CN108173007A - A double-layer waveguide slot near-field focusing array antenna based on four-corner feeding - Google Patents

Abstract

A kind of double-deck Waveguide slot near field focus array antenna based on quadrangle feed, is related to a kind of Waveguide slot antenna.It is made of the feed waveguide of lower floor and the radiating guide on upper strata；Incidence wave passes through feed waveguide successively from feed port, couple gap, radiating guide, space is finally radiated outside by radiating slot, the feed port and feed waveguide pass through central aperture feed-in using standard feed waveguide from the back side, it is fed using quadrangle and replaces traditional apex drive, by having the feed waveguide of 4 arms that signal is extended to 4 antenna angles from center, it is fed in the same direction from both ends to intermediate constant amplitude, PMC boundaries can be formed in feed waveguide center, thus come replace metal boundary reduce size, reduce design cost, the length of feed waveguide is 44.8mm, width is 5mm, highly it is 2mm.

Description

A double-layer waveguide slot near-field focusing array antenna based on four-corner feeding

technical field

The invention relates to a waveguide slot antenna, in particular to a double-layer waveguide slot near-field focusing array antenna based on four-corner feeding, which can be used in the fields of radio communication, near-field communication, medical detection and the like.

Background technique

An antenna array (or array antenna) is an antenna system composed of many identical individual antennas arranged in a certain order to transmit or receive radio waves. Each antenna element is connected to a single receiver or transmitter by a feedline that feeds energy to each antenna element in a specific phase relationship. The radio waves radiated by each individual antenna combine and add up, adding together (possibly by human control) to boost the power radiated in the desired direction and reduce the power radiated in other directions. Among them, the waveguide array antenna refers to an antenna that has a slit on the wide or narrow side of the waveguide and cuts off the current on the inner wall of the waveguide ([1] Song Zheng, Zhang Jianhua, Huang Zhi. Antenna and Radio Wave Propagation. Xidian University Press. 2003.7). According to the gap between the slot units and the feeding method, there are two main types of waveguide slot antenna arrays:

A resonant slot array, all slots are excited in the same phase, the maximum radiation direction is perpendicular to the antenna axis, and the waveguide terminal is usually equipped with a short-circuit piston. Resonant antennas typically have narrow bandwidth and high efficiency.

A non-resonant slotted array, the excitation signal is applied to one end of the waveguide, and the matching load is applied to the other end. Compared with resonant antennas, non-resonant antennas have a wider frequency band, but are less efficient. If the number of slot units is large enough, the energy absorbed by the load is limited, so there is not much difference in efficiency from the resonant antenna.

Chinese patent 201410744296.8 discloses a wide-band single-cavity waveguide slot resonant antenna. The design provides a rectangular waveguide wide-side longitudinal direct radiation slot antenna with good broadband, low cross-polarization characteristics, especially high antenna compression and simple structure. .

Chinese patent 201110146539.4 discloses an amplitude-phase weighted narrow-side waveguide slot array antenna. This design provides a high-gain narrow-side waveguide slot array with compact structure, simple processing, and irregular beamforming that is more suitable for spaceborne antenna applications. Shaped antenna.

However, most of these waveguide slot arrays have feed ports at the center. When the array is large in scale, it is difficult to control the element excitation to achieve the common Taylor distribution, Gaussian distribution, etc. Moreover, these antennas work in the far field, and there are few near-field focusing methods. Generally, metal is used as the isolation terminal, and copper is used as the material for isolating electromagnetic waves in most cases, which will increase the cost in some cases.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies and unconsidered points of the above-mentioned existing waveguide slot array antenna, provide the PMC boundary and PEC boundary formed equivalently inside the waveguide, reduce the size of the antenna, reduce the structural cost, and work in the near field area. It can be used in medical detection, near-field communication and other fields. The feeding method improves anti-interference and is easier to control the Taylor excitation of the array element. It is a double-layer waveguide slot near-field focusing array antenna based on four-corner feeding to achieve low sidelobe of the antenna.

The present invention consists of a feeder waveguide on the lower layer and a radiation waveguide on the upper layer; the incident wave passes through the feeder waveguide, the coupling slot, and the radiation waveguide sequentially from the feeder port, and finally radiates to the external space through the radiation slot. The waveguide adopts the standard feed waveguide to be fed from the back through the central aperture, and the four-corner feed is used instead of the traditional center feed, and the signal is extended from the center to the 4 antenna angles through the feed waveguide with 4 arms, from both ends to the middle Equal-amplitude and same-direction feeding can form a PMC boundary in the center of the feeding waveguide, thereby replacing the metal boundary to reduce size and reduce design costs. The length of the feeding waveguide is 44.8mm, the width is 5mm, and the height is 2mm;

The coupling slots are fed in the same phase. The coupling slots are opened on the upper surface of the feeding waveguide. It has the advantages of regular arrangement and suppression of the second-order beam. The number of coupling slots is 2×8; the one-dimensional Taylor distribution of the coupling slots is determined by the coupling The deflection angle of the slot is controlled, the length of the coupling slot is 3.75mm, the width is 1mm, and the thickness is 0.4mm; the distance L _c between adjacent coupling slots is 0.5λ _gf , and the distance between the terminal coupling slot and the end face of the waveguide is 0.5λ _gf , λ _gf is the wavelength of the feeding waveguide.

The radiation waveguide is placed on the upper part of the feed waveguide of the lower layer, and the coupling gap opened on the upper surface of the feed waveguide is used to feed in the same phase. The length is 42.8mm, the width is 5.2mm, and the height is 2mm; Into a PEC terminal, this equivalent terminal can replace the metal border and reduce costs.

The radiation slot adopts a waveguide slot array, the radiation slot is opened on the upper surface of the radiation waveguide, its phase is calculated from the focus position, the amplitude is Taylor distribution, the number of radiation slots is 8×8, the length of each radiation slot is 3.87mm, and the width is 1.5mm, the thickness is 0.4mm; the distance L _r between adjacent radial slits in the transverse direction is λ _g , the distance between the longitudinal direction depends on the required focus position, and the distance between the center of the four-corner radiation slit at the terminal and the upper and lower terminal surfaces of the waveguide is 0.5λ _gr , λ _gr is the wavelength of the radiation waveguide.

The working principle of the present invention is: the feeding port and the feeding waveguide adopt the Q-band standard feeding waveguide to feed in from the back through the central aperture, and the signal is extended from the center to the four antenna angles through the feeding circuit with 4 arms. In the feeding waveguide, the coupling slot adopts the excitation mode of equal amplitude and same phase. In the feeding waveguide, the distance between the centers of the coupling slots at both ends is half the wavelength of the waveguide, that is, 0.5λ _gf . In the present invention, four-corner feeding is adopted, and due to the symmetry from both ends to the center, an equivalent PMC boundary is formed in the center, which can replace the metal boundary, thereby shortening half the waveguide wavelength, reducing structural complexity, and reducing processing costs. In addition, the equivalent PMC boundary has the advantage of larger antenna bandwidth. In the radiation waveguide and radiation slot, because of the four-corner feeding method, the upper and lower symmetrical sub-arrays also have the same amplitude and phase, and the central horizontal direction of the upper and lower two sub-arrays is equivalent to form a PEC boundary, which can replace the metal boundary. . The excitation amplitude can be controlled by the deviation of the radiation slit from the central axis of each radiation waveguide, and the excitation phase can be controlled by the longitudinal deviation of the radiation slit, so as to realize focusing in the near field. These radiation slots block the surface current of the upper layer conductor of the radiation waveguide, get excited on the aperture surface of the radiation slot, radiate electromagnetic energy outward, and become an array antenna focusing in the near field. For radiating slots, the amplitudes are Taylor distributed to reduce near-field lateral sidelobe levels. Because the present invention uses a unique four-corner feeding method, since the excitation is from the periphery to the center, compared with the traditional central feeding, the control of the coupling gap and the radiation gap is simpler and more accurate, and it is easier to realize the Taylor distribution of the amplitude.

Description of drawings

FIG. 1 is a schematic diagram of the structure of a double-layer waveguide slot near-field focusing array antenna based on four-corner feeding in the present invention.

Fig. 2 is the feeding waveguide and the coupling slot on the upper surface of the feeding waveguide of the double-layer waveguide slot near-field focusing array antenna based on quadrangular feeding in the present invention.

Fig. 3 is the radiation waveguide of the double-layer waveguide slot near-field focusing array antenna and the radiation slot on the upper surface of the radiation waveguide based on four-corner feeding in the present invention.

Figure 4 shows the metal boundary used for a general feed waveguide.

Fig. 5 is the equivalent PMC boundary applied to the feeding metal waveguide in the present invention.

Figure 6 is a metal boundary used in a general antenna radiation waveguide.

Fig. 7 is a radiating metal waveguide in which the equivalent PEC boundary is applied in the present invention.

Fig. 8 is a parameter diagram of the coupling factor of the double-layer waveguide slot near-field focusing array antenna coupling slot based on four-corner feeding in the present invention.

FIG. 9 is a normalized field diagram of the double-layer waveguide slot near-field focusing array antenna based on four-corner feeding in the vertical axis transmission direction of the present invention. In Figure 9, the focus position is 50mm, and the 3dB focus depth is 38mm.

Detailed ways

Specific embodiments of the present invention will be described below in conjunction with the accompanying drawings.

The broadband single-cavity waveguide slot resonant antenna of this embodiment works in the Q-band, the working center frequency _f0 is 40.25 GHz, the lower side frequency f _L is 39.5 GHz, and the upper side frequency f _H is 41.0 GHz. The wavelength _λgf of the feeding waveguide at the center frequency is 11.2mm, and the wavelength _λgr of the radiation waveguide at the center frequency is 10.7mm.

As shown in FIG. 1 , the embodiment of the present invention has a feed port 1 , a feed waveguide 2 , a coupling slot 3 , a radiation waveguide 4 and a radiation slot 5 . The antenna works in the Q-band, and the standard feed waveguide is used to feed in from the back through the feed port. Through the feed waveguide with four arms, the coupling slot on the feed waveguide is excited. The length of the coupling slot is 3.75 mm, the width is 1 mm, and the thickness is 0.4 mm. The distance L _c between the centers of adjacent coupling slots is 0.5λ _gf , the distance between the terminal coupling slots and the end face of the waveguide is 0.5λ _gf , and λ _gf is the wavelength of the feed waveguide. The coupling slit couples the excitation into the radiation waveguide. The radiation waveguide is located at the upper end of the coupling waveguide. A radiation slit is opened on the upper surface of the radiation waveguide. The radiation slit cuts off the current on the upper surface of the radiation waveguide. The excitation is obtained at the mouth of the radiation slit and radiates energy outward to form a waveguide slit. antenna array. The radiation slot adopts array element waveguide slot array, the amplitude is Taylor distribution, the length of each radiation slot is 3.87mm, the width is 1.5mm, and the thickness is 0.4mm. The distance L _r between the lateral centers of adjacent radiation slots is λ _gr , and the distance between the longitudinal centers depends on the focus position, as shown in Figure 9, which is the normalized field strength simulation diagram in the transmission direction of the longitudinal axis when the focus position of the embodiment is 50 mm. The focus position of 50 mm determines the distance between the longitudinal centers of the radiation slits. The distance between the radiation slots at the four corners of the terminal and the end face of the waveguide terminal is 0.5λ _gr , where λ _gr is the wavelength of the radiation waveguide. Both the feed waveguide wavelength and the radiating waveguide wavelength are given above.

In the present invention, the metal boundary shown in FIG. 4 is used for the general feeder waveguide, and the equivalent PMC boundary in FIG. 5 is applied to the feeder metal waveguide in the present invention. Due to the particularity of the four-corner feed waveguide equal-amplitude and in-phase feed, the distribution of the magnetic flow lines 6 in the feed waveguide in Figure 5 shows that the magnetic force lines are perpendicular to the equivalent PMC (ideal magnetic conductor) 8, so the metal boundary 7 can be replaced by the PMC boundary , reduce processing costs and improve radiation efficiency.

In the present invention, the metal boundary shown in FIG. 6 is used for the general antenna radiation waveguide, and the equivalent PEC boundary shown in FIG. 7 is applied to the radiation metal waveguide of the present invention. Due to the symmetry of the radiation waveguide structure, the equivalent PEC (Perfect Electric Conductor) boundary 10 formed in the center of the radiation waveguide can replace the metal boundary 9, which reduces processing difficulty and saves cost.

A specific implementation manner of utilizing the present invention is as follows: when designing the feed network, the feed port and the T-shaped feed waveguide are included. In the feeding network, it is necessary to bend the T-shaped feeding waveguide by 45°, extending to the entire plane as shown in Figure 2, and open the coupling slot shown in Figure 2 on the upper surface of the feeding waveguide to form a coupling array. The design of the radiation waveguide is shown in Figure 3, and the radiation slot needs to be designed according to the given parameters and focus position. After the feeding waveguide and radiation waveguide are designed, the two are bonded. The whole structure needs to use 5 layers of etched metal plates, and all the etched metal plates are fixed and aligned with pins to be bonded together. In addition, additional screws can be added at the center and periphery of the structure for fixing to the wireless terminal. Considering the compact structure during production, if the space is limited, the radiation slot at the center of the antenna can be replaced with a screw through hole, but this will affect the overall characteristics of the antenna. In this regard, the local gap spacing around the through hole can be widened during production to distribute the through hole, so that there is no need to replace the central gap with a through hole, and the radiation can remain relatively stable.

If the electromagnetic simulation simulator ANSYS HFSS based on the finite element method is used for the simulation of the antenna, the coupling waveguide and the radiation waveguide need to be simulated separately, and the attention is as follows: (1) Adjust the offset of the single resonant radiation slot and the central axis of the single waveguide so that Its coupling factor is the same as in Figure 8. (2) After the design of a single radiation slot is completed, the phase distribution is calculated through the focal point to determine the longitudinal distance between the centers of the radiation slots, and then the radiation slots are arranged into an array. (3) The size of the coupling factor in the design of the coupling slot is controlled by the deflection angle between the coupling slot and the central axis of the waveguide.

The invention discloses the design of a double-layer waveguide slot near-field focusing array antenna based on four-corner feeding and the realization of equivalent PMC (ideal magnetic conductor) and PEC (ideal electric conductor) terminal boundary conditions based on symmetrical feeding, and relates to a Design and feeding structure of waveguide slot antenna. The waveguide slot array antenna of the present invention adopts four-corner feeding, which is different from traditional central feeding or simple one-end feeding, and is easy to realize Taylor distribution and maintain good bandwidth characteristics. The symmetrical feed structure with equal amplitude and same phase realizes the equivalent PMC terminal in the center of the feed network, and improves the adverse effect on the radiation characteristics of the antenna caused by the traditional PEC terminal on the basis of shortening the terminal position; The center of the waveguide implements an equivalent PEC terminal, which further reduces the difficulty and cost of antenna processing. The antenna focuses on the near field, has small return loss, high sidelobe suppression, high isolation, low processing difficulty and low cost in the working frequency range, and has wide application value.

Claims (9)

1. A double-layer waveguide slot near-field focusing array antenna based on quadrangular feeding is characterized in that it is made up of a feeding waveguide of the lower floor and a radiation waveguide of the upper floor; the incident wave passes through the feeding waveguide, coupling slot, The radiation waveguide finally radiates to the outer space through the radiation slot. 2. A double-layer waveguide slot near-field focusing array antenna based on four-corner feeding as claimed in claim 1, wherein the feeding port and the feeding waveguide adopt a standard feeding waveguide to feed in from the back through the central aperture, The four-corner feed is used instead of the center feed, and the signal is extended from the center to the four antenna angles through the feed waveguide with 4 arms, and the two ends are fed to the middle with equal amplitude and the same direction, and a PMC boundary can be formed in the center of the feed waveguide . 3. A double-layer waveguide slot near-field focusing array antenna based on four-corner feeding as claimed in claim 1, wherein the length of the feeding waveguide is 44.8mm, the width is 5mm, and the height is 2mm. 4. A kind of double-layer waveguide slot near-field focusing array antenna based on quadrangular feeding as claimed in claim 1, characterized in that the coupling slot is an in-phase feeding mode, the coupling slot is opened on the upper surface of the feeding waveguide, and the coupling slot The number is 2×8. 5. a kind of double-layer waveguide slot near-field focusing array antenna based on quadrangular feeding as claimed in claim 1, it is characterized in that the one-dimensional Taylor distribution of the coupling slot is controlled by the deflection angle of the coupling slot, and the length of the coupling slot is 3.75mm, width 1mm, thickness 0.4mm. 6. A kind of double-layer waveguide slot near-field focusing array antenna based on four-corner feeding as claimed in claim 1, characterized in that the distance L _c between the adjacent coupling slots is _0.5λgf , and the distance between the terminal coupling slots and the waveguide The distance between the terminal end faces is 0.5λ _gf , where λ _gf is the wavelength of the feeding waveguide. 7. A double-layer waveguide slot near-field focusing array antenna based on four-corner feeding as claimed in claim 1, wherein the radiation waveguide is placed on the upper part of the feed waveguide of the lower layer, and is coupled by the upper surface of the feed waveguide. The slot is fed in the same phase, the length is 42.8mm, the width is 5.2mm, and the height is 2mm; it can be equivalent to a PEC terminal in the horizontal direction in the center of the radiation waveguide. 8. A double-layer waveguide slot near-field focusing array antenna based on four-corner feeding as claimed in claim 1, wherein the radiation slot adopts a waveguide slot array, and the radiation slot is opened on the upper surface of the radiation waveguide, calculated by the focus position Its phase and amplitude are Taylor distributed, the number of radiation slots is 8×8, the length of each radiation slot is 3.87mm, the width is 1.5mm, and the thickness is 0.4mm. 9. A kind of double-layer waveguide slot near-field focusing array antenna based on quadrangular feed as claimed in claim 1, is characterized in that the spacing L _r between the horizontal direction of the adjacent radiation slots is λ _g , and the vertical spacing Depending on the required focusing position, the distance between the center of the radiation slot at the four corners of the terminal and the upper and lower terminal surfaces of the waveguide is 0.5λ _gr , where λ _gr is the wavelength of the radiation waveguide.