Ultra-wideband rcs reduction circularly polarized antenna based on polarization conversion metasurface

Abstract

The application belongs to the technical field of electronic equipment, and relates to a divergence integrated antenna technology, and provides an ultra-wideband RCS reduction circularly polarized antenna based on a polarization conversion metasurface, which comprises four radiation subarrays, four sixteenth-division feed networks, one four-division phase rotation feed network and one radio frequency coaxial connector, the four radiation subarrays are arranged in a 2*2 chessboard array, the input end of the four-division phase rotation feed network is connected with the radio frequency coaxial connector, the four output ends of the four-division phase rotation feed network are connected with the sixteenth-division feed networks one by one, the sixteenth-division feed networks are connected with the radiation subarrays one by one and feed power, and the feeding phases of the four radiation subarrays are sequentially different by 90 DEG in the counterclockwise direction. Based on this, the circularly polarized antenna provided by the application realizes high-gain circularly polarized radiation and reception in the working frequency band, has the RCS reduction performance, and has good angle stability of RCS reduction in the working frequency band.

Description

Technical Field

[0001] This invention belongs to the field of electronic equipment technology and relates to radiative integrated antenna technology. Specifically, it provides an ultra-wideband RCS-reduced circularly polarized antenna based on a polarization conversion metasurface. Background Technology

[0002] Compared to traditional antennas, radiative-dispersion integrated antennas achieve integrated control of radiation and scattering through the fusion of metasurfaces and antennas. Based on the current development of antenna technology, polarization-conversion surfaces and artificial magnetic conductors are often used in radiative-dispersion integrated low-scatter antennas. The integration of these two with antenna feeding technology can achieve polarization conversion and radiation functions on the same structure, eliminating the need for lumped components, enhancing the utilization of limited space and device lifespan, and exhibiting low profile and low cost characteristics, making it easy to integrate with radar systems. Depending on the implementation method, various types of radiative-dispersion integrated antennas can be realized using the eigenmodes of metasurface arrays and the resonant modes of metasurface elements.

[0003] To meet the increasingly complex application requirements, divergence-integrated antennas are developing towards wider passband and wider out-of-band radar cross section reduction. For example, as shown in the paper "Circularly Polarized Polarization Conversion Metasurface-Inspired Antenna Array With Low RCS Over a Wide Band", Pengfeiwang et al. disclosed a circularly polarized antenna array excited by a polarization conversion surface with wideband RCS reduction. The polarization conversion surface unit is directly used as the antenna radiator without increasing the structural complexity, while reducing the in-band and out-of-band radar cross sections. The use of metasurfaces can make the structure have both in-band radiation and out-of-band RCS reduction characteristics, thus forming a divergence-integrated structure with advantages such as low profile, low cost, easy processing, and excellent performance. However, since this antenna is a single-layer structure, the bandwidth of out-of-band RCS reduction is relatively narrow, which limits its functional applications. For example, as shown in the paper "Ultra-Wideband Low-RCS Circularly Polarized Antennas Realized by Bilayer PolarizationConversion Metasurfaces and Novel Feeding Networks", Xi Gao et al. disclosed an ultra-wideband low-RCS circularly polarized antenna realized by a bilayer polarization conversion metasurface and a novel feeding network. Through four sequentially fed slots and a phase-adjusting surface, together with the polarization conversion surface, they achieved a low-frequency wideband circularly polarized passband and ultra-wideband RCS reduction performance in the high-frequency band. The phase-adjusting surface can effectively adjust the ultra-wideband polarization conversion performance, and the use of the polarization conversion surface can make the antenna have a low profile and wideband radiation performance formed by the characteristic modes generated by the polarization conversion surface array. However, since the radiation performance is formed by characteristic modes, the antenna cannot effectively utilize the antenna aperture, which leads to limited gain, and it cannot achieve RCS reduction in the low-frequency part, thus limiting its functional applications. In addition, the angular stability of RCS reduction within the operating frequency band is poor. Summary of the Invention

[0004] The purpose of this invention is to provide an ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface, which can achieve high-gain circularly polarized radiation and reception in the operating frequency band, while having RCS reduction performance and good angular stability of RCS reduction in the operating frequency band.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface includes: four radiating subarrays, four sixteen-part feed networks, one four-part phase-rotating feed network, and one radio frequency coaxial connector. The four radiating subarrays are arranged in a 2×2 checkerboard pattern. The sixteen-part feed network, the four-part phase-rotating feed network, and the radio frequency coaxial connector together constitute the feed structure. The input end of the four-part phase-rotating feed network is connected to the radio frequency coaxial connector. The four output ends of the four-part phase-rotating feed network are connected one-to-one with the sixteen-part feed network. The sixteen-part feed network is connected one-to-one with the radiating subarrays and feeds them. The feed phases of the four radiating subarrays differ by 90° sequentially in a counterclockwise direction.

[0007] Furthermore, the radiating subarray consists of 16 polarization conversion radiating units arranged in a 4×4 matrix. Each polarization conversion radiating unit includes: a first dielectric layer, a metal ground plane, a lamination layer, a second dielectric layer, a first metal layer, a third dielectric layer, a second metal layer, a feed microstrip line, and a conductive metal pillar. The feed microstrip line is disposed on the lower surface of the first dielectric layer, the metal ground plane is disposed on the upper surface of the first dielectric layer, the second dielectric layer is laminated onto the upper surface of the metal ground plane via the lamination layer, the first metal layer is disposed between the second and third dielectric layers, and the second metal layer is disposed on the upper surface of the third dielectric layer. The conductive metal pillar penetrates the first dielectric layer, the metal ground plane, the lamination layer, and the second dielectric layer, with its bottom end connected to the feed microstrip line and its top end connected to the first metal layer. The metal ground plane and the lamination layer have circular holes corresponding to the conductive metal pillars for isolation. The feed microstrip line is connected to the output end of a sixteen-part feed network, and the polarization conversion radiating unit is fed through the feed structure.

[0008] Furthermore, the first metal layer adopts a patterned structure, including: one I-shaped patch, two isosceles right-angled triangle patches, and two subwavelength bends; wherein, the I-shaped patch is arranged along the diagonal of the upper surface of the second dielectric layer, and the two isosceles right-angled triangle patches are arranged at diagonal positions along the same diagonal; the I-shaped patch and the isosceles right-angled triangle patches are simultaneously provided with channels to accommodate the bends, and the two ends of the bends connect the I-shaped patch and the isosceles right-angled triangle patches, and the bends are also arranged along the same diagonal.

[0009] Furthermore, the second metal layer employs a rectangular coupling patch, which is located at the center of the upper surface of the third dielectric layer.

[0010] Furthermore, the four radial subarrays adopt the same structure and are arranged at intervals after being rotated by 0°, 90°, 180° and 270° respectively, forming a 2×2 chessboard array arrangement.

[0011] Furthermore, the sixteen-way equal-amplitude power divider network includes 15 one-to-two power dividers, which are connected by a reference microstrip line to achieve 16 equal-amplitude and in-phase outputs.

[0012] Furthermore, the four-phase rotating feed network includes: three 1-to-2 power dividers, one 180° phase-shifted microstrip line, and two 90° phase-shifted microstrip lines. The RF input signal is split into two paths after passing through the first power divider. One path is connected to the second power divider via a reference connection microstrip line, and the other path is connected to the third power divider via the 180° phase-shifted microstrip line. The second and third power dividers have direct outputs from one output terminal and outputs from the other terminal via the 90° phase-shifted microstrip line, so that the phases of the four output ports of the four-phase rotating feed network are successively 90° apart in a counterclockwise direction.

[0013] Furthermore, in the four-phase rotating power supply network, a resistor is set between the two output terminals of each 1-to-2 power divider for port isolation.

[0014] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0015] 1. The ultra-wideband RCS reduced circular polarization antenna of this invention can perform high-gain circular polarization radiation and reception within the band, with a return loss greater than 10dB, an impedance bandwidth of 31.78% (12.25GHz~16.88GHz), a 3dB gain bandwidth of 13.4-17GHz, a 3dB axial ratio bandwidth of 28.57% (13.2GHz~17.6GHz), and an in-band peak gain of 14.22dBi, making it suitable for most high-gain transceiver scenarios;

[0016] 2. This invention can achieve RCS reduction performance in ultra-wideband, with a radar cross section reduction frequency range of 110.2% (5.5GHz~19GHz) and a reduction efficiency of more than 6dB. It can be applied to most electromagnetic compatibility and stealth radar scenarios.

[0017] 3. The ultra-wideband RCS-reduced circularly polarized antenna of the present invention has good angular stability and has a frequency band RCS reduction of more than 8dB in the full band and near band within a 45° elevation angle range;

[0018] 4. The ultra-wideband RCS reduced circularly polarized antenna of the present invention adopts three layers of dielectric material and four layers of metal structure, which can be realized by stacking PCB boards, resulting in low cost, no need for lumped components in the unit, and simple processing; in addition, the overall profile is low, and the size of the radiating unit is about a quarter wavelength. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the structure of the ultra-wideband RCS reduced circular polarized antenna based on the polarization conversion metasurface in this invention. In the diagram, 1 is the radiating subarray, 2 is the sixteen-part feed network, 3 is the four-part phase rotation feed network, and 4 is the radio frequency coaxial connector.

[0020] Figure 2 This is a schematic diagram of the structure of the radiating subarray in this invention.

[0021] Figure 3 This is a schematic diagram of the polarization conversion radiation unit in this invention, wherein 1-1 is the first dielectric layer, 1-2 is the metal ground plane, 1-3 is the lamination layer, 1-4 is the second dielectric layer, 1-5 is the first metal layer, 1-6 is the third dielectric layer, 1-7 is the second metal layer, 1-8 is the feed microstrip line, and 1-9 is the conductive metal pillar.

[0022] Figure 4 This is a schematic diagram of the structure of the first metal layer in this invention, wherein 1-5-1 is an I-shaped patch, 1-5-2 is a triangular patch, and 1-5-3 is a bend line.

[0023] Figure 5 This is a schematic diagram of the sixteen-part equal-division power supply network in this invention.

[0024] Figure 6 This is a schematic diagram of the structure of the four-phase rotating feeder network in this invention.

[0025] Figure 7 This is a diagram illustrating the dimensional parameters of the polarization conversion radiation unit in this invention.

[0026] Figure 8 This is a schematic diagram of the feeding structure of the ultrawideband RCS reduced circular polarization antenna based on the polarization conversion metasurface in this invention.

[0027] Figure 9 This is an actual sample image of the ultrawideband RCS reduced circular polarized antenna based on a polarization conversion metasurface in this invention.

[0028] Figure 10 The ultrawideband RCS-reduced circularly polarized antenna S based on a polarization-conversion metasurface in this invention 11 The test and simulation curves.

[0029] Figure 11 The figures show the test and simulation curves of the axial ratio and gain of the ultrawideband RCS reduced circular polarization antenna based on the polarization conversion metasurface in this invention.

[0030] Figure 12 These are test and simulation curves of the ultrawideband RCS reduced circular polarization antenna pattern based on polarization conversion metasurface in this invention.

[0031] Figure 13The figures show the test and simulation curves of RCS reduction of the ultrawideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface in this invention.

[0032] Figure 14 The scattering patterns of the ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface at different frequencies are shown in this invention.

[0033] Figure 15 This is a simulation diagram of the RCS reduction angle stability of the ultrawideband RCS-reduced circularly polarized antenna based on a polarization conversion metasurface in this invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] This embodiment provides an ultrawideband RCS-reduced circularly polarized antenna array based on a polarization-conversion metasurface, the structure of which is as follows: Figure 1 As shown, it includes: four radiating subarrays 1, four sixteen-part feed networks 2, one four-part phase rotating feed network 3, and one RF coaxial connector 4. The four radiating subarrays 1 are arranged in a 2×2 checkerboard array. The sixteen-part feed network 2, the four-part phase rotating feed network 3, and the RF coaxial connector 4 together constitute the feed structure. The input end of the four-part phase rotating feed network 3 is connected to the RF coaxial connector 4, and the four output ends of the four-part phase rotating feed network 3 are correspondingly connected to the sixteen-part feed network 2. The sixteen-part feed network 2 is connected to the radiating subarrays one-to-one to achieve feeding.

[0036] Furthermore, the radiation subarray 1 is as follows: Figure 2 As shown, it consists of 16 polarization conversion radiation units arranged in a 4×4 matrix;

[0037] The polarization conversion radiation unit, such as Figure 3As shown, it includes: a first dielectric layer 1-1, a metal ground plane 1-2, a lamination layer 1-3, a second dielectric layer 1-4, a first metal layer 1-5, a third dielectric layer 1-6, a second metal layer 1-7, a feed microstrip line 1-8, and a conductive metal pillar 1-9; wherein, the feed microstrip line 1-8 is disposed on the lower surface of the first dielectric layer 1-1, the metal ground plane 1-2 is disposed on the upper surface of the first dielectric layer 1-1, the second dielectric layer 1-4 is laminated onto the upper surface of the metal ground plane 1-2 through the lamination layer 1-3, and the first metal layer 1-5 is disposed between the second dielectric layer 1-4 and the third dielectric layer 1-7. Between -6, the second metal layer 1-7 is disposed on the upper surface of the third dielectric layer 1-6; the conductive metal pillar 1-9 is disposed through the first dielectric layer 1-1, the metal ground plane 1-2, the lamination layer 1-3, and the second dielectric layer 1-4, and its bottom end is connected (including mechanical and electrical connection) to the feed microstrip line 1-8, and its top end is connected to the first metal layer 1-5. The metal ground plane 1-2 and the lamination layer 1-3 are provided with circular holes corresponding to the conductive metal pillar 1-9 to achieve isolation; the feed microstrip line 1-8 is connected to the output end of the sixteen-part feed network 2, and the polarization conversion radiation unit is fed through the feed structure;

[0038] The first metal layer 1-5 as follows Figure 4 As shown, a graphical structure is adopted, including: an I-shaped patch 1-5-1, two isosceles right-angled triangle patches 1-5-2, and two bend lines 1-5-3; wherein, the I-shaped patch 1-5-1 is arranged along the diagonal of the upper surface of the second dielectric layer 1-4, and the two isosceles right-angled triangle patches 1-5-2 are arranged at diagonal positions along the same diagonal (the right angle sides are arranged along the edge of the second dielectric layer), so that the I-shaped patch 1-5-1 and the isosceles right-angled triangle patches 1-5-2 on both sides approximately form a double-headed arrow shape; the I-shaped patch 1-5-1 and the isosceles right-angled triangle patches 1-5-2 are simultaneously provided with channels to accommodate the bend lines 1-5-3, and the two ends of the bend lines 1-5-3 connect the I-shaped patch 1-5-1 and the isosceles right-angled triangle patches 1-5-2. The triangular patch 1-5-2 and the bend line 1-5-3 are also set along the same diagonal. The structural inductance generated by the subwavelength bend line and the parasitic capacitance generated by the patches at both ends form a parallel LC circuit structure. By adjusting the length of the structural inductance and the parasitic capacitance, a broadband radiation effect can be obtained. It should also be noted that in practical applications, the specific dimensions of the I-shaped patch 1-5-1 and the isosceles right-angled triangular patch 1-5-2 can be adaptively optimized according to technical specifications. Based on the optimized dimensional parameters (including the spacing between the I-shaped patch 1-5-1 and the isosceles right-angled triangular patch 1-5-2), the I-shaped patch 1-5-1 may have a chamfered corner (the chamfered edge is flush with the right-angled side of the isosceles right-angled triangular patch 1-5-2). Figure 4 As shown;

[0039] The second metal layer 1-7 adopts a rectangular coupling patch, which is located at the center of the upper surface of the third dielectric layer 1-6.

[0040] Furthermore, the sixteen-part power distribution network 2 is as follows: Figure 5 As shown, its function is to evenly distribute 25% of the input RF signal to sixteen polarization-conversion radiating units. Theoretically, the power in each unit should be 1.5625% of the signal. Specifically, it includes fifteen 1-to-2 power dividers and multiple reference-connected microstrip lines. Each 1-to-2 power divider contains one input and two outputs. The first power divider 2-1 has its RF signal input at its input terminal and its output directly connected to the input terminals of the second and third power dividers 2-2 and 2-3 via two reference-connected microstrip lines. The two output terminals of the second power divider 2-2 are directly connected to the input terminals of the fourth and fifth power dividers 2-4 and 2-5 via two reference-connected microstrip lines. The two output terminals of the third power divider 2-3 are directly connected to the input terminals of the sixth and seventh power dividers 2-6 and 2-7 via two reference-connected microstrip lines. The two output terminals of the fourth power divider 2-4 are directly connected to the input terminals of the sixth and seventh power dividers 2-7 via two reference-connected microstrip lines. The input terminals of the eighth power divider 2-8 and the ninth power divider 2-9; the two output terminals of the fifth power divider 2-5 are directly connected to the input terminals of the tenth power divider 2-10 and the eleventh power divider 2-11 via two reference connection microstrip lines; the two output terminals of the sixth power divider 2-6 are directly connected to the input terminals of the twelfth power divider 2-12 and the thirteenth power divider 2-13 via two reference connection microstrip lines; the two output terminals of the seventh power divider 2-7 are directly connected to the input terminals of the fourteenth power divider 2-14 and the fifteenth power divider 2-15 via two reference connection microstrip lines; the output terminals of the eighth power divider 2-8, the ninth power divider 2-9, the tenth power divider 2-10, the eleventh power divider 2-11, the twelfth power divider 2-12, the thirteenth power divider 2-13, the fourteenth power divider 2-14, and the fifteenth power divider 2-15 are mechanically and electrically connected to the feed microstrip lines 1-8 of each polarization conversion radiation unit.

[0041] Furthermore, the four-part phase rotating feed network 3, as shown in the figure... Figure 6As shown, it includes: three 1-to-2 power dividers, three phase-shifted microstrip lines, and multiple reference connection microstrip lines. Each 1-to-2 power divider has one input terminal and two output terminals. The input terminal of the sixteenth power divider 3-1 is the RF signal input terminal. One output terminal is directly connected to the seventeenth power divider 3-2 via a microstrip line, and the other output terminal is connected to the input terminal of the eighteenth power divider 3-3 via a 180° phase-shifted microstrip line 3-4. One output terminal of the seventeenth power divider 3-2 is directly connected to the sixteen-equal-division power distribution network via a microstrip line, and the other output terminal is connected via a 90° phase-shifted microstrip line 3-5. The 16-division power divider is connected to the power divider network. One output terminal of the 18th power divider 3-3 is directly connected to the 16-division power divider network via a microstrip line, and the other output terminal is connected to the 16-division power divider network via a 90° phase-shifted microstrip line 3-5, so that the four output ports of the 4-division phase rotating power divider network are sequentially 90° out of phase. In addition, in order to ensure that the four output ports of the 4-division phase rotating power divider network 3 have good isolation and phase difference, 100-ohm resistors 3-6 are used for port isolation at the output terminals of the 17th power divider 3-2 and the 18th power divider 3-3, respectively.

[0042] Based on the design of the four-phase rotating feed network 3, four identical radiating subarrays are rotated by 0°, 90°, 180° and 270° respectively and arranged sequentially at a certain distance. The feed phases are 0°, 90°, 180° and 270° respectively, so that the radiating subarrays rotated by 0° and 180° have the same radiation phase, the radiating subarrays rotated by 90° and 270° have the same radiation phase, and their radiation is linearly polarized radiation. Since the radiation directions of the former and the latter are orthogonal and have a counterclockwise phase difference of 90° on the feed network, right-hand circularly polarized (RHCP) radiation capability is obtained.

[0043] Additionally, it should be noted that in the four-part phase rotating feed network and the sixteen-part power divider feed network described above, all power dividers and phase shift lines use a standard RF system impedance of 50 ohms at their input and output terminals. A microstrip line with an impedance of √2 times the standard impedance is used to connect the input and output terminals of the power dividers, and this microstrip line has a length of one-quarter of the center wavelength of the operating frequency band, thereby achieving impedance matching between the input terminal and the two output terminals.

[0044] Furthermore, the RF coaxial connector 4 enables the conversion from coaxial line to microstrip line, specifically a standard RF coaxial connector with an impedance of 50 ohms.

[0045] The beneficial effects of the present invention will be described in detail below with reference to specific embodiments and tests.

[0046] Common broadband RCS-reduced metasurface circularly polarized antennas suffer from radiation dependence on the multimode resonance characteristics of a finite array due to the characteristic modes generated by the metasurface array, or the inability to achieve ultra-wideband RCS reduction bandwidth due to their single-layer structure. However, metasurface circularly polarized antennas based on a double-layer structure and array feeding can construct an array using the radiation characteristics of individual elements without relying on multimode resonance and achieve good in-band and out-of-band scattering effects. This invention employs an array-fed antenna structure based on a double-layer metasurface, combined with a microstrip power divider and phase-shifted microstrip lines, and applies a subwavelength structure inductor to a polarization-conversion metasurface. A circularly polarized antenna array with ultra-wideband RCS reduction, featuring 64 elements and a 1-to-64 power divider feed network, was designed and verified, achieving high gain. The circularly polarized communication exhibits a 3dB gain bandwidth of 23.68% (13.4-17GHz), a 3dB axial ratio bandwidth of 28.57% (13.2-17.6GHz), and a -10dB impedance bandwidth of 31.93% (12.24-16.89GHz), with a peak gain reaching 14.22dBi. It employs a scattering design based on a checkerboard array to achieve RCS reduction. Combining the checkerboard array arrangement with the polarization conversion characteristics of the polarization conversion radiating unit, it achieves ultra-wideband RCS reduction with good angular stability both in and out of band. The 6dB RCS reduction bandwidth is 110.2% (5.5-19GHz), and the angular stability of RCS reduction in both in-band and near-in-band frequencies reaches 45°. Compared to the existing double-layer metasurface ultrawideband RCS-reduced circularly polarized antennas based on novel feed networks, which have an achievable gain of 11.9 dBi, a 109% RCS reduction bandwidth, and a low-frequency operating band, this invention achieves higher gain, higher aperture utilization efficiency, RCS reduction performance outside the low-frequency band, and good RCS reduction angle stability in the in-band and near-in-band frequencies, while using the same number of array elements.

[0047] The four subarrays of the broadband RCS-reduced metasurface circularly polarized antenna are arranged in a checkerboard pattern, enabling the antenna to reduce its radar cross-section by scattering cancellation. Furthermore, the feed signals of each subarray are equal in amplitude and have phase differences of 0, 90, 180, and 270°, thus achieving the radiation performance of the circularly polarized antenna. Its scattering patterns are as follows: S1-S6 states at 6.33 GHz, 8.11 GHz, 10 GHz, 12 GHz, 14 GHz, and 16 GHz: S1 (6.33 GHz, Back Scattering), S2 (8.11 GHz, Back Scattering), S3 (10 GHz, Back Scattering), S4 (12 GHz, Back Scattering), S5 (14 GHz, Back Scattering), S6 (16 GHz, Back Scattering); and S7-S12 states at 13.5 GHz, 15 GHz, and 16.5 GHz: S7 (13.5 GHz, E...). The coordinate planes are: S8 (15 GHz, E Plane Radiation), S9 (16.5 GHz, E Plane Radiation), S10 (13.5 GHz, H Plane Radiation), S11 (15 GHz, H Plane Radiation), and S12 (16.5 GHz, H Plane Radiation). Back Scattering and Radiation represent backscattering and radiation, respectively; E plane represents the YOZ coordinate plane; and H plane represents the XOZ coordinate plane.

[0048] More specifically, the structural parameters of the ultrawideband RCS-reduced circularly polarized antenna array based on a polarization-conversion metasurface in this embodiment are as follows: Figure 7As shown; the overall dimensions are 60mm × 60mm × 5.49mm, the antenna center operating frequency is f = 15.2GHz, and the corresponding vacuum wavelength is λ0 = 19.7mm. Therefore, 60mm × 60mm × 5.49mm corresponds to 3.04λ0 × 3.04λ0 × 0.278λ0. The polarization conversion radiation unit uses the F4BM220 model, a square shape with a side length of 60mm, a dielectric constant of 2.2, and thicknesses of 0.254mm and 2mm respectively. The dielectric constant fluctuation is ±0.04, and the loss tangent is 0.0013. The second dielectric plate uses... Using F4BTMS220 material as the substrate, a square shape with a side length of 60mm, a dielectric constant of 2.2, a dielectric constant fluctuation of ±0.02, a loss tangent of 0.0009, and a thickness of 3mm is employed. The microstrip line and the first metal layer between the first and second dielectric substrates are connected via metal vias with a diameter of d1 = 0.7mm. One end of the metal via, away from the second dielectric substrate, is electrically and mechanically connected to a 50-ohm microstrip line with a linewidth of w1 = 0.68mm and rounded corners at the connection point. The other end of the metal via is electrically and mechanically connected to an I-shaped patch of the first metal layer. The connection is offset from the center of the first metal layer by l4 = 1.1 mm and is located on the central axis of the patch. The I-shaped patch is narrow in the middle, with a width of w2 = 0.25 mm and a length of w3 = 1 mm, and has a channel at one end with a width of w9 = 1.4 mm and a depth of w10 = 0.8 mm, located on the central axis of the I-shaped patch. A bent line is connected to one end of the channel of the I-shaped patch, and the other end is connected to the channel of the triangular patch. Here, the line width of the bent line is w7 = 0.15 mm, the distance from the edge of the channel is w12 = 0.15 mm, and the depth of the channel of the triangular patch is w8 = 0.45 mm. The near-edge spacing between the chip and the I-shaped patch is w5 = 0.2 mm. The combination of the chip and the triangular patch forms the basic structure of the first metal layer. The bent line, as a subwavelength structure, is equivalent to a structural inductor within the operating frequency band. The coupling between the triangular and I-shaped patches forms a structural capacitor. Therefore, in the equivalent circuit, this structure connected by the bent line constitutes a parallel capacitor and inductor. This results in the first metal layer having high impedance characteristics at the resonant frequency f of the parallel capacitor and inductor, thus leading to wave transmission characteristics near the resonant frequency. The relative wave transmission bandwidth (-0.5 dB insertion loss) can be expressed by the following formula:

[0049]

[0050] Among them, L pFor the inductance in a parallel LC circuit, N = MZ0 / πf0 is a constant, M is the impedance factor, Z0 = 377 ohms is the vacuum wave impedance, and f0 is the electromagnetic wave frequency. From the formula, it can be seen that when the inductance L is reduced... p When the inductance L is increased, it will lead to a decrease in the relative bandwidth of the transmitted wave; when the inductance L is increased, it will lead to a decrease in the relative bandwidth of the transmitted wave. p When the inductance is increased, the relative bandwidth of the transmission wave increases. In the first metal layer, increasing the inductance increases the total length of the bend or narrows the width; conversely, it shortens and widens. Therefore, changing the structural dimensions of the bend can change the transmission characteristics of the polarization conversion radiation unit, i.e., the in-band characteristics. In addition, in a periodic structure with a period of p = 6 mm, due to the reference ground effect of the perforated metal ground, within the considered frequency band, by aligning the first metal layer along the 45° direction, its periodic structure exhibits anisotropy in two orthogonal directions, thereby giving the polarization conversion radiation unit polarization conversion characteristics. The second metal layer is a square patch with a size of l3 = 2.1 mm, which functionally limits the high end of the operating frequency band and maintains the polarization conversion characteristics within the considered frequency band.

[0051] The sixteen-part power divider feed network and the four-part sequential rotating phase feed network are placed at the bottom of the first dielectric substrate. All input and output terminals of the power dividers, as well as microstrip connection lines and phase shift lines, use microstrip lines with a width of w1 = 0.68 mm, ensuring an impedance of 50 ohms for integration with standard RF systems. Additionally, the quarter-wavelength matching line of the power divider has a linewidth of w13 = 0.37 mm and a length of 4.9 mm, approximately one-quarter of the operating center wavelength, with an impedance √2 times the standard impedance of 50 ohms. The parameters are expressed as follows: Figure 8 As shown.

[0052] like Figure 9 The image shown is a physical diagram of the ultra-wideband RCS-reduced circularly polarized antenna of this embodiment. The fabrication and simulation tests performed on it yielded the following results:

[0053] like Figure 10 The figure shows a comparison of the simulation test results of the antenna return loss in the embodiment of the present invention. As can be seen from the figure, the bandwidth when the simulated return loss is greater than 10dB is 31.78% (12.25GHz-16.88GHz), while the test result is 36.73% (12-17.4GHz). The simulation results and the test results are basically consistent, and both show good return loss characteristics within the operating frequency band.

[0054] like Figure 11The figure shows a comparison of simulation tests of axial ratio and gain in an embodiment of the present invention. As can be seen from the figure, the simulated 3dB axial ratio bandwidth is 13.2-17.6GHz, while the test result is 13.3-17.9GHz; the simulated 3dB gain bandwidth is 13.4-17GHz, while the test result is 13.9-17.9GHz, and the test results are basically consistent with the simulation results. Furthermore, within the 3dB gain bandwidth range, the antenna exhibits good axial ratio characteristics, with a peak gain reaching 14.22dBi, making it suitable for circularly polarized communication scenarios.

[0055] like Figure 12 The figure shows a comparison of the simulation test results of the antenna radiation normalization pattern in the embodiment of the present invention. As can be seen from the figure, the radiation patterns of the antenna at the tested frequencies of 13.5 GHz, 15 GHz and 16.5 GHz are basically consistent with those of the simulation. Moreover, the cross polarization (left-hand circular polarization: LHCP) in the same plane is more than 10 dB lower, which shows good circular polarization characteristics.

[0056] like Figure 13 The figure shows a simulation test comparison of RCS reduction in an embodiment of the present invention. As can be seen from the figure, compared with a metal plate of the same size, the simulated 6dB RCS reduction frequency band when a plane wave is incident on the antenna is 5.5-19GHz (110.2%). The RCS reduction results of the antenna show good consistency between simulation and test, thus verifying the ultra-wideband RCS reduction performance of the antenna, which is suitable for electromagnetic compatibility, radar stealth and other scenarios.

[0057] like Figure 14 The figure shows the scattering pattern of the antenna at different frequency points in the embodiment of the present invention. As can be seen from the figure, when a plane wave is incident on the antenna, the incident beam will be scattered to an unimportant direction, thereby obtaining positive RCS reduction performance, which verifies the effectiveness of the checkerboard array arrangement.

[0058] like Figure 15 The figure shows the RCS reduction of the antenna under TE and TM polarized incident waves in an embodiment of the present invention. As can be seen from the figure, under TE polarized plane wave incident waves, the RCS reduction deteriorates to some extent in the low frequency band, but shows 45° angular stability in and around the operating frequency band; under TM polarized plane wave incident waves, the RCS reduction deteriorates to some extent in the low frequency band, but shows 45° angular stability in and around the operating frequency band; therefore, it is verified that the antenna RCS reduction has good angular stability.

[0059] Therefore, the present invention can achieve high-performance circular polarization communication over a wide frequency band, while also exhibiting RCS reduction performance in the ultra-wideband range and angular stability of over 45°.

[0060] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. An ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface, comprising: The device comprises four radiating subarrays, four sixteen-part feed networks, one four-part phase rotating feed network, and one radio frequency coaxial connector. The four radiating subarrays are arranged in a 2×2 checkerboard pattern. The sixteen-part feed network, the four-part phase rotating feed network, and the radio frequency coaxial connector together constitute the feed structure. The input end of the four-part phase rotating feed network is connected to the radio frequency coaxial connector. The four output ends of the four-part phase rotating feed network are connected one-to-one with the sixteen-part feed network. The sixteen-part feed network is connected one-to-one with the radiating subarrays and feeds them. The feed phases of the four radiating subarrays differ by 90° sequentially in a counter-clockwise direction. The radiating subarray consists of 16 polarization conversion radiating units arranged in a 4×4 matrix. Each polarization conversion radiating unit includes: a first dielectric layer, a metal ground plane, a lamination layer, a second dielectric layer, a first metal layer, a third dielectric layer, a second metal layer, a feed microstrip line, and a conductive metal pillar. The feed microstrip line is disposed on the lower surface of the first dielectric layer, the metal ground plane is disposed on the upper surface of the first dielectric layer, the second dielectric layer is laminated onto the upper surface of the metal ground plane via the lamination layer, the first metal layer is disposed between the second and third dielectric layers, and the second metal layer is disposed on the upper surface of the third dielectric layer. The conductive metal pillar penetrates the first dielectric layer, the metal ground plane, the lamination layer, and the second dielectric layer, with its bottom end connected to the feed microstrip line and its top end connected to the first metal layer. The metal ground plane and the lamination layer have circular holes corresponding to the conductive metal pillars for isolation. The feed microstrip line is connected to the output end of a sixteen-part feed network, and the polarization conversion radiating unit is fed through the feed structure.

2. The ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface according to claim 1, characterized in that, The first metal layer adopts a patterned structure, including: one I-shaped patch, two isosceles right-angled triangle patches, and two subwavelength bends; wherein, the I-shaped patch is arranged along the diagonal of the upper surface of the second dielectric layer, and the two isosceles right-angled triangle patches are arranged at diagonal positions along the same diagonal; the I-shaped patch and the isosceles right-angled triangle patches are simultaneously provided with channels to accommodate the bends, and the two ends of the bends connect the I-shaped patch and the isosceles right-angled triangle patches, and the bends are also arranged along the same diagonal.

3. The ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface according to claim 1, characterized in that, The second metal layer uses a rectangular coupling patch, which is located at the center of the upper surface of the third dielectric layer.

4. The ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface according to claim 1, characterized in that, The four radial subarrays adopt the same structure and are arranged at intervals after being rotated by 0°, 90°, 180° and 270° respectively, forming a 2×2 chessboard array.

5. The ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface according to claim 1, characterized in that, The sixteen-level equal-division power distribution network includes 15 one-to-two power dividers, which are connected by a reference microstrip line to achieve 16 equal-amplitude and in-phase outputs.

6. The ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface according to claim 1, characterized in that, The four-phase rotating feed network includes: three 1-to-2 power dividers, one 180° phase-shifted microstrip line, and two 90° phase-shifted microstrip lines. The RF input signal is split into two paths after passing through the first power divider. One path is connected to the second power divider via a reference connection microstrip line, and the other path is connected to the third power divider via the 180° phase-shifted microstrip line. The output of one output terminal of the second and third power dividers is directly output, and the other output terminal is output after passing through the 90° phase-shifted microstrip line, so that the phases of the four output ports of the four-phase rotating feed network are successively 90° apart in a counterclockwise direction.

7. The ultrawideband RCS-reduced circularly polarized antenna based on a polarization-conversion metasurface according to claim 6, characterized in that, In the four-phase rotating power supply network, a resistor is set between the two output terminals of each 1-to-2 power divider for port isolation.

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