Single-feed dual-frequency hybrid-circularly polarized fabry-perot resonant cavity antenna

Abstract

The application belongs to the field of microwave and radio frequency technology, and specifically discloses a single-feed dual-frequency different circular polarization Fabry-Perot resonant cavity antenna. The antenna comprises a metasurface array layer and a feed structure layer. The feed structure layer is used for exciting and realizing impedance matching of Ku and Ka working frequency bands through a single antenna feed point, and providing electromagnetic energy for the antenna. The metasurface array layer is used for converting the electromagnetic energy provided by the feed structure layer into different circularly polarized radiation waves. The application can improve the performance of a satellite-ground integrated communication antenna and reduce the system complexity.

Description

Technical Field

[0001] This application belongs to the field of microwave and radio frequency technology, specifically relating to a single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna. Background Technology

[0002] Satellite communication systems are widely used due to their advantages of large communication capacity, good signal transmission quality, and less susceptibility to geographical conditions and environmental factors. Meanwhile, terrestrial communication systems are booming due to their stable transmission quality at high bit rates, but are constrained by geographical conditions. Using low- and medium-Earth orbit satellites as a supplement to terrestrial mobile communication systems can achieve all-weather, seamless communication coverage, meeting the network demands for lower latency and greater capacity. Therefore, "satellite-terrestrial converged communication" is considered a key development direction for future mobile communications. Satellite communication typically uses the Ku, K, and Ka bands as its communication frequency bands.

[0003] Currently, most existing dual-band Fabry-Perot resonator antennas are either linearly polarized or circularly polarized with a narrow axial ratio bandwidth. These two types of antennas are difficult to directly apply to space-ground integrated communication systems because: firstly, satellite signals undergo Faraday rotation when traversing the ionosphere, causing a deflection of the polarization direction of linearly polarized waves, resulting in severe polarization mismatch and signal attenuation; secondly, attitude changes of mobile terminals in complex environments also degrade the performance of linearly polarized antennas. While circularly polarized waves can overcome these problems, their narrow axial ratio bandwidth makes it impossible to maintain stable circular polarization characteristics (i.e., axial ratio <3dB) across the entire wideband required for satellite communication (such as the K / Ka band). Therefore, they cannot meet the wideband, high-reliability communication requirements of space-ground integrated systems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this application is to provide a single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna. This application improves the performance of satellite-to-ground integrated communication antennas and reduces system complexity through a single-fed structure and chiral metasurface design.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna is disclosed. The antenna comprises a metasurface array layer and a feeding structure layer, wherein the feeding structure layer is used to excite and achieve impedance matching of the Ku and Ka operating frequency bands through a single antenna feed point, and to provide electromagnetic energy to the antenna; the metasurface array layer is used to convert the electromagnetic energy provided by the feeding structure layer into hetero-circularly polarized radiated waves.

[0007] Optionally, the spacing between the metasurface array layer and the feed structure layer is 15.5 mm.

[0008] Optionally, the power supply structure layer includes: a first dielectric substrate layer and a second dielectric substrate layer, which are bonded together by a metal base plate. The first dielectric substrate layer has a parasitic patch on the side facing away from the metal base plate and a square patch on the side facing the metal base plate. The second dielectric substrate layer has a microstrip feed line on the side facing away from the metal base plate, and the microstrip feed line is externally connected to an SMA power supply connector.

[0009] Optionally, a power supply gap is etched at the middle position of the metal base plate.

[0010] Optionally, the metasurface array layer includes: a stacked third dielectric substrate layer and a fourth dielectric substrate layer, wherein a plurality of first unit structures are disposed on the side of the third dielectric substrate layer facing away from the fourth dielectric substrate layer, and a plurality of second unit structures symmetrical to the plurality of first unit structures are disposed on the side of the third dielectric substrate layer facing away from the fourth dielectric substrate layer; a plurality of third unit structures symmetrical to the plurality of second unit structures are disposed on the side of the fourth dielectric substrate layer facing away from the third dielectric substrate layer; the plurality of first unit structures, the plurality of second unit structures and the plurality of third unit structures constitute a periodically arranged metasurface radiating unit structure.

[0011] Optionally, the third unit structure and the metal base plate constitute a Fabry-Perot resonant cavity.

[0012] Compared with the prior art, the beneficial effects of this application are as follows:

[0013] This application integrates a metasurface array structure and a feeding structure. The metasurface array consists of 17×17 metasurface elements, comprising two dielectric substrates and metal patches printed on the front and back sides of the substrates. The dual-band feeding structure includes the metal patches, their parasitic patches, microstrip feed lines, and slot structures. This application achieves dual-band circular polarization of the antenna through chiral design of the metasurface elements. The slots in the bottom layer of the metasurface elements ensure polarization purity under multiple reflections, achieving a wide axial ratio bandwidth. The addition of parasitic patches to the feeding structure expands the impedance bandwidth, simplifying the feeding structure to a single feed. The lower surface of the element array and the metal substrate of the feeding structure form a Fabry-Perot resonant cavity, improving the gain of the dual-band antenna. The lower slit and middle double-opening ring structure of the metasurface elements serve as the electromagnetic wave receiving structure, while the upper double-opening ring structure serves as the radiation structure, ensuring that the transmitted wave does not deflect under large-angle electromagnetic wave incidence. The antennas designed in this application operate in the K and Ka bands, respectively, with -10dB impedance bandwidths of 18.5GHz~20.0GHz and 28.3GHz~29.5GHz, respectively. The maximum gains within the operating frequency bands are 16.7dBi and 19dBi, respectively. The axial ratio of the antennas within the impedance bandwidths at both low and high frequencies is less than 3dB, and they are left-handed and right-handed circularly polarized, respectively. Attached Figure Description

[0014] Figure 1 A side view of a single-fed dual-frequency hetero-circularly polarized Fabry-Perot antenna provided for one embodiment of this application;

[0015] Figure 2 for Figure 1 Top view of the central feeder structure layer;

[0016] Figure 3 for Figure 1 A schematic diagram of the surface array layer of the Chinese supercomputer;

[0017] Figure 4 A schematic diagram of etching power supply gaps on a metal substrate;

[0018] Figure 5 This is a top view of the structure of the metasurface array layer;

[0019] Figure 6 A bottom view of the structure of the metasurface array layer;

[0020] Figure 7 Simulation curves of the dual-band -10dB impedance bandwidth of the antenna;

[0021] Figure 8 The simulation curves show the gain and axial ratio of the dual-band antenna as a function of frequency.

[0022] Figure 9 The simulated radiation pattern of the common-aperture antenna at 19.25 GHz;

[0023] Figure 10 The simulated radiation pattern of the common-aperture antenna at 28.9 GHz;

[0024] Figure 11 A schematic diagram of the metasurface unit design process;

[0025] Figure 12 This is a schematic diagram of the simulation results for the metasurface unit.

[0026] The annotations in the attached figures are explained as follows:

[0027] 1. First dielectric substrate layer; 2. Second dielectric substrate layer; 3. Metal base plate; 4. Parasitic patch; 5. Square patch; 6. Microstrip feed line; 7. Feed gap; 8. Third dielectric substrate layer; 9. Fourth dielectric substrate layer; 10. First unit structure; 11. Second unit structure; 12. Third unit structure. Detailed Implementation

[0028] Specific embodiments of this application will now be described in detail with reference to the accompanying drawings. While specific embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0029] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0030] To facilitate understanding of the embodiments of this application, the following will provide further explanation and description with reference to the accompanying drawings and specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of this application.

[0031] Figure 1 A side view of a single-fed dual-frequency hetero-circularly polarized Fabry-Perot antenna provided as an embodiment of this application; as shown Figure 1 As shown, the antenna includes a metasurface array layer and a feed structure layer, which are fixed together by connecting posts. The feed structure layer is used to excite the antenna to achieve impedance matching between the K-band and Ka-band through a single antenna feed point and to provide electromagnetic energy. The metasurface array layer is used to receive and modulate the electromagnetic energy from the feed structure layer, reconstructing it into a radiated wave with heterocircular polarization characteristics that radiates in space.

[0032] In another exemplary embodiment, the spacing between the metasurface array layer and the feed structure layer is 15.5 mm.

[0033] In this embodiment, the spacing between the metasurface array layer and the feed structure layer is set to 15.5 mm, primarily based on the optimized design of the Fabry-Perot resonator's resonance conditions. This spacing is proportional to the wavelength of the antenna's operating frequency band (K / Ka band), ensuring that the electromagnetic waves radiated from the metasurface are superimposed in phase with the reflected waves from the metal substrate within the cavity, thereby enhancing antenna gain and improving radiation directivity. Furthermore, it should be noted that experimental testing shows that if the spacing is greater than 15.5 mm, it leads to phase mismatch from multiple reflected waves within the cavity, causing resonant frequency shift, gain reduction, axial ratio deterioration, and even radiation pattern splitting or increased sidelobe levels. Conversely, if the spacing is less than 15.5 mm, insufficient cavity height weakens the interaction between reflected and radiated waves, resulting in poor impedance matching, narrowed bandwidth, and reduced radiation efficiency. It also excites unwanted higher-order modes, affecting the antenna's circular polarization purity and radiation stability. Therefore, a 15.5 mm spacing is a key structural parameter ensuring efficient radiation, stable circular polarization, and good impedance matching in both frequency bands.

[0034] In another exemplary embodiment, please continue to refer to Figure 1 and Figure 2 The power supply structure layer includes: a first dielectric substrate layer 1 and a second dielectric substrate layer 2, which are bonded together by a metal base plate 3. A parasitic patch 4 is provided on the side of the first dielectric substrate layer 1 facing away from the metal base plate 3, and a square patch 5 is provided on the side facing the metal base plate 3. A microstrip feed line 6 is provided on the side of the second dielectric substrate layer 2 facing away from the metal base plate 3, and the microstrip feed line 6 is externally connected to an SMA power supply connector.

[0035] In this embodiment, the working principle of the feeding structure layer is described as follows: A microstrip feed line located on the lower surface of the second dielectric substrate layer introduces an RF signal through an external SMA feed connector. This signal is electromagnetically coupled through a metal base plate located between the first and second dielectric substrate layers to excite the square patch, thereby exciting the antenna's main resonant mode in the K-band (low frequency). Furthermore, this signal excites the parasitic patch to generate a Ka-band (high frequency) resonance. The square patch is mainly responsible for controlling the impedance and resonant frequency in the low-frequency band, while the parasitic patch is mainly responsible for expanding and optimizing the impedance bandwidth and matching characteristics in the high-frequency band. The metal base plate not only serves as a ground reference surface and structural support but also participates in the interlayer electromagnetic coupling and energy transfer between the first and second dielectric substrate layers. Ultimately, this composite structure, through single-point feeding, achieves simultaneous excitation and good impedance matching of the two relatively far-separated operating frequency bands, K and Ka, and efficiently couples electromagnetic energy to the metasurface array layer.

[0036] First, the parasitic patch alters the current path and distribution on the main patch surface. Current that was originally concentrated in a specific area of ​​the main patch will partially flow to the parasitic patch, reducing current density concentration. This lowers the equivalent series resistance, allowing impedance matching to be maintained over a wider frequency range and reducing reflection losses. Second, the parasitic patch can be considered a "passive load." By adjusting its size, shape, spacing, and position relative to the main patch, the frequency and quality factor (Q value) of new resonant modes can be flexibly adjusted. Low-Q resonant modes inherently have a wider bandwidth; when combined with the main patch, they can further broaden the overall impedance bandwidth.

[0037] Furthermore, it is important to emphasize that the relative position and spatial arrangement of the square patch and parasitic patch in the feed structure layer are decisive factors for the stable dual-band operation of this antenna. The square patch, as the main radiator in the low-frequency (K-band) band, directly determines the coupling strength and resonant frequency with the feed line and metal substrate. The parasitic patch, as the excitation and matching unit in the high-frequency (Ka-band) band, determines the excitation efficiency and impedance matching state of the high-frequency resonant mode through its offset distance and alignment accuracy relative to the square patch. Together, they constitute a precise dual-band coupled resonant system. Any offset or misalignment of their predetermined relative positions will severely disrupt the electromagnetic balance of the coupled system, potentially leading to significant frequency deviation or splitting of the dual-band resonant point, severe deterioration of impedance matching (increased return loss), decreased isolation between the two bands, or even complete detuning of one band, thereby causing the antenna's wireless performance (including impedance bandwidth, radiation efficiency, and gain) in the target frequency band to fail. Therefore, this structure requires strict process tolerance control during manufacturing and assembly to ensure that its electrical performance matches the design expectations.

[0038] In another exemplary embodiment, such as Figure 4 As shown, a power supply gap 7 is etched in the middle of the metal base plate 3.

[0039] In this embodiment, the feed slot serves to achieve efficient electromagnetic energy coupling and mode conversion between the feed structure layer and the metasurface array layer. First, as a non-contact coupling window, the slot can directionally couple the quasi-TEM mode electromagnetic field energy of the lower microstrip feed line to the upper dielectric space, thereby exciting the square patch and parasitic patch. Second, the slot can also suppress surface waves and reduce edge diffraction, which helps to improve the antenna radiation efficiency and front-to-back ratio.

[0040] Furthermore, it should be noted that placing the feed slot in the center of the metal substrate is based on the following two considerations: First, symmetry considerations: the central position ensures optimal symmetry of the feed excitation in the horizontal plane, which is conducive to exciting a regular and stable electromagnetic field distribution, providing the upper metasurface array with an incident wave with a clear phase center; second, maximizing coupling efficiency: the central position allows the slot to be directly aligned with the central region of the upper square patch, achieving the strongest near-field coupling and ensuring that energy is uniformly and efficiently transferred to the entire patch structure, thereby guaranteeing the stability and consistency of dual-band operating performance. It is important to note that if the feed slot deviates from the center of the metal substrate, it may compromise the overall performance of the antenna. First, asymmetric excitation will cause distortion of the current distribution on the upper square patch and parasitic patches, which may excite undesirable higher-order modes, distorting the antenna's radiation pattern, causing the main beam to skew, increasing the sidelobe level, and potentially deteriorating cross-polarization performance. Secondly, off-center placement leads to reduced and uneven coupling efficiency. The coupling strength between the slot and the patch weakens and becomes unevenly distributed, resulting in excessive energy in some areas and insufficient excitation in others. This not only reduces the overall radiation efficiency of the antenna but also disrupts the original impedance matching balance between the K and Ka bands, causing a significant deterioration in return loss in one or two bands, narrowing or even mismatching the impedance bandwidth. Furthermore, off-center placement may exacerbate surface wave excitation and propagation, increasing energy loss and potentially inducing parasitic coupling with the antenna structure edges or other parts, introducing additional resonance or interference, making the antenna's operating characteristics complex and unpredictable. Therefore, centering the feed slot in the metal substrate is a crucial structural constraint to ensure the antenna described in this application achieves the expected dual-band, high-performance radiation characteristics.

[0041] In another exemplary embodiment, please continue to refer to Figure 1 , Figure 3 , Figure 5 and Figure 6 The metasurface array layer includes a stacked third dielectric substrate layer 8 and a fourth dielectric substrate layer 9. The third dielectric substrate layer 8 has a plurality of first unit structures 10 disposed on the side facing away from the fourth dielectric substrate layer 9, and a plurality of second unit structures 11 symmetrical to the plurality of first unit structures 10 disposed on the side facing the fourth dielectric substrate layer 9. The fourth dielectric substrate layer 9 has a plurality of third unit structures 12 symmetrical to the plurality of second unit structures 11 disposed on the side facing away from the third dielectric substrate layer 8. The plurality of first unit structures 10, the plurality of second unit structures 11, and the plurality of third unit structures 12 constitute a periodically arranged metasurface radiating unit structure.

[0042] In this embodiment, the metasurface array layer is composed of periodically arranged metasurface radiating units. Each radiating unit works collaboratively through a three-layer cascaded resonant structure (i.e., the first, second, and third unit structures) to achieve precise control of the polarization and phase of the incident electromagnetic wave. The working principle of this metasurface array layer is as follows: the linearly polarized electromagnetic wave from the feed structure layer first excites the third unit structure, which acts as a primary resonator to perform preliminary phase modulation and energy harvesting of the incident wave; subsequently, the electromagnetic wave couples to the second unit structure, which further adjusts the wavefront distribution and forms a coupled resonance with the first unit structure, playing the role of impedance matching and polarization pre-conversion; finally, the energy is transferred to the first unit structure, which acts as the main radiating surface and efficiently radiates the accumulated electromagnetic energy into free space in the form of heterocircularly polarized waves through its specific geometric arrangement (such as chiral double rings). The three unit structures are symmetrically stacked to form a multi-resonant coupling system, which not only expands the axial ratio bandwidth of the antenna, but also generates stable circularly polarized waves with opposite rotation directions (i.e., heterocircular polarization) with an axial ratio of less than 3dB in the K-band and Ka-band respectively.

[0043] In another exemplary embodiment, the third unit structure 12 and the metal base plate 3 constitute a Fabry-Perot resonant cavity.

[0044] In this embodiment, the third unit structure and the metal base plate constitute a Fabry-Perot resonant cavity. Its function is to utilize the multiple reflections and coherent superposition effects of the resonant cavity to perform phase modulation and energy focusing on the electromagnetic waves radiated from the metasurface units. Specifically, the mechanism of this resonant cavity is as follows: Electromagnetic waves radiated downwards from the metasurface radiating units (especially the third unit structure) are reflected back into the cavity after encountering the metal base plate, where they undergo multiple reflections and gradual superposition with subsequently radiated waves. By precisely controlling the height of the resonant cavity (i.e., the distance between the metasurface array layer and the metal base plate), these reflected waves can achieve in-phase superposition at the upward radiation exit (i.e., the metasurface layer), thereby concentrating energy in the main radiation direction.

[0045] Figure 7 The image shows the simulation results of the -10dB impedance bandwidth of a single-fed, dual-frequency, circularly polarized Fabry-Perot antenna. Figure 7 As shown, the horizontal axis of the curve represents frequency (GHz), and the vertical axis represents return loss (dB). The curve reveals that the antenna exhibits clear dual-band operating characteristics. The first -10dB impedance bandwidth covers approximately 18GHz to 20GHz, with return loss approaching -5dB in the 22GHz to 27GHz range. The second -10dB impedance bandwidth covers approximately 29GHz to 31GHz. This figure demonstrates the antenna's good impedance matching performance in both frequencies, meeting design expectations.

[0046] Figure 8The simulation results of the gain and axial ratio of a single-fed, dual-frequency, hetero-circularly polarized Fabry-Perot antenna as a function of frequency within its dual-frequency operating range are shown in the following figures: Figure 8 As shown, the horizontal axis of the curve represents frequency (GHz), and the vertical axis corresponds to axial ratio (dB) and gain (dBic). The curve reveals that the antenna gain is generally greater than 10dBic in the 18GHz to 20GHz band, and remains stable above 12dBic in the 28GHz to 30GHz band. Meanwhile, the axial ratio curve is mainly distributed in the -10dB to 15dB range, and the axial ratio in both the 18GHz to 20GHz and 28GHz to 30GHz operating frequency bands is below 3dB, indicating that the antenna possesses good circular polarization characteristics at these frequencies, which is highly consistent with the design goal of dual-band operation.

[0047] Figure 9 The simulated radiation pattern of the common-aperture antenna at 19.25 GHz is shown below. Figure 9 As shown in the figure, the horizontal axis represents the scanning angle (°), covering a range from -180° to 180°, and the vertical axis represents the gain (dBic). The curves in the figure show that the antenna achieves its highest gain at 0° (normal direction), with a peak value of approximately 16dBic, indicating that the main beam radiates along the antenna's normal direction. When deviating from the normal direction, the gain drops rapidly, with significant troughs appearing near -150° and 150°, and the lowest gain approaching -20dBic. Overall, it exhibits typical directional radiation characteristics, with the main lobe concentrated in the range of -15° to 15°, and the side lobes and back lobes having relatively low gains, indicating that the antenna possesses good directional radiation capability at the 19.25GHz frequency point.

[0048] Figure 10 The simulated radiation pattern of the common-aperture antenna at 28.9 GHz is shown below. Figure 10 As shown in the figure, the horizontal axis represents the scanning angle (°), covering a range from -180° to 180°, and the vertical axis represents the gain (dBic). The curves in the figure show that the antenna achieves its highest gain at 0° (normal direction), with a peak value of approximately 19dBic, which is the main beam radiation direction at this frequency. When deviating from the normal direction, the gain drops rapidly, showing a significant trough near 100°, with the lowest gain approaching -30dBic. Overall, it exhibits typical directional radiation characteristics, with the main lobe concentrated in the range of -15° to 15°, and the side lobes and back lobes having relatively low gains. This indicates that the antenna possesses good directional radiation capability at the 28.9GHz frequency, and the main lobe gain at this frequency is slightly higher than its performance at the 19.25GHz frequency.

[0049] Figure 11This diagram illustrates the design process of metasurface units, showcasing the structural evolution from unit 1 to unit 4. Unit 1 is a single-layer, large-sized square nested metal ring structure; unit 2 is a single-layer, small-sized square nested metal ring structure; unit 3 is a double-layer structure formed by perpendicularly stacking units 1 and 2; and unit 4 is an optimized double-layer nested metal ring structure based on unit 3. By adjusting the size and stacking method of the metal rings, precise control of the electromagnetic response is gradually achieved, enhancing the unit's transmission efficiency and circular polarization conversion performance.

[0050] Figure 12 The simulation results of the above-mentioned unit structure evolution process are presented, and the corresponding electromagnetic characteristics are shown in Table 1:

[0051] Table 1 Electromagnetic properties

[0052]

[0053] As shown in Table 1, the metasurface unit evolved from the single-layer large-size nested metal ring structure of unit 1 to the optimized double-layer nested metal ring structure of unit 4, gradually realizing the improvement of transmission efficiency and the optimization of circular polarization performance: unit 1 has a good axial ratio but weak transmission near 18.5 GHz, unit 2 has enhanced transmission effect at dual frequencies but no polarization conversion, unit 3 has both dual-frequency transmission and preliminary axial ratio characteristics through vertical stacking, and the finally optimized unit 4 exhibits high transmission efficiency and stable circular polarization performance near 18.5 GHz and 29 GHz, meeting the antenna's dual-frequency hetero-circular polarization design requirements in the K / Ka band.

[0054] The above embodiments are only for illustrating the technical concept and features of this application, and are intended to enable those skilled in the art to understand the content of this application and implement it accordingly. They should not be construed as limiting the scope of protection of this application. All equivalent changes or modifications made in accordance with the spirit and essence of this application should be included within the scope of protection of this application.

Claims

1. A single-fed, dual-frequency, hetero-circularly polarized Fabry-Perot resonant cavity antenna, characterized in that, The antenna includes: The metasurface array layer and the feed structure layer, wherein the feed structure layer is used to excite and achieve impedance matching of the Ku and Ka operating frequency bands through a single antenna feed point, and to provide electromagnetic energy to the antenna; The metasurface array layer is used to convert the electromagnetic energy provided by the feed structure layer into circularly polarized radiation waves. The metasurface array layer includes: The stacked third and fourth dielectric substrate layers, wherein, A plurality of first unit structures are provided on the side of the third dielectric substrate layer facing away from the fourth dielectric substrate layer, and a plurality of second unit structures symmetrical to the plurality of first unit structures are provided on the side facing the fourth dielectric substrate layer. A plurality of third unit structures symmetrical to the plurality of second unit structures are provided on the side of the fourth dielectric substrate layer facing away from the third dielectric substrate layer; Multiple first-unit structures, multiple second-unit structures, and multiple third-unit structures constitute a periodically arranged metasurface radiative unit structure; The first unit structure is a single-layer, large-size square nested metal ring structure, and the second unit structure is a single-layer, small-size square nested metal ring structure. The first unit structure and the second unit structure form a double-layer nested metal ring structure.

2. The single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna according to claim 1, characterized in that, The spacing between the metasurface array layer and the feed structure layer is 15.5 mm.

3. The single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna according to claim 1, characterized in that, The power supply structure layer includes: A first dielectric substrate layer and a second dielectric substrate layer are bonded together by a metal substrate. A parasitic patch is provided on the side of the first dielectric substrate layer facing away from the metal base plate, and a square patch is provided on the side facing the metal base plate. A microstrip feed line is provided on the side of the second dielectric substrate layer facing away from the metal base plate, and the microstrip feed line is externally connected to an SMA power supply connector.

4. The single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna according to claim 3, characterized in that, A power supply gap is etched in the middle of the metal base plate.

5. The single-fed dual-frequency hetero-circularly polarized Fabry-Perot resonant cavity antenna according to claim 3 or 4, characterized in that, The third unit structure and the metal base plate together form a Fabry-Perot resonant cavity.

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