support a communications service or other primary or real-time target within corresponding focused beam coverage areas 126. Each of the focus beams 125 may be formed from a combination of signals transmitted by multiple feed elements 128 for those feed elements' own radiation pattern zones 211 that include a corresponding focus beam coverage area 126. For example, the spot beam 125 associated with the spot beam coverage area 126-c shown in FIG. 5B may be a combination of signals through eight feed elements 128 associated with the feed elements' own beam pattern coverage areas 211-b, shown as dark solid lines in FIG. 5A. In various examples, spot beams 125 with overlapping spot beam coverage areas 126 may be orthogonal in frequency, polarization, and/or time, while non-overlapping spot beams 125 may be non-orthogonal to each other (eg, a tile-based frequency reuse pattern). In other examples, non-orthogonal spot beams 125 may have varying degrees of overlap, with interference suppression techniques such as ACM, interference cancellation, or space-time coding used to control interbeam interference.

Beamforming can be applied to signals transmitted or received via satellite using OBBF, GBBF, or end-to-end beamforming signal paths. Thus, the service provided in the spot beam coverage areas 126 illustrated in FIG. 5B may be based on the coverage area 221-b of the antenna node 121's own antenna pattern, as well as the applied beam weights. Although service coverage area 310 is illustrated as being provided by a substantially uniform beam pattern of spot beam coverage areas 126 (e.g., having equal or substantially equal beam coverage area sizes and overlap amounts), in some examples of spot beam coverage areas 126 for service coverage area 310 may be uneven. For example, higher population density areas may provide communication service using relatively smaller spot beams 125, while lower population density areas may provide communication service using relatively larger spot beams 125.

In fig. 6 shows a diagram of a satellite system 600 that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. Satellite system 600 may include an illumination satellite 120a and multiple acquisition satellites 122. For example, satellite system 600 may include a GEO satellite 120-a and multiple collection satellites 122 (eg, collection satellites 122-c and 122-d). In some examples, satellite system 600 may include more than one lighting satellite 120, each of which may be in a similar orbit (eg, at different GEO orbital positions). The collection satellites 122 may be in a different orbit than the illumination satellite (eg, LEO or MEO).

The lighting satellite 120a may be a communications satellite and may transmit over multiple channels to create spot beams (eg, beamforming spot beams 125). In fig. 6 illustrates three spot beams: spot beams 125-a, 125-b and 125-c. Each of the spot beams 125 may be associated with a corresponding user beam coverage area 126. Because user beam coverage areas 126-a, 126-b, and 126-c are located adjacent to each other, each of the respective spot beams 125-a, 125-b, and 125-c may use a different combination of frequency range and polarization (e.g., " color"). For example, each of the spot beams 125-a, 125-b, and 125-c may be associated with the same polarization (eg, RHCP or LHCP) and may use a different frequency band or frequency range for the two spot beams 125-125-c. a, 125-b, and 125-c may be the same, and the two focused beams may use different (eg, orthogonal) polarizations.

The communications signals transmitted by satellite 120 can be used as an illumination source for a multistatic synthetic aperture radar. For example, direct downlink signals 170 may be reflected from surface 160 or objects 155 and received by collection satellites 122 in a multistatic configuration. As illustrated in FIG. 6, multiple collection satellites may have at least partially overlapping fields of view 620. In some examples, lighting satellite fields 620 may be configured to cover an area that may cover a limited number (e.g., one, two, etc.) of user beam coverage areas 126 associated with spot beams 125 having the same "color" " For example, user beam coverage areas 126 of spot beams of the same color may be separated by a separation distance, and fields of view 620 may be positioned to cover an area not exceeding a certain multiple of the separation distance. Collection satellites 122 may receive reflected signals 128 in a bandwidth range that includes each of the spot beams 125. For example, spot beams 125 may use a four-, five-, six-, seven-, or eight-color arrangement in which the frequency range, used to transmit beam signals 170 may be divided into two, three, or four subbands associated with different focused beams 125. Each of the collection satellites 122 can receive over the entire frequency range and in multiple polarizations and thus can simultaneously receive reflected signals 128 associated with various focused beams.

The collection satellites 122 may perform signal processing, including digitization (eg, sampling) and compression, and may send the sampled signals to the multistatic SAR processor 145 for processing. In some examples, acquisition satellites 122 may send sampled signals to multistatic SAR processor 145 via illumination satellite 120 (e.g., the same satellite that transmitted beam signals 125 for which it collects reflected beam signals 128). In some examples, lighting satellite 120 may be an end-to-end relay or may be used in a GBBF system, and collection satellites 122 may transmit reverse uplink signals over communication links 172 to lighting satellite 120 (e.g., collection satellite 122-c may transmit reverse uplink signals communication channel on communication channel 172-c, and the acquisition satellite 122-d may transmit reverse uplink signals on communication channel 172-d). The lighting satellite 120 may relay reverse uplink signals in reverse downlink signals (not shown) to one or more access node terminals (not shown). The access node terminals may receive the reverse downlink signals and send the reverse downlink signals to the beamforming processor 135 for processing. Beamforming processor 135 may reconstruct uplink beam signals (eg, including sampled return beam signals 128) transmitted by collection satellites 122 and transmit uplink beam signals to multistatic SAR processor 145. The beamforming processor 135 may also send the beamforming coefficients used in creating the beam signals 125 to the multistatic SAR processor 145 .

The multistatic SAR processor 145 may process the sampled return beam signals 128 from each of the acquisition satellites 122 to produce multistatic SAR data corresponding to the user beam coverage areas 126. For example, to obtain multi-static SAR data corresponding to a user beam coverage area 126-a, multi-static SAR processor 145 may filter sampled return beam signals 128 (e.g., corresponding to return beam signals 128-c and 128-d) for the frequency range associated with the signal 170-a focused beam. In addition, the multi-static SAR processor 145 may process the sampled return beam signals 128 in accordance with the gain profile of the user beam 125-a in the beam coverage area 126-a. For example, areas with higher signal strength may have larger weights in the processed signal. Spatial separation of multiple collection satellites can provide cross-path interferometry capabilities. Additionally, spatial and temporal separation of multiple collection satellites 122 can provide additional resolution. For example, a given user beam coverage area 126a may fall within the fields of view 620 of several different acquisition satellites 122 over a period of time. Multistatic SAR processor 145 can distinguish between different spot beam signals 170 based on the field of view as well as signal information (eg, beam signal). In some cases, multiple acquisition satellites, of which only two are shown, may pass over the user beam coverage area 126 at different times during a given time period. The multistatic SAR processor 145 may process the sampled beam returns 128 from each of the collection satellites 122 to provide different cross-path interferometry and time diversity to obtain image data associated with the returns in the user beam coverage area 126-a. In addition, different reflected signals may be obtained from signals transmitted by different lighting satellites 120 (eg, which may use different frequency bands or polarizations) of the same area. Multistatic SAR processor 145 may perform similar operations for each user beam coverage area 126 (e.g., user beam coverage areas 125-b and 125-c with spot beam signals 170-b and 170-d) and combine data from each user beam coverage area 126 beam to create an image of the desired geographic area (625).

In fig. 7 illustrates an example process flow diagram 700 that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. Process flow diagram 700 may be implemented in a satellite system 100 or 200. For example, process flow diagram may be implemented in a satellite system comprising a multistatic SAR processor 145-a, a beamforming processor 135-a, one or more access node terminals 130-a , one or more lighting satellites 120-a and one or more collection satellites 122-e. In some cases, one or more lighting satellites 120a may provide communication service for multiple user beam coverage areas through multiple user spot beams and may be a GEO satellite. One or more acquisition satellites 122 may be LEO or MEO satellites.

Illumination satellite 120-a may transmit a beacon signal 180-a, which can be used by collection satellites 122-a as a frequency and/or phase reference. For example, acquisition satellites 122 may synchronize timing with beacon signal 180 a to determine phase information for the received reflected signals.

Beamforming processor 135-a may receive forward link (FL) beam signals at step 705. For example, downlink data intended for user terminals may be determined and formed (eg, encoded, modulated) into FL beam signals for transmission in a given time period (for example, in a position or in a time period). At step 710, beamforming processor 135-a may apply beamforming coefficients to the FL beam signals to obtain FL AN signals 720. For example, the AN FL signals 720 may be signals corresponding to satellite feed elements 120-b for GBBF, or may be signals to be transmitted by access node terminals 130-a in an end-to-end beamforming system. Beamforming processor 135-a may provide AN FL signals 720 to access node terminals 130-a.

The access node terminals 130-a may transmit forward uplink (F-UL) signals 725 based on the AN FL signals 720 received from the beamforming processor 135-a. Satellite 120-b may receive F-UL signals 725 and transmit forward downlink (F-DL) signals 730, which may form spot beams based on beamforming coefficients applied by beamforming processor 135-a. For example, in a GBBF system, each channel of satellite 120-b may transmit a signal received from access node terminal 130-a, which may be combined to form spot beams. Alternatively, in an end-to-end beamforming system, satellite 120-b may include multiple transmit/receive signal paths, and each transmit/receive signal path may transmit composite F-UL signals 725 received from one or more access node terminals 130-a .

F-DL signals 730 forming spot beams carrying beam signals may be reflected from surface 160-b as reflected beam signals 732 and may be received by collection satellites 122-e. The collection satellites 122-e may sample the beam returns 732 and send the sampled beam returns 732 to the multi-static SAR processor 145-a for processing. The collection satellites 122 e may also receive the F-DL signals 730 directly (eg, not reflected) and may use the F-DL signals 730 to determine various information for the sampled reflected beam signals 732 . For example, in an additional embodiment, or as an alternative to using the beacon signal 180-a, collection satellites 122-e may use the F-DL signals 730 as a reference for determining the frequency, phase, or arrival time of the reflected beam signals 732. In addition, collection satellites 122 may use F-DL signals 730 to determine atmospheric corrections or consistency for the reflected beam signals 732. Collection satellites 122-e may transmit reverse uplink (R-UL) signals 745 containing sampled beam returns to satellite 120-b (which in some cases may be the same satellite as the lighting satellite, or a different satellite ). Satellite 120-b may relay R-UL signals in R-DL signals 755 to access node terminals 130-a. The access node terminals 130-a may receive and process (eg, sample) the R-DL signals 755 and send the RL signals 760 containing the sampled R-DL signals 755 to the beamforming processor 135-a.

Beamforming processor 135-a may apply RL beam coefficients to RL signals 760 at step 775. For example, in a GBBF system, each satellite receive signal 120-b may be in a separate R-DL signal 755. Alternatively, in an end-to-end beamforming system, satellite 120-b may relay R-UL signals 745 over multiple signal paths, and thus each R-DL signal 755 received by access node terminal 130-a may represent a composite signal including signals from multiple RL spot beams carried by at least a subset of multiple signal transmission/reception paths of satellite 120-b. Thus, beamforming processor 135-a can receive composite signals from each of the multiple access node terminals 130-a and apply RL beamforming coefficients representing end-to-end beamforming matrices between the RL beams and the multiple access node terminals 130-a to reconstruct the signals. beam RL. Beamforming processor 135-a may send RL beam signals to multi-static SAR processor 145-a for processing.

Multistatic SAR processor 145-a may obtain sampled return beam signals 732 from RL beam signals 780. Alternatively, multistatic SAR processor 145-a may receive sampled beam returns 732 via a different route. For example, collection satellites 122-e may transmit sampled beam returns directly to a ground station (not shown). The multi-static SAR processor 145-a may process the sampled beam returns 732 from each of the acquisition satellites 122-e to produce multi-static SAR data corresponding to the user beam coverage areas of the F-DL signals 730. Multistatic SAR processor 145-a may also obtain signal information for F-DL signals 730 from beamforming processor 135-a. For example, beamforming processor 135-a may provide FL beam signals 765 to multistatic SAR processor 145-a. In addition, beamforming processor 135-a may provide beam coefficients 770 to multi-static SAR processor 145-a.

Multistatic SAR processor 145-a may process the sampled return beam signals 732 based on FL beam signals 765 and beam coefficients 770 at step 785. For example, for a given FL beam generated by illumination satellite 120-b, multistatic SAR processor 145-a may estimate the sampled reflected beam signals 732 from each collection satellite 122-e having a field of view, including portions of the FL beam and the entire FL beam. For example, multistatic SAR processor 145-a may use beam coefficients 770 to determine FL beam properties, including gain profile, and may use FL beam signals 765 to determine radar information (e.g., range, reflectivity) associated with reflected beam signals 732 due to the terrain or objects encountered by the 730 F-DL signals. Multi-static SAR processor 145-a may use sampled beam returns 732 corresponding to simultaneous (eg, phase-correlated) F-DL signals 730 from multiple collection satellites 122-e to increase range and accuracy. In addition, the multistatic SAR processor 145-a may use sampled beam returns 732 from multiple acquisition satellites 122-e to obtain a synthetic aperture corresponding to the image information associated with the FL beam. Thus, multistatic SAR processor 145-a can construct a beam coverage image for each FL beam based on sampled beam returns 732 from multiple acquisition satellites 122-e that have fields of view at least partially overlapping with the beam coverage during a certain period of time. For example, multi-static SAR processor 145-a may determine the extent to which the field of view for each collection satellite 122-e overlaps with the beam coverage area and apply a beam overlap and gain profile to weight the sampled beam return 732 from each of the collection satellites 122-e for each instant. time.

In fig. 8 shows a schematic diagram of a multi-static SAR processor 145-b that supports multi-static synthetic aperture radar operating techniques using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. The multistatic SAR processor 145-b may include a multistatic SAR signal detector 810, a SAR beam signal detector 820, a SAR beam signal processor 830, and an image processor 840. Each of these modules may communicate with each other directly or indirectly (eg, through one or more buses).

Multistatic SAR signal detector 810 may receive sampled return signals of beam 805 in a multistatic system with one or more illumination satellites and one or more collection satellites. For example, one or more of the illumination satellites may be GEO satellites, and the acquisition satellites may be in a different orbit (eg, LEO or MEO). The one or more lighting satellites may be communications satellites and may transmit over multiple channels to create focused beams. Spot beam signals can be reflected from terrain and objects, and the reflected signals can be received and sampled by collection satellites. Collection satellites may use the beacon signal (eg, beacon signal 180) or the spot beam signals themselves (eg, direct, non-reflected spot beam signals) as a reference for determining the frequency, phase, or arrival time of the reflected beam signals. The multistatic SAR signal detector 810 may process the sampled beam returns 805 to obtain signal information for each of the multiple focused beams (eg, based on frequency range, polarization, or field of view of the collection satellites). The multi-static SAR signal detector 810 may provide spot beam signal information 815 to the SAR beam signal detector 820 .

The SAR beam signal detector 820 may receive focused beam signal information 815 from the multistatic SAR signal detector 810. SAR beam signal detector 820 may also receive beam information 822, which may include beam signals or beam coefficients (eg, beamforming matrix 823 used to form forward downlink beams) associated with beamforming focused beams. The SAR beam signal detector 820 may, for each beam coverage area, determine return signal information (eg, range, reflectivity) based on the focused beam signal information 815 and the beam information 822. For example, the SAR beam signal detector 820 may determine return signal information for each beam signal received at each acquisition satellite and send the return signal information 825 to the SAR beam signal processor 830. For example, SAR beam signal detector 820 may determine reflected signal information 825 based on the gain profiles of the focused beam signal and the beam signal.

The SAR beam signal processor 830 may receive the return signal information 825 and may determine image information associated with each focus beam coverage area based on the return signal information 825. The SAR beam signal processor 830 may apply interferometry from the return signal information 825 from different collection satellites and may further synthesize an aperture to form images within each focus beam coverage area based on the return signal information from multiple collection satellites over different periods of time. For example, SAR beam signal processor 830 may receive information for the location of acquisition satellites at each instant in time to synthesize an aperture using multiple acquisition satellites, as well as multiple acquisition satellites over time. The SAR beam signal processor 830 may transmit beam image information 835 to the image processor 840 .

The image processor 840 may create an image 850 from the beam image information 835 . For example, image processor 840 may combine beam image information 835 for different beam coverage areas or assign image properties (eg, brightness, hue) to image pixels based on beam image information 835.

In fig. 9 shows a diagram of a system 900 comprising a device 905 that supports multistatic synthetic aperture radar techniques in accordance with the examples disclosed herein. Apparatus 905 may be an example of or include components of a reception processing system as described herein. The device 905 may include components for bidirectional communication, including components for sending and receiving messages, including a multistatic SAR processor 910, an input/output (I/O) controller 915, a database controller 920, a storage device 925, a processor 930, and a database 935 These components may communicate electronically via one or more buses (eg, bus 940).

Multistatic SAR processor 910 may be an example of multistatic SAR processor 145 as described herein. In some cases, the multistatic SAR processor 910 may be implemented in hardware, software executed by the processor, firmware, or any combination thereof. For example, multistatic SAR processor 910 may receive sampled beam returns (eg, through I/O controller 915) and process the sampled beam returns to create multistatic synthetic aperture radar images. The sampled reflected beam signals may correspond to signals received by one or more collection satellites, and may be received by the system 900 via a satellite (eg, an illumination satellite) or directly from the collection satellite to a ground station. Multi-static SAR processor 910 may process the sampled beam returns in accordance with beam information (eg, beam signals, beam coefficients) to obtain beam information for each of the collection satellites over a period of time. The multistatic SAR processor 910 may create image pixel values (eg, intensity, hue) based on the processed beam information and additional information related to the acquisition satellites (eg, location, atmospheric correction). Multistatic SAR processor 910 may output images in output signals 950 via I/O controller 915 (eg, for display on a display device or storage on a storage medium).

I/O controller 915 may control input signals 945 and output signals 950 to device 905. I/O controller 915 may also control peripheral devices not integrated into device 905. In some cases, I/O controller 915 may represent a physical connection or port with external peripheral device. In some cases, the 915 I/O controller may use an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX® or other known operating system. In other cases, the I/O controller 915 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, the I/O controller 915 may be implemented as part of the processor. In some cases, a user may interact with device 905 through I/O controller 915 or through hardware components controlled by I/O controller 915.

The database controller 920 may control the storage and processing of data in the database 935 . In some cases, the user may interact with the database controller 920. In other cases, the database controller 920 may operate automatically without user interaction. The database 935 may be an example of a single database, a distributed database, multiple distributed databases, a data warehouse, a data lake, or a disaster backup database. The database 935 may, for example, store multiple sets of beam weights for use by the multistatic beamforming system 910.

Storage device 925 may include random access memory (RAM) and read only memory (ROM). Memory device 925 may store computer-readable, computer-executable software, including instructions that, when executed (eg, by processor 930) cause the processor to perform various functions described herein. For example, memory 925 may store instructions for operations of the multistatic SAR processor 910 described herein. In some cases, storage device 925 may include, among other things, a basic input/output system (BIOS), which may control basic hardware or software operations, such as interaction with peripheral components or devices.

Processor 930 may include an intelligent hardware device (e.g., a general purpose processor, DSP, central processing unit (CPU), microcontroller, ASIC, FPGA, programmable logic device, discrete gate or transistor logic component, discrete hardware component, or any combination thereof). In some cases, processor 930 may be configured to operate on the memory array using a storage controller. In other cases, the storage controller may be integrated into the processor 930. The processor 930 may be configured to execute computer-readable instructions stored in the storage device 925 to perform various functions.

In fig. 10 is a block diagram illustrating a method 1000 that supports a multistatic synthetic aperture radar using low-Earth orbit data acquisition, in accordance with the examples disclosed herein. The operations of method 1000 may be implemented by a satellite system or components thereof, as described herein. For example, the operations of method 1000 may be performed by satellite system 100 or satellite system 600. In some examples, components of the satellite system may execute a set of instructions to control functional elements of the satellite system to perform the functions described below. Additionally or alternatively, satellite system components may perform aspects of the functions described below using special purpose hardware.

At step 1005, a first satellite of the satellite system may transmit a first set of forward downlink signals through an antenna covering a geographic region, wherein each of the first set of forward downlink beams within the geographic region is formed from at least a subset of the first set of forward downlink signals. communications. Transmitting a first plurality of forward downlink signals from a first satellite may include applying, at the first satellite, a first beamforming matrix to a plurality of forward uplink signals received from the satellite access node to obtain a first plurality of forward downlink signals. Alternatively, transmitting the first plurality of forward downlink signals from the first satellite may include transmitting from a plurality of satellite access nodes corresponding forward uplink signals and relaying, over a plurality of signal transmission/reception paths of the first satellite, corresponding forward uplink signals, wherein each of the first plurality of forward downlink signals comprises a composite element of at least a subset of corresponding forward uplink signals. The first set of forward downlink signals may be beam signals carrying communication data for user terminals on the first set of forward downlink beams. The first satellite may be a GEO satellite. The operations at step 1005 may be performed in accordance with methods described herein. In some examples, aspects of the operations in step 1005 may be performed by lighting satellite 120, as described with reference to FIG. 1 or 6.

At step 1010, the set of second satellites may receive respective first signals including reflections of the first set of forward downlink beams. The second set of satellites may be LEO or MEO satellites. The operations at step 1010 may be performed in accordance with methods described herein. In some examples, aspects of operations 1010 may be performed by collection satellites 122, as described with reference to FIG. 1 or 6.

At step 1015, the multistatic SAR processor may determine components of at least a subset of corresponding first signals associated with each of the set of forward downlink beams based on the signal data of each of the set of forward downlink beams. For example, the first plurality of forward downlink beams may comprise a plurality of forward downlink beams having a first combination of polarization and frequency range, and at least a subset of the respective first signals may comprise corresponding composite reflections from the plurality of forward downlink beams having the first combination polarization and frequency range. The operations at block 1015 may be performed in accordance with methods described herein. In some examples, aspects of the operations in step 1015 may be performed by a SAR beam signal detector, as described with reference to FIG. 8.

At step 1020, the multistatic SAR processor may process, based on the first beamforming matrix used to form the first set of forward downlink beams, the corresponding first signals received by the set of second satellites to obtain an image of the geographic region. Processing of the respective first signals received by the set of second satellites to produce an image may be based on the beam signals from the first set of forward downlink beams. The operations at block 1020 may be performed in accordance with methods described herein. In some examples, aspects of the operations at block 1020 may be performed by SAR beam signal processor 830, as described with reference to FIG. 8.

Aspects of steps 1005, 1010, 1015, or 1020 may be performed over multiple durations of time. For example, a first satellite may transmit a second plurality of forward downlink signals corresponding to a second duration of time, wherein the second plurality of forward downlink signals forms a second plurality of forward downlink beams over a geographic region. A plurality of second satellites may receive respective second signals comprising reflections of a second plurality of forward downlink beams. A multistatic SAR processor may process corresponding second signals received by a plurality of second satellites to produce an image of a geographic region. The processing of the respective second signals may be based on the same beamforming matrix that was used to create the first set of forward downlink signals, or in some cases on a second, different beamforming matrix.

It should be noted that the techniques described are representative of possible implementations and that the operations and components may be rearranged or otherwise modified, and that other implementations are possible. Additional parts of two or more of their methods or devices may be combined.

The information and signals described herein may be represented using any of a variety of different technologies and methods. For example, data, instructions, commands, information, signals, bits, symbols and chips that may be mentioned in the description may be voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or implemented with a general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other programmable a logic device, discrete or transistor logic circuit, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (eg, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other similar configuration).

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium. Other examples and embodiments are included within the scope of the invention and the accompanying claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, a hardware implementation, or a combination of any of the foregoing. Elements that implement functions may also be physically located in different positions, including being distributed in such a way that portions of the functions are implemented in different physical locations.

Computer-readable media includes both non-volatile computer storage media and communications media, including any media that facilitates transfer of a computer program from one location to another. A non-volatile storage medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-volatile computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disc (CD) ROM, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-volatile medium that can be used to carry or store required program code facilities in the form of instructions or data structures that can be accessed by a general purpose or special purpose computer or general purpose or special purpose processor. Additionally, any connection is properly referred to as a computer readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair cable, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then coaxial cable , fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwave are included in the definition of media. The disc and disc used herein include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where discs generally reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of the above are also included in the scope of machine-readable media.

As used herein, including in the claims, the term “or” when used in a list of elements (for example, in a list of elements preceded by a phrase such as “at least one of” or “one or more of”) means including a list such as, for example, a list of "at least one of A, B or C" means A or B or C or AB or AC or BC or ABC (i.e. A, B and C ). In addition, as used herein, the phrase “based on” should not be construed as a reference to a closed set of terms. For example, the exemplary step described by the phrase "based on condition A" may be based on both condition A and condition B without departing from the scope of the present invention. In other words, as used herein, the phrase “based on” should be interpreted in the same way as the phrase “based on at least in part.”

In the accompanying figures, similar components or elements may be designated by the same reference numerals. In addition, different components of the same type can be distinguished by a hyphen following the reference position and a second label that distinguishes them from similar components. If only the first reference numeral is used in a specification, the description applies to any of the similar components having the same first reference numeral, regardless of the second reference numeral or other subsequent reference numeral.

The description set forth herein in connection with the accompanying drawings describes typical configurations and does not represent all examples that may be implemented or that are within the scope of the claims. As used herein, the term “exemplary” means “serving as an example, example, or illustration” and not “preferred” or “superior to other examples.” The detailed description includes specific details in order to provide an understanding of the methods described. However, these methods can be put into practice without these specific details. In some cases, well-known structures and devices are shown in block diagram form to facilitate understanding of the concepts of the described examples.

The description herein is provided to enable one skilled in the art to make or use the present invention. Various modifications of the invention will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the present invention. Thus, the invention is not limited to the examples and designs described herein, but is intended to have the widest scope consistent with the principles and novel features disclosed herein.

Claims (36)

1. A method for obtaining an image of a geographic region, including: transmitting from the first satellite (120) a first plurality of forward downlink signals (170) via an antenna (121) covering a geographic region (625), wherein each of the first plurality of forward downlink beams (125) within a geographic region (625 ) is formed from at least a subset of the first set of forward downlink signals (170); the plurality of second satellites (122) receiving corresponding first signals (128) containing reflections of the first plurality of forward downlink beams (125); processing based at least in part on a first beamforming matrix (823) used to form a first plurality of forward downlink beams (125) corresponding to first signals (128) received by the plurality of second satellites (122) to obtain an image ( 850) geographic region (625). 2. The method according to claim 1, characterized in that the first plurality of forward downlink beams (125) comprises a plurality of forward downlink beams (125) having a first combination of polarization and frequency range, wherein at least a subset of the corresponding first signals (128) contain corresponding composite reflections from a plurality of forward downlink beams (125) having a first combination of polarization and frequency range, wherein the processing includes: determining components of said at least a subset of corresponding first signals (128) associated with each of the plurality of forward downlink beams (125) based at least in part on signal data from each of the plurality of forward downlink beams (125). 3. The method according to claim 1 or 2, characterized in that the first set of forward downlink signals (170) corresponds to the first time duration, the method further comprising: transmitting from the first satellite a second plurality of forward downlink signals (170) corresponding to a second duration of time, wherein the second plurality of forward downlink signals (170) form a second plurality of forward downlink beams (125) over a specified geographic region (625) ; the plurality of second satellites (122) receiving corresponding second signals (128) containing reflections of a second plurality of forward downlink beams (125); processing, based at least in part on a second beamforming matrix (823) used to form a second plurality of forward downlink beams (125), corresponding second signals (128) received by the plurality of second satellites (122), to obtain an image ( 850) geographic region (625). 4. The method according to claim 3, characterized in that the first plurality of beams (125) of the forward downlink are associated with a first beam coverage diagram comprising a first plurality of beam coverage zones (126) associated with a first polarization and a first frequency range, and a second a plurality of forward downlink beams (125) are associated with a second beam coverage diagram comprising a second set of beam coverage zones (126) associated with a first polarization and a first frequency range, wherein the second set of beam coverage zones (126) are offset relative to the first set of zones (126) beam coverage. 5. The method according to claim 3, characterized in that the first set of beams (125) of the forward downlink is associated with a first beam coverage diagram containing a first beam coverage area (126) associated with a first combination of polarization and frequency range, and the second set forward downlink beams (125) are associated with a second beam coverage diagram comprising a second beam coverage area (126) associated with a second polarization and frequency range combination, wherein the second beam coverage area (126) substantially overlaps with the first beam coverage area (126). ) beam coverage. 6. Method according to any one of paragraphs. 1-5, characterized in that the transmission of a first plurality of forward downlink signals (170) from the first satellite (120) includes: applying to the first satellite (120) a first beamforming matrix (823) to a plurality of forward uplink signals (175) received from the satellite access node (130) to obtain a first plurality of forward downlink signals (170). 7. Method according to any one of paragraphs. 1-5, characterized in that the transmission of a first plurality of forward downlink signals (170) from the first satellite (120) includes: transmitting from a plurality of satellite access nodes (130) corresponding forward uplink signals (175); And relaying, through a plurality of first satellite signal transmission/reception paths (120), corresponding forward uplink signals (175), wherein each of the first plurality of forward downlink signals (170) comprises a combination of at least a subset of corresponding forward uplink signals (175) communication channel. 8. Method according to any one of paragraphs. 1-7, wherein the first plurality of forward downlink signals (170) comprise a plurality of forward user data streams for transmission to a plurality of user terminals (150) within a geographic region (625). 9. Method according to any one of paragraphs. 1-8, wherein the first satellite (120) is a geostationary (GEO) satellite and the plurality of second satellites (122) are low-Earth orbit (LEO) satellites. 10. An imaging system comprising: a first satellite (120) configured to transmit a first plurality of forward downlink signals (170) via an antenna (121) covering a geographic region (625), wherein each of the first plurality of forward downlink beams (125) within a geographic region (625) is formed from at least a subset of the first set of forward downlink signals (170); a plurality of second satellites (122) configured to receive corresponding first signals (128) containing reflections of a first plurality of forward downlink beams (125); And at least one processor configured to process, based at least in part on a first beamforming matrix (823) used to generate a first plurality of forward downlink beams (125), corresponding first signals (128) received by the plurality of second satellites (122) to obtain images (850) of a geographic region (625). 11. The imaging system of claim 10, wherein the first plurality of forward downlink beams (125) comprises a plurality of forward downlink beams (125) having a first combination of polarization and frequency range, and at least a subset of the corresponding first signals (128) comprises corresponding composite reflections from a plurality of beams (125) of a forward downlink communication channel having a first combination of polarization and frequency range, wherein said at least one processor is configured to determine components of said at least a subset of corresponding first signals (128 ) associated with each of the plurality of forward downlink beams (125), based at least in part on signal data from each of the plurality of forward downlink beams (125). 12. The imaging system according to claim 10 or 11, characterized in that the first set of forward downlink signals (170) correspond to the first time duration, wherein: the first satellite (120) is configured to transmit a second plurality of forward downlink signals (170) corresponding to a second duration of time, wherein the second plurality of forward downlink signals (170) forms a second plurality of forward downlink beams (125) over a geographic region (625); a plurality of second satellites (122) configured to receive corresponding second signals (128) containing reflections of a second plurality of forward downlink beams (125); And said at least one processor configured to process, based at least in part on a second beamforming matrix (823) used to form a second plurality of forward downlink beams (125), corresponding second signals (128) received by the plurality of second satellites (122) to obtain images (850) of a geographic region (625). 13. The imaging system of claim 12, wherein the first plurality of forward downlink beams (125) are associated with a first beam coverage diagram comprising a first plurality of beam coverage zones (126) associated with a first polarization and a first frequency range, and a second plurality of forward downlink beams (125) are associated with a second beam coverage diagram comprising a second plurality of beam coverage zones (126) associated with a first polarization and a first frequency range, wherein the second plurality of beam coverage zones (126) are offset relative to the first multiple beam coverage zones (126). 14. The imaging system of claim 12, wherein the first plurality of forward downlink beams (125) are associated with a first beam coverage pattern comprising a first beam coverage area (126) associated with a first polarization and frequency range combination, and a second set of forward downlink beams (125) is associated with a second beam coverage diagram comprising a second beam coverage area (126) associated with a second polarization and frequency range combination, wherein the second beam coverage area (126) substantially overlaps with the first area (126) beam coverage. 15. Imaging system according to any one of claims. 10-14, characterized in that the first satellite (120) is configured to apply a first beamforming matrix (823) to a plurality of forward uplink signals (175) received from a satellite access node (130) to obtain a first plurality of signals ( 170) direct downlink communication channel. 16. Imaging system according to any one of claims. 10-14, additionally containing: a plurality of satellite access nodes (130) configured to transmit corresponding direct uplink signals (175), wherein the first satellite (120) comprises a plurality of signal transmission/reception paths configured to relay corresponding forward uplink signals (175), wherein each of the first plurality of forward downlink signals (170) comprises a combination of at least a subset of the corresponding signals (175) of the forward uplink. 17. Imaging system according to any one of claims. 10-16, wherein the first plurality of forward downlink signals (170) comprise a plurality of forward user data streams for transmission to a plurality of user terminals (150) within a geographic region (625). 18. The imaging system according to any one of claims. 10-17, wherein the first satellite (120) is a geostationary (GEO) satellite and the plurality of second satellites (122) are low-Earth orbit (LEO) satellites.