High-selectivity gain filtering type folding reflective array antenna and working method thereof

Abstract

The invention provides a high-selectivity gain filtering type folding reflective array antenna and a working method thereof. The high-selectivity gain filtering type folding reflective array antenna comprises an auxiliary reflecting surface and a main reflecting surface, the auxiliary reflecting surface comprises a first dielectric substrate and a first metal layer located on the surface of the first dielectric substrate; the main reflecting surface comprises second to fourth dielectric substrate layers which are stacked in sequence, and second to fifth metal layers which are arranged among the dielectric substrates; the main reflecting surface forms a feed source unit at the central position and a plurality of basic units arranged at the periphery of the feed source unit in an array manner through the second to fifth metal layers; the auxiliary reflecting surface and the main reflecting surface are parallel to each other, and the surface of the first dielectric substrate, far away from the first metal layer, of the auxiliary reflecting surface is opposite to the surface of the second metal layer of the main reflecting surface; an air gap exists between the auxiliary reflecting surface and the main reflecting surface; according to the invention, high gain and direction stability are ensured, and performance characteristics of passband gain flatness, out-of-band gain rapid attenuation, high frequency selectivity and the like are realized at the same time.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology, specifically relating to a high-selectivity gain-filtering folded reflective array antenna and its operating method, which can be used in radar, satellite communication and high-frequency wireless communication systems to achieve high directivity, high gain and frequency-selective radiation characteristics. Background Technology

[0002] In current microwave and millimeter-wave applications, antenna structures that combine high gain and frequency selectivity are receiving increasing attention. High gain helps improve the system's signal-to-noise ratio and communication range, while excellent frequency selectivity and out-of-band suppression characteristics help suppress spurious radiation and interference signals in non-operating frequency bands, thereby ensuring stable operation of the system in complex electromagnetic environments.

[0003] Traditional reflective array antennas are widely used in satellite communications, radar detection, imaging ranging, and space link communications due to their advantages of high gain, low profile, and ease of fabrication. However, conventional single-layer reflective array structures typically only have good reflection efficiency within a specific frequency band, have a narrow bandwidth, and offer almost no suppression of out-of-band signals, making it difficult to achieve a balance between filtering and high gain.

[0004] To improve frequency response characteristics, researchers have proposed schemes such as multilayer coupled reflector arrays and frequency selective surface (FSS) structures to achieve bandpass filtering effects. Although these multilayer structures can improve frequency selectivity to some extent, they usually lead to increased structural thickness, higher losses, and greater fabrication difficulty, while the out-of-band gain remains high, making it difficult to achieve significant frequency selectivity.

[0005] Therefore, in existing technologies, it is difficult to simultaneously achieve high out-of-band rejection, high selectivity, high gain, and compact structure. These performance trade-offs limit the further application of reflective arrays in communication and radar systems with high requirements for high frequency, high directivity, and electromagnetic compatibility.

[0006] Therefore, there is an urgent need for a highly selective gain filter folded reflective array antenna that can achieve a compact structure, flattened passband gain, and strong out-of-band suppression while maintaining the advantages of multi-layer coupling, so as to achieve excellent frequency selectivity and engineering feasibility while radiating high gain. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing reflective array antennas, such as large structural profile, insufficient out-of-band suppression, and poor frequency selectivity, by providing a high-selectivity gain-filtering folded reflective array antenna and its operating method. This antenna employs a design combining a multi-layer bandpass polarization conversion structure with a folded reflective layout. Through interlayer coupling and resonant modulation mechanisms, it achieves high gain and directional stability while maintaining flat passband gain, rapid out-of-band gain attenuation, and high frequency selectivity. The folded structure effectively reduces the profile height of the reflective system, allowing the antenna to maintain high radiation efficiency while possessing higher integration and engineering feasibility. The structure proposed in this invention has advantages such as clear principle, flexible design, compact structure, simple manufacturing process, and low cost, and has significant engineering application value and promotion potential.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A high-selectivity gain-filtering folded reflector array antenna, comprising a sub-reflector and a main reflector arranged in front and behind layers; The sub-reflective surface includes a first dielectric substrate and a first metal layer located on the surface of the first dielectric substrate; the sub-reflective surface adopts a polarization selective grid structure; The main reflective surface includes a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate layer stacked sequentially, and a second metal layer, a third metal layer, a fourth metal layer, and a fifth metal layer disposed between each dielectric substrate; the second metal layer is located on the surface of the second dielectric substrate away from the third dielectric substrate, the third metal layer is located on the surface of the third dielectric substrate away from the fourth dielectric substrate, the fourth metal layer is located on the surface of the fourth dielectric substrate close to the third dielectric substrate, and the fifth metal layer is located on the surface of the fourth dielectric substrate away from the third dielectric substrate. The main reflector is formed by a feed element located at the center through a second metal layer, a third metal layer, a fourth metal layer, and a fifth metal layer, and several basic elements arranged in an array around the feed element. The basic elements are divided into four types and are periodically distributed. Each type of basic element is composed of the corresponding basic element patterns of the second metal layer, the third metal layer, the fourth metal layer, and the fifth metal layer. The reflection phases of the four types of basic elements are 0°, 90°, 180°, and 270°, respectively. The sub-reflecting surface and the main reflecting surface are parallel to each other, and the surface of the first dielectric substrate away from the first metal layer of the sub-reflecting surface is arranged opposite to the surface of the second metal layer of the main reflecting surface; there is an air gap between the sub-reflecting surface and the main reflecting surface to provide a folding path for the propagation of electromagnetic waves between the main and sub-reflecting surfaces.

[0009] Preferably, the basic unit pattern of the second metal surface is composed of an outer square ring patch and an inner square patch, with a gap between the outer square ring patch and the inner square patch, which together form a ring-shaped gap structure.

[0010] Preferably, the basic unit pattern of the third metal surface is a rectangular patch with a U-shaped groove structure on its surface, and the basic unit pattern of the third metal surface is arranged in a one-to-one correspondence with the basic unit pattern of the second metal surface in space.

[0011] Preferably, the fourth metal surface is a continuous grounding metal layer with several slits on its surface. The continuous grounding metal layer is divided into several continuous grounding metal units according to the arrangement of the basic units. Then, the basic unit pattern of the fourth metal surface is a continuous grounding metal unit with two mutually perpendicular slits on its surface.

[0012] Preferably, the basic unit pattern of the fifth metal surface consists of two bottom resonant structures and a phase-adjusting metal connecting line; the bottom resonant structure consists of an open resonant ring and two rectangular patches connected thereto, used to achieve specific resonant characteristics; the phase-adjusting metal connecting line connects the two bottom resonant structures in a bent form through the rectangular patches, used to adjust the reflection phase and energy distribution.

[0013] Preferably, the basic unit is divided into four types based on the differences in the pattern of the basic unit of the fifth metal surface: The Type II basic unit is obtained by changing the length of the phase-adjusting metal connecting line based on the Type I basic unit; Type III and Type IV basic units are obtained by mirroring the bottom resonant structure and the phase-adjusting metal connecting line connected to it along the geometric center axis of the unit, based on Type I and Type II basic units, respectively.

[0014] Preferably, the feed unit is configured for each metal layer as follows: The feed unit corresponding region of the second metal layer includes a composite radiating patch located at the center, and six square patches symmetrically distributed around the composite radiating patch. The feed unit area corresponding to the third metal layer is an empty area without metal coverage; The feed unit area of ​​the fourth metal layer corresponds to a continuous grounded metal layer; The feed unit area of ​​the fifth metal layer includes a metal patch located at the center; The six square patches are electrically connected to the continuous grounding metal layer through the first metallized via to form a multi-point grounding structure; the metal patch is electrically connected to the continuous grounding metal layer through the first metallized via to extend the grounding plane; and the composite radiating patch is connected to the inner conductor of the feed SMA connector through the second metallized via.

[0015] Preferably, the composite radiating patch includes a main square patch with chamfered corners and T-shaped patch structures extending from the left and right sides of the main square patch, and the composite radiating patch is arranged symmetrically from left to right.

[0016] Preferably, a circular metal removal area is provided in both the continuous grounding metal layer area and the metal patch area corresponding to the second metallized via location, so as to avoid direct short circuit between the via and the ground layer.

[0017] A method for operating a high-selectivity gain-filtering folded reflector array antenna, wherein the method is implemented using any of the aforementioned high-selectivity gain-filtering folded reflector array antennas, is as follows: The main reflector radiates electromagnetic waves through the feed unit, and the polarization direction of the electromagnetic waves is consistent with the reflection polarization direction of the sub-reflector, so as to realize the reflection of electromagnetic waves through the sub-reflector. The main reflector performs bandpass polarization conversion on the reflected echo from the sub-reflector, converting the reflected echo into a polarization state orthogonal to the original polarization direction and completing phase compensation and energy focusing. The resulting directional beam is transmitted through the sub-reflector and then radiates forward.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This antenna integrates filtering and focusing functions in the main reflector, which has both bandpass polarization conversion and phase modulation capabilities, enabling both frequency-selective filtering and wavefront focusing and direction control. Compared with the traditional folded filter reflector array where the sub-reflector handles filtering and the main reflector only provides focusing, this invention significantly simplifies the system structure and achieves an integrated design of filtering and focusing functions.

[0019] (2) The antenna adopts an integrated design of feed source and array. The patch feed source structure is directly integrated in the center of the main reflector, eliminating the need to use a traditional horn antenna as the feed source. This reduces the assembly space between the feed source and the array, making the whole system more compact and lightweight, and is conducive to achieving high-precision array integration.

[0020] (3) This invention achieves a balance between strong out-of-band suppression and high in-passband reflection efficiency through a multi-layer bandpass polarization conversion structure, maintaining high gain and excellent directivity while exhibiting good frequency selectivity. The structure is simple in design, low in manufacturing cost, and easy to implement, possessing high engineering application value and promotion potential. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural schematic diagram of the present invention; Figure 2 This is a schematic diagram of the layered structure of the main reflective surface of the present invention; Figure 3 This is a schematic diagram of the basic unit structure of the main reflective surface of the present invention; Figure 4 This is a schematic diagram of the four phase response unit structures of the main reflective surface of the present invention; Figure 5 This is a schematic diagram of the arrangement of each unit type in the main reflective surface array of the present invention; Figure 6 This is a schematic diagram of the feed antenna described in this invention; Figure 7 This is the radiation pattern of the present invention at a center frequency of 10 GHz; Figure 8 This is the curve showing the axial gain of the present invention as a function of frequency.

[0022] The markings in the diagram are: 1-sub-reflective surface, 2-main reflective surface, 11-first dielectric substrate, 12-first metal layer, 21-second dielectric substrate, 22-third dielectric substrate, 23-fourth dielectric substrate, 24-second metal layer, 25-third metal layer, 26-fourth metal layer, 27-fifth metal layer, 271-bottom resonant structure, 272-phase adjustment metal connection line, 3-first metallized via, 4-second metallized via. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1-8 The technical solution of the present invention will be described in detail below.

[0024] This invention proposes a highly selective gain filter-type folded reflective array antenna, comprising a sub-reflector 1 and a main reflector 2 arranged in front and behind layers; the sub-reflector 1 adopts a polarization-selective grating structure to separate the polarization of the incident electromagnetic wave, enabling transmission of one polarization component and reflection of the other polarization component orthogonal to it, thereby achieving spatial selection of polarization direction and energy distribution; the main reflector 2 is composed of reflective array elements with reflective bandpass polarization conversion characteristics; The sub-reflective surface 1 includes a first dielectric substrate 11 and a first metal layer printed on the surface of the first dielectric substrate; The main reflective surface 2 adopts a multilayer lamination structure, which is integrally formed by lamination process of second dielectric substrate 21, third dielectric substrate 22 and fourth dielectric substrate 23, with a second metal layer 24, a third metal layer 25, a fourth metal layer 26 and a fifth metal layer 27 sequentially disposed therebetween. The second metal layer 24 is located on the surface of the second dielectric substrate 21 away from the third dielectric substrate 22, the third metal layer 25 is located on the surface of the third dielectric substrate 22 away from the fourth dielectric substrate 23, the fourth metal layer 26 is located on the surface of the fourth dielectric substrate 23 close to the third dielectric substrate 22, and the fifth metal layer 27 is located on the surface of the fourth dielectric substrate 23 away from the third dielectric substrate 22. The first dielectric substrate 11, the second dielectric substrate 21, the third dielectric substrate 22 and the fourth dielectric substrate 23 are all square and have the same size. The centers of the three are located on the same straight line, which is parallel to the z-axis. The main reflector 2 forms a feed unit (used to generate and radiate incident electromagnetic waves to excite the system) at the center through a second metal layer 24, a third metal layer 25, a fourth metal layer 26, and a fifth metal layer 27, and several basic units arranged in an array around the feed unit. The basic units are divided into four types and are periodically distributed. Each type of basic unit is composed of the corresponding basic unit patterns of the second metal layer 24, the third metal layer 25, the fourth metal layer 26, and the fifth metal layer 27. The reflection phases of the four types of basic units are 0°, 90°, 180°, and 270°, respectively. By combining different phase units, a quantized phase distribution can be formed on the reflector surface to realize a 2-bit phase-coded reflector array structure. The sub-reflector 1 and the main reflector 2 are parallel to each other, and the surface of the first dielectric substrate 11 of the sub-reflector 1, which is away from the first metal layer, is arranged opposite to the surface of the second metal layer 24 of the main reflector 2. There is an air gap between the sub-reflector 1 and the main reflector 2 to provide a folding path for the propagation of electromagnetic waves between the main and sub-reflectors 1 and to reduce the overall profile of the antenna.

[0025] The basic unit pattern of the second metal surface is composed of an outer square ring patch and an inner square patch (slotted square patch structure). There is a gap between the outer square ring patch and the inner square patch, which together form a ring gap structure. This structure is used to generate polarization conversion zeros in the low frequency band to improve filter selectivity.

[0026] The basic unit pattern of the third metal surface is a rectangular patch with a U-shaped groove structure on the surface, and the basic unit pattern of the third metal surface is arranged in a one-to-one correspondence with the basic unit pattern of the second metal surface in space; the U-shaped groove structure is used to adjust the current distribution in the high-frequency band, thereby generating a polarization conversion zero point in the high-frequency band.

[0027] The fourth metal surface is a continuous grounded metal layer with several slits on its surface. The continuous grounded metal layer is divided into several continuous grounded metal units according to the arrangement of the basic units. The basic unit pattern of the fourth metal surface is a continuous grounded metal unit with two mutually perpendicular narrow slits on its surface. An electromagnetic coupling channel is formed through the two mutually perpendicular narrow slits, so that the electric field in the upper structure can couple with the resonant structure below through the slits, thereby realizing the transfer of energy between fields.

[0028] The basic unit pattern of the fifth metal surface consists of two bottom resonant structures 271 and a phase adjustment metal connecting line 272. The bottom resonant structure 271 is composed of an open resonant ring and two rectangular patches connected to it, which are used to achieve specific resonant characteristics. The phase adjustment metal connecting line 272 connects the two bottom resonant structures 271 in a bent form through the rectangular patches, which is used to adjust the reflection phase and energy distribution.

[0029] The basic units are divided into four types based on the differences in the patterns of the fifth metal surface basic units (different geometric shapes and orientations of the phase adjustment metal connecting lines 272): The Type II basic unit is obtained by changing the length of the phase-adjusting metal connecting line 272 based on the Type I basic unit, and there is a reflection phase difference of about 90° between the two. The Type III and Type IV basic units are obtained by mirroring the bottom resonant structure 271 and the phase adjustment metal connecting line 272 connected to it along the geometric center axis of the unit, respectively, based on the Type I and Type II basic units.

[0030] like Figure 5 As shown, in this embodiment of the invention, the main reflector array 2 adopts a periodic arrangement, consisting of 20×20 basic units. The various types of units are distributed on the reflector surface according to a predetermined pattern to form a 2-bit phase-coded reflector array structure, thereby creating a quantized phase distribution on the reflector surface and achieving control over the reflected wavefront.

[0031] The feed element adopts a patch antenna structure and is located at the center of the main reflector 2 to excite the incident electromagnetic wave; the specific arrangement of each metal layer of the feed element is as follows: The feed unit corresponding region of the second metal layer 24 (the radiation patch layer used as the feed) includes a composite radiation patch located at the center, and six square patches symmetrically distributed around the composite radiation patch to obtain stable radiation characteristics and good polarization performance. The feed unit area of ​​the third metal layer 25 is an empty area without metal coverage; The feed unit area of ​​the fourth metal layer 26 is a continuous grounded metal layer; The feed unit area of ​​the fifth metal layer 27 includes a metal patch located at the center; The six square patches are electrically connected to the continuous grounding metal layer through the first metallized via 3, forming a multi-point grounding structure to improve current distribution and enhance radiation stability. The metal patch is electrically connected to the continuous grounding metal layer through the first metallized via 3 to extend the grounding plane downwards, so as to achieve a reliable welding connection with the feed SMA connector and ensure the electrical continuity and mechanical stability of the feed structure. The feed is provided by the second metallized via 4, and the composite radiating patch is connected to the inner conductor of the feed SMA connector through the second metallized via 4 to provide an excitation signal for the radiating patch.

[0032] The composite radiating patch includes a main square patch with chamfered corners, and T-shaped patch structures extending from the left and right sides of the main square patch. The composite radiating patch is symmetrically arranged from left to right. Six square patches are symmetrically distributed around the perimeter of the composite radiating patch, and each patch maintains a preset distance from the central composite radiating patch.

[0033] The continuous grounding metal layer area and the metal patch area corresponding to the location of the second metallized via 4 are provided with circular metal removal areas to avoid direct short circuit between the via and the ground layer.

[0034] Explanation of reference numerals and symbols in the attached figures: in h 1 It is the distance between the primary reflector 2 and the secondary reflector 1. t 1 represents the thickness of sub-reflective surface 1. t 2 is the thickness of the main reflecting surface 2. w g The width of the grid metal strip is selected for polarization, and g3 is the spacing between adjacent metal strips. t 21 The thickness of the second dielectric substrate 21 t 22 The thickness of the third dielectric substrate 22 t 23 The thickness of the fourth dielectric substrate 23 is given. p For a unit period, l 5 The outer length of the outer ring of the second metal surface 24. l 6 is the length of the inner side of the outer square ring. w 7 represents the annular gap width between the outer square ring and the inner square patch. l 1 represents the length of the rectangular patch on the third metal surface 25. l 7 and l 8 represents the vertical and horizontal lengths of the U-shaped groove, respectively. w8 represents the width of the U-shaped groove. d 2 represents the distance from the horizontal edge of the U-shaped groove to the outer edge of the patch. l 2 and w 2 represents the length and width of the slit in the 26 basic units of the fourth metal surface, respectively. d 1 represents the distance between the two slits. l 3 and w 3 represents the length and width of the rectangular patch in the bottom resonant structure 271, respectively. l 4 represents the side length of the outer ring of the open resonant ring in the bottom resonant structure 271. w 6 represents the distance between the inner and outer rings of the open-circuit resonator. w 5 represents the width of the gap between the openings of the open resonator ring. D The external dimensions of the feed unit are shown below. l f and w f These are the length and width of the central main patch, respectively. l cx and l cy These are the chamfer lengths of the central master patch along the x-axis and along the y-axis, respectively. l tx and l ty These are the lengths of the T-pattern along the x-axis and along the y-axis, respectively. w t It is the width of the T-pattern. l p It is the side length of the square tiles surrounding the central main tile. g 1 represents the distance between the central main tile and the surrounding square tiles. g 2 represents the distance between each square patch. D 1 and D 2 are the diameters of the first metallized via 3 and the second metallized via 4, respectively. D 3 is the diameter of the circular metal removal zone.

[0035] This invention also proposes a method for operating a high-selectivity gain-filtering folded reflector array antenna, which is implemented using any of the aforementioned high-selectivity gain-filtering folded reflector array antennas, as detailed below: The main reflector 2 radiates electromagnetic waves through the feed element (with the patch antenna at the center of the main reflector 2 as the feed source), and the polarization direction of the electromagnetic waves is consistent with the reflection polarization direction of the sub-reflector 1, so as to realize the reflection of electromagnetic waves through the sub-reflector 1. The main reflector 2 performs bandpass polarization conversion on the reflected echo of the sub-reflector 1, converting the reflected echo into a polarization state orthogonal to the original polarization direction and completing phase compensation and energy convergence. The resulting directional beam is transmitted through the sub-reflector 1 and then radiates forward.

[0036] Working principle: The high-selectivity gain-filtering folded reflective array antenna of this invention achieves bandpass polarization conversion and high-gain radiation through the synergistic effect of the sub-reflector 1 and the main reflector 2. During operation, the patch antenna located at the center of the main reflector 2 acts as a feed source to radiate electromagnetic waves, with its polarization direction aligned with the polarization grid reflection direction of the sub-reflector 1. The incident wave is first reflected back to the main reflector 2 by the sub-reflector 1. The main reflector 2 performs bandpass polarization conversion on the returned wave, converting its polarization direction to a polarization state orthogonal to the aforementioned reflected polarization, and completing phase adjustment and wavefront focusing. The converted beam is then transmitted through the sub-reflector 1 into free space for radiation, forming a directional main beam. Through two reflections and one polarization conversion process, the antenna achieves bandpass filtering, phase reconstruction, and energy convergence of the signal. The folded layout effectively extends the electromagnetic propagation path, significantly reducing the structural profile while maintaining high-gain radiation, and achieving a comprehensive performance of flat gain within the passband, strong out-of-band suppression, and high frequency selectivity.

[0037] Figure 7 The simulation of the co-polarization and cross-polarization radiation characteristics of a high-selectivity gain-filtered folded reflector array antenna at a center frequency of 10 GHz shows that it exhibits good directivity and polarization purity in both principal planes. The main lobe direction is basically consistent with the array normal direction, the sidelobe level is low, and the cross-polarization level is significantly lower than the co-polarization component, demonstrating good polarization purity. Figure 8 The simulated axial gain versus frequency curves of the high-selectivity gain-filtered folded reflector array antenna designed in this study show that the reflector array exhibits significant bandpass characteristics in the 8–12 GHz range, with a maximum gain of 25.7 dBi. The -3 dB band is 9.4–10.6 GHz, with a relative bandwidth of 12%; the -15 dB band is 9.1–10.9 GHz, and the selectivity index (defined as the ratio of the -3 dB bandwidth to the -15 dB bandwidth) is approximately 0.67, indicating that the array has steep frequency selectivity characteristics at the edge of the operating frequency band. The out-of-band rejection levels at low and high frequencies reach 40.7 dB and 25.7 dB, respectively, demonstrating excellent out-of-band rejection performance. This significantly reduces the gain in non-operating frequency bands, thereby avoiding interference from out-of-band signals to the system operation.

[0038] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-selectivity gain-filtering folded reflective array antenna, characterized in that, This includes a secondary reflector and a primary reflector arranged in two layers. The sub-reflective surface includes a first dielectric substrate and a first metal layer located on the surface of the first dielectric substrate; the sub-reflective surface adopts a polarization selective grid structure; The main reflective surface includes a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate layer stacked sequentially, and a second metal layer, a third metal layer, a fourth metal layer, and a fifth metal layer disposed between each dielectric substrate; the second metal layer is located on the surface of the second dielectric substrate away from the third dielectric substrate, the third metal layer is located on the surface of the third dielectric substrate away from the fourth dielectric substrate, the fourth metal layer is located on the surface of the fourth dielectric substrate close to the third dielectric substrate, and the fifth metal layer is located on the surface of the fourth dielectric substrate away from the third dielectric substrate. The main reflector is formed by a feed element located at the center through a second metal layer, a third metal layer, a fourth metal layer, and a fifth metal layer, and several basic elements arranged in an array around the feed element. The basic elements are divided into four types and are periodically distributed. Each type of basic element is composed of the corresponding basic element patterns of the second metal layer, the third metal layer, the fourth metal layer, and the fifth metal layer. The reflection phases of the four types of basic elements are 0°, 90°, 180°, and 270°, respectively. The sub-reflecting surface and the main reflecting surface are parallel to each other, and the surface of the first dielectric substrate away from the first metal layer of the sub-reflecting surface is arranged opposite to the surface of the second metal layer of the main reflecting surface; there is an air gap between the sub-reflecting surface and the main reflecting surface to provide a folding path for the propagation of electromagnetic waves between the main and sub-reflecting surfaces.

2. The high-selectivity gain-filtering folded reflective array antenna according to claim 1, characterized in that, The basic unit pattern of the second metal surface is composed of an outer square ring patch and an inner square patch, with a gap between the outer square ring patch and the inner square patch, which together form a ring-shaped gap structure.

3. The high-selectivity gain-filtering folded reflective array antenna according to claim 1, characterized in that, The basic unit pattern of the third metal surface is a rectangular patch with a U-shaped groove structure on the surface, and the basic unit pattern of the third metal surface is arranged in a one-to-one correspondence with the basic unit pattern of the second metal surface in space.

4. The high-selectivity gain-filtering folded reflective array antenna according to claim 1, characterized in that, The fourth metal surface is a continuous grounding metal layer with several slits on its surface. The continuous grounding metal layer is divided into several continuous grounding metal units according to the arrangement of the basic units. Then the basic unit pattern of the fourth metal surface is a continuous grounding metal unit with two mutually perpendicular slits on its surface.

5. The high-selectivity gain-filtering folded reflective array antenna according to claim 1, characterized in that, The basic unit pattern of the fifth metal surface consists of two bottom resonant structures and a phase-adjusting metal connecting line; the bottom resonant structure is composed of an open resonant ring and two rectangular patches connected to it, which is used to achieve specific resonant characteristics; the phase-adjusting metal connecting line connects the two bottom resonant structures in a bent form through the rectangular patches, which is used to adjust the reflection phase and energy distribution.

6. The high-selectivity gain-filtering folded reflective array antenna according to claim 5, characterized in that, The basic units are divided into four types based on the differences in the patterns of the fifth metal surface basic units: The Type II basic unit is obtained by changing the length of the phase-adjusting metal connecting line based on the Type I basic unit; Type III and Type IV basic units are obtained by mirroring the bottom resonant structure and the phase-adjusting metal connecting line connected to it along the geometric center axis of the unit, based on Type I and Type II basic units, respectively.

7. The high-selectivity gain-filtered folded reflective array antenna according to claim 1, characterized in that, The specific configuration of the feed unit corresponding to each metal layer is as follows: The feed unit corresponding region of the second metal layer includes a composite radiating patch located at the center, and six square patches symmetrically distributed around the composite radiating patch. The feed unit area corresponding to the third metal layer is an empty area without metal coverage; The feed unit area of ​​the fourth metal layer corresponds to a continuous grounded metal layer; The feed unit area of ​​the fifth metal layer includes a metal patch located at the center; The six square patches are electrically connected to the continuous grounding metal layer through the first metallized via to form a multi-point grounding structure; the metal patch is electrically connected to the continuous grounding metal layer through the first metallized via to extend the grounding plane; and the composite radiating patch is connected to the inner conductor of the feed SMA connector through the second metallized via.

8. The high-selectivity gain-filtering folded reflective array antenna according to claim 7, characterized in that, The composite radiation patch includes a main square patch with chamfered corners and T-shaped patch structures extending from the left and right sides of the main square patch. The composite radiation patch is arranged in a symmetrical layout.

9. The high-selectivity gain-filtered folded reflective array antenna according to claim 7, characterized in that, The continuous grounding metal layer area and the metal patch area corresponding to the second metallized via location are provided with circular metal removal areas to avoid direct short circuit between the via and the ground layer.

10. A method for operating a high-selectivity gain-filtering folded reflective array antenna, characterized in that: The method is implemented using any one of the high-selectivity gain-filtering folded reflective array antennas described in claims 1-9, as follows: The main reflector radiates electromagnetic waves through the feed unit, and the polarization direction of the electromagnetic waves is consistent with the reflection polarization direction of the sub-reflector, so as to realize the reflection of electromagnetic waves through the sub-reflector. The main reflector performs bandpass polarization conversion on the reflected echo from the sub-reflector, converting the reflected echo into a polarization state orthogonal to the original polarization direction and completing phase compensation and energy focusing. The resulting directional beam is transmitted through the sub-reflector and then radiates forward.

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