RU2017168C1 - Method for space-based synthetic-aperture radar detection of terrain targets - Google Patents

Abstract

FIELD: radio detection and ranging. SUBSTANCE: target detection means has synthetic-aperture radar (SAR) 1, target receiver-transmitter (TRT) 2, ranging signal driver 3, SAR transmitter 4, SAR antenna 5, SAR receiver 6, SAR transmit-receive switch, SAR receiver 7, SAR receiver input processor, target-present position display 9, TRT antenna 10, TRT transmit-receive switch 11, TRT receiver 12, decoder 13, frequency- controlling oscillator 14, TRT transmitter 15, 3-4-6-7-8- 9, 10-11-12-13-14-15-11, 6-5. EFFECT: increased efficiency. 1 dwg

Description

 The invention relates to radar, in particular to the use of a radar method with an active response in space or airborne radars.

 A known method of using radar means with an active response in the form of a system of radar beacons for air traffic control ATCRBS, which includes ground-based radar and radar transponders on aircraft. Using the ATCRBS system provides recognition of aircraft with an indication of their position in three-dimensional space.

 The disadvantage of this method is that when it is used at large distances between the radar and the transponder, a relatively high power transmitter must be installed on the transponder object. For example, a transmitter at an ATCRBS transponder with a range of about 370 km requires 500 W output power. For space systems, where operating ranges are thousands of kilometers, radiation powers of tens to hundreds of kilowatts or the use of relatively large directional antennas at the transponder will be required.

A known method for determining the location of objects on the surface of the Earth using a radar with a synthesized antenna (SAR) space or air based. The method is based on the radiation of a probe signal by the SAR device in the direction of the observed region on the Earth’s surface during the synthesis time T _s , reception of its reflected part from the earth’s surface and objects located on it, coherent processing on the time interval T _s and display as a radar image ( RLI), characterizing the location of concentrated objects on the Earth's surface (provided that the power of the signal reflected from the object exceeds the total noise and background power).

 The disadvantage of this method is that with real-world resolution achievable in space and aircraft SARs, small objects (with linear dimensions of several meters) cannot be identified with a high level of recognition probability. Experimental studies in different ranges show that for recognizing an object with a probability of 0.9, such a level of destruction on the terrain is necessary that 12-14 resolution elements fit into the linear size of the recognized object. For reliable recognition of an object with critical dimensions of the order of 3 m, it is necessary to provide a resolution of 0.2-0.24 m, which is unattainable so far.

 The aim of the invention is to increase the likelihood of recognition of small objects during their observation of space-based or airborne SAR.

This is achieved by the fact that the moving object, the location of which must be controlled, receive the probing signal PCA for a time t ₁ <T _c , decrypting it to make a decision according to the probing signal for this particular object (the cipher about the requested object is specified in the probing signal by its modulation, for example, phase intrapulse, pulse-code, frequency, etc.), storing up to phase, amplification and radiation over time t _z ≃ T _s , receiving its SAR, coherent processing and sampling Reference in the form of a coordinate mark from the object.

A distinctive feature of this method compared to the prototype is that in the PCA, the signal is encrypted and emitted in the direction of the object for a time t ₁ <T _c , it is received at the object, decrypted, stored up to phase and the radiation during t _z ≃T _c .

 The effect of using the proposed method lies in the fact that the probability of recognition of small objects, which when using the prototype method in modern SARs, is practically zero, when the corresponding energy ratios are equal to 1, since there will be a mark only from that object on the radar to which the request is made by applying the appropriate probe signal code, thereby eliminating the erroneous decision.

 The accuracy of determining the coordinates of a moving object when using the proposed method is mainly determined by the accuracy of the navigation measurement of the motion parameters of the SAR carrier and pointing the SAR antenna, and when using reference beacons (transceivers that are located at points with known coordinates) - radar data.

, где Р_и - импульсная мощность передатчика РСА;
А_2эф - эффективная площадь антенны приемопередатчика;
G₁ - коэффициент усиления антенны РСА;
R - дальность наблюдения;
обеспечение мощности излучения передающего устройства Ротв приемопередатчика, необходимого для получения отметки от объекта на РЛИ с заданным отношением сигнал/шум:
P_отв=

, где q - требуемое отношение сигнал/шум на выходе устройства обработки РСА;
k - постоянная Больцмана;
Т_э - эффективная температура приемника РСА;
Ш - коэффициент шума приемника РСА;
Δf - полоса пропускания приемника РСА;
L - суммарные энергетические потери;
N - количество когерентно суммируемых импульсов в устройстве обработки РСА;
А_1эф - эффективная площадь антенны РСА;
G_z - коэффициент усиления антенны приемопередатчика.The main characteristics of the transceiver installed on the site are determined from the following requirements:
ensuring stable reception of the probe signal, the power of which at the input of the receiver of the transceiver is calculated in accordance with the expression
P _ol =

where P _and is the pulse power of the SAR transmitter;
And _2eff is the effective area of the antenna of the transceiver;
G ₁ - gain antenna PCA;
R is the observation range;
providing the radiation power of the transmitting device Rotv transceiver, necessary to obtain a mark from the object on the radar with a given signal to noise ratio:
P _resp =

where q is the required signal-to-noise ratio at the output of the SAR processing device;
k is the Boltzmann constant;
T _e is the effective temperature of the SAR receiver;
W - noise figure of the SAR receiver;
Δf is the passband of the SAR receiver;
L - total energy loss;
N is the number of coherently summed pulses in a PCA processing device;
And _1eff is the effective area of the SAR antenna;
G _z is the gain of the antenna of the transceiver.

где E_о- амплитуда радиоимпульса;
U_д- амплитуда модуляции;
T_д- длительность дискрета;
Ψ_к = 0,π- начальная фаза дискрета;
ω_о- несущая частота;
φ_о- начальная фаза радиоимпульса;
T_о- длительность радиоимпульса.As a probing signal, in which information about the number of the requested object is encrypted, as one of the options, you can use a rectangular code-manipulated (CPM) pulse. Such a pulse is a sequence of single simple radio pulses adjacent to each other with the same frequencies, the same duration and the initial phases, changing from pulse to pulse according to the code law. In an analytical form, such a radio pulse can be represented by the expression
u (t) =

where E _about - the amplitude of the radio pulse;
U _d - the amplitude of the modulation;
T _d - the duration of the discrete;
Ψ _k = 0, π is the initial phase of the discrete;
ω _about - carrier frequency;
φ _about - the initial phase of the radio pulse;
T _about - the duration of the radio pulse.

The number of discretes in the pulse h _d = T _o / T _d is selected depending on the number of objects / for which work is expected (for each object its own codephase manipulation is set).

Another option is also possible to encrypt the object number when using a time-limited packet of simple radio pulses / in which, by blanking the corresponding pulses inside the packet, the object number code is generated
In FIG. 1 shows a structural diagram of a device for implementing the proposed method.

 It contains a radar 1 with a synthesized antenna (PCA), a transceiver (PPU) 2 at the site, a device 3 for generating a sounding signal, a transmitter 4 PCA, antenna 5 PCA, switch 6 transmit-receive PCA, receiver 7 PCA, device 8 processing PCA signals, device 9 for displaying and determining coordinates, antenna 10 for PPU, switch 11 for transmitting and receiving PPU, receiver 12 for PPU, decoder 13, controlled local oscillator 14, transmitter 15 for PPU.

The probe signal generated in block 3, which includes information about the number of the requested object, after amplification in the transmitter 4 is emitted through the antenna 5 into space, received by the antenna 10 on the receiver, amplified in the receiver 12, and analyzed in the decoder 13. If the probe signal code matches the number of the object is the storage of the received signal accurate to the phase in the controlled local oscillator, its amplification and radiation through the antenna 10 into space. The emitted PPU signal is received by the antenna 5, amplified in the receiver 7, processed on the synthesis interval T _with in block 8 and fed to the device 9, where it is displayed and coordinates are determined.

 The proposed method can be used in the national economy in solving the problem of monitoring the use of moving objects.

Claims (1)

METHOD FOR DETERMINING THE LOCATION OF OBJECTS ON GROUND USING synthetic aperture radar AEROSPACE BASING comprising that emit radar sounding radio signal receiving radar radio signal from the object for a time T _s, equal to the interval of the synthetic aperture radar, is treated with the received radio signal over a time interval T _with aperture synthesizing method and displayed on the radar indicator in the form of characterizing the location of the object, coordinate mark, characterized in that the radiation radar probe is previously encrypted before radiation, emitted for a time t <T _s , the emitted radio signal is received at the object, followed by its interpretation, storing up to phase, amplification and radiation into space over time T _{from the} radio signal of the corresponding object.