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

Abstract

The invention belongs to the technical field of electronic equipment, relates to a radiation and dispersion integrated antenna technology, and provides an ultra-wideband RCS (radar cross section) reduction circularly polarized antenna based on a polarization conversion metasurface, which comprises four radiation sub-arrays, four sixteen-equal feed networks, a quartering phase rotation feed network and a radio frequency coaxial connector, the input end of the quartering phase rotation feed network is connected with the radio frequency coaxial connector, the four output ends of the quartering phase rotation feed network are connected with the sixteen-equal feed network in a one-to-one correspondence mode, and the sixteen-equal feed network is connected with the radiation subarrays in a one-to-one correspondence mode and conducts feed. The feed phases of the four radiation sub-arrays differ by 90 degrees in sequence along the anticlockwise direction; based on this, the circularly polarized antenna provided by the invention realizes high-gain circularly polarized radiation and reception in a working frequency band, and has RCS reduction performance, and the RCS reduction angle stability in the working frequency band is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic equipment, relates to a divergence-radiation integrated antenna technology, and specifically provides an ultra-wideband RCS-reduced circularly polarized antenna based on a polarization conversion metasurface. Background Art

[0002] Compared with traditional antennas, the integrated divergence and radiation antenna achieves integrated control of radiation and scattering through the fusion of metasurface and antenna. Based on the current development of antenna technology, polarization conversion surfaces and artificial magnetic conductors are often used in integrated divergence and radiation low-scattering antennas. The fusion of the two with antenna feeding technology can achieve polarization conversion and radiation functions on the same structure. There is no need for lumped devices, which enhances the utilization of limited space and device life. It also has low profile and low cost characteristics, and is easy to integrate with radar systems. Depending on the implementation method, the eigenmode of the metasurface array and the resonant mode of the metasurface unit can be used to realize various types of integrated divergence and radiation antennas.

[0003] Faced with the increasingly complex application scenario requirements, the divergence-integrated antenna is developing towards the direction of wide passband and wideband radar cross section reduction. For example, as shown in the document "Circularly Polarized Polarization Conversion Metasurface-Inspired Antenna Array With Low RCS Over a Wide Band", Pengfeiwang et al. disclosed a polarization conversion surface-inspired circularly polarized antenna array with broadband RCS reduction, which directly uses the polarization conversion surface unit as an antenna radiator without increasing the complexity of the structure, 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 the advantages of low profile, low cost, low processing difficulty and excellent performance; however, since the antenna is a single-layer structure, the bandwidth of out-of-band RCS reduction is narrow, which limits its functional application. As shown in the document “Ultra-Wideband Low-RCS Circularly Polarized Antennas Realized by Bilayer Polarization Conversion Metasurfaces and Novel Feeding Networks”, Xi Gao et al. disclosed an ultra-wideband low-RCS circularly polarized antenna realized by a double-layer polarization conversion metasurface and a novel feeding network, which realizes a low-frequency broadband circularly polarized passband and an ultra-wideband RCS reduction performance in a high-frequency band together with the polarization conversion surface through four sequentially fed slots and a phase adjustment surface; the ultra-wideband polarization conversion performance can be better adjusted by using the phase adjustment surface, and the polarization conversion surface can be used to make the antenna have a lower profile and broadband radiation performance formed by the characteristic mode mode generated by the polarization conversion surface array; however, due to the radiation performance formed by the characteristic mode, the antenna cannot effectively utilize the aperture of the antenna, which leads to limited gain, and the RCS reduction effect cannot be achieved in the low-frequency part, thereby limiting its functional application; in addition, the angular stability of the RCS reduction of the antenna within the working frequency band is poor. Summary of the invention

[0004] The object of the present invention is to provide an ultra-wideband RCS reduction circularly polarized antenna based on a polarization conversion metasurface, which is used to achieve high-gain circularly polarized radiation and reception in a working frequency band, while having RCS reduction performance, and the angular stability of RCS reduction within the working frequency band is good.

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

[0006] An ultra-wideband RCS-reduced circularly polarized antenna based on a polarization conversion metasurface comprises: 4 radiating subarrays, 4 sixteen-equally divided feeding networks, 1 four-equally divided phase rotation feeding network and 1 radio frequency coaxial connector, characterized in that the four radiating subarrays are arranged in a 2×2 chessboard array, the sixteen-equally divided feeding network, the four-equally divided phase rotation feeding network and the radio frequency coaxial connector together constitute a feeding structure, the input end of the four-equally divided phase rotation feeding network is connected to the radio frequency coaxial connector, the four output ends of the four-equally divided phase rotation feeding network are connected to the sixteen-equally divided feeding network in a one-to-one correspondence, the sixteen-equally divided feeding network is connected to the radiating subarrays in a one-to-one correspondence and feeds, and the feeding phases of the four radiating subarrays differ by 90° in sequence in a counterclockwise direction.

[0007] Furthermore, the radiation subarray is composed of 16 polarization conversion radiation units arranged in a 4×4 matrix, and the polarization conversion radiation unit includes: a first dielectric layer, a metal floor, a laminated layer, a second dielectric layer, a first metal layer, a third dielectric layer, a second metal layer, a feeding microstrip line and a conductive metal column; wherein the feeding microstrip line is arranged on the lower surface of the first dielectric layer, the metal floor is arranged on the upper surface of the first dielectric layer, the second dielectric layer is laminated on the upper surface of the metal floor through the laminated layer, the first metal layer is arranged between the second dielectric layer and the third dielectric layer, and the second metal layer is arranged on the upper surface of the third dielectric layer; the conductive metal column runs through the first dielectric layer, the metal floor, the laminated layer, and the second dielectric layer, and the bottom end is connected to the feeding microstrip line and the top end is connected to the first metal layer, and the metal floor and the laminated layer are provided with circular holes corresponding to the conductive metal columns to achieve isolation; the feeding microstrip line is correspondingly connected to the output end of the sixteen-equal feeding network, and the polarization conversion radiation unit is fed through the feeding structure.

[0008] Furthermore, the first metal layer adopts a graphic structure, including: 1 I-shaped patch, 2 isosceles right-angled triangle patches and 2 sub-wavelength bending lines; wherein, the I-shaped patch is arranged along the diagonal line 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 line; the I-shaped patch and the isosceles right-angled triangle patch simultaneously open channels to accommodate the bending lines, and the two ends of the bending lines connect the I-shaped patch and the isosceles right-angled triangle patch, and the bending lines are also arranged along the same diagonal line.

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

[0010] Furthermore, the four radiation sub-arrays adopt the same structure and are arranged at intervals after being rotated by 0°, 90°, 180° and 270° respectively to form a 2×2 chessboard array arrangement.

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

[0012] Furthermore, the four-equal phase rotation feeding network includes: three one-to-two power dividers, one 180° phase-shifted microstrip line and two 90° phase-shifted microstrip lines, wherein the RF input signal is divided into two paths after passing through the first power divider, one path is connected to the second power divider through the reference connection microstrip line, and the other path is connected to the third power divider through the 180° phase-shifted microstrip line; the second power divider and one output end of the third power divider are directly output, and the other output end is output after passing through the 90° phase-shifted microstrip line, so that the phases of the four output ports of the four-equal phase rotation feeding network differ by 90° in sequence along the counterclockwise direction.

[0013] Furthermore, in the four-equal phase rotation feeding network, a resistor is arranged between two output ends of each one-to-two power divider to perform port isolation.

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

[0015] 1. The ultra-wideband RCS reduction circularly polarized antenna of the present invention can perform high-gain circularly polarized radiation and reception in the band, with a return loss greater than 10dB, an impedance bandwidth of 31.78% (12.25GHz to 16.88GHz), a 3dB gain bandwidth of 13.4-17GHz, a 3dB axial ratio bandwidth of 28.57% (13.2GHz to 17.6GHz), and an in-band peak gain of 14.22dBi, which is suitable for most high-gain transceiver scenarios;

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

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

[0018] 4. The ultra-wideband RCS reduction circularly polarized antenna of the present invention adopts three layers of dielectric material layers and four layers of metal structure layers, which can be realized by stacking PCB boards. It has low cost, does not require lumped devices for the units, and is simple to process. In addition, the overall profile is low, and the size of the radiation unit is about one-quarter of the wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a structural schematic diagram of the ultra-wideband RCS-reduced circularly polarized antenna based on the polarization conversion metasurface in the present invention, wherein 1 is a radiating subarray, 2 is a sixteen-equally divided feeding network, 3 is a four-equally divided phase rotation feeding network, and 4 is a radio frequency coaxial connector.

[0020] Figure 2 It is a schematic diagram of the structure of the radiation sub-array in the present invention.

[0021] Figure 3 It is a schematic diagram of the structure of the polarization conversion radiation unit in the present invention, wherein 1-1 is the first dielectric layer, 1-2 is the metal floor, 1-3 is the laminated 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 feeding microstrip line, and 1-9 is the conductive metal column.

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

[0023] Figure 5 It is a schematic diagram of the structure of the sixteen-equally divided feeding network in the present invention.

[0024] Figure 6 It is a schematic diagram of the structure of the four-equal phase rotation feeding network in the present invention.

[0025] Figure 7 This is a diagram showing the dimension parameters of the polarization conversion radiation unit in the present invention.

[0026] Figure 8 Schematic diagram of the feeding structure of the ultra-wideband RCS-reduced circularly polarized antenna based on the polarization conversion metasurface in the present invention.

[0027] Fig. 9 This is an actual sample diagram of the ultra-wideband RCS-reduced circularly polarized antenna based on the polarization conversion metasurface in the present invention.

[0028] Fig.10 The ultra-wideband RCS-reduced circularly polarized antenna S based on the polarization conversion metasurface of the present invention is 11 Test and simulation curves.

[0029] Fig.11 It is a test and simulation curve diagram of the axial ratio and gain of the ultra-wideband RCS-reduced circularly polarized antenna based on the polarization conversion metasurface in the present invention.

[0030] Fig.12 It is a test and simulation curve diagram of the ultra-wideband RCS-reduced circularly polarized antenna pattern based on the polarization conversion metasurface in the present invention.

[0031] Fig.13It is a test and simulation curve diagram of RCS reduction of the ultra-wideband RCS reduction circularly polarized antenna based on polarization conversion metasurface in the present invention.

[0032] Fig.14 The scattering patterns of the ultra-wideband RCS-reduced circularly polarized antenna at different frequencies based on the polarization conversion metasurface in the present invention.

[0033] Fig.15 This is a simulation diagram of the RCS reduction angle stability of the ultra-wideband RCS reduction circularly polarized antenna based on the polarization conversion metasurface in the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0035] This embodiment provides an ultra-wideband RCS reduction circularly polarized antenna array based on a polarization conversion metasurface, and its structure is as follows: Figure 1 As shown, it includes: four radiating sub-arrays 1, four sixteen-equally divided feeding networks 2, a four-equally divided phase rotation feeding network 3 and a radio frequency coaxial connector 4, wherein the four radiating sub-arrays 1 are arranged in a 2×2 chessboard array, the sixteen-equally divided feeding network 2, the four-equally divided phase rotation feeding network 3 and the radio frequency coaxial connector 4 together constitute a feeding structure, the input end of the four-equally divided phase rotation feeding network 3 is connected to the radio frequency coaxial connector 4, the four output ends of the four-equally divided phase rotation feeding network 3 are correspondingly connected to the sixteen-equally divided feeding network 2, and the sixteen-equally divided feeding network 2 is connected to the radiating sub-arrays one by one to realize feeding.

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

[0037] The polarization conversion radiation unit is as follows Figure 3As shown, it includes: a first dielectric layer 1-1, a metal floor 1-2, a laminating 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 feeding microstrip line 1-8 and a conductive metal column 1-9; wherein the feeding microstrip line 1-8 is arranged on the lower surface of the first dielectric layer 1-1, the metal floor 1-2 is arranged on the upper surface of the first dielectric layer 1-1, the second dielectric layer 1-4 is laminating on the upper surface of the metal floor 1-2 through the laminating layer 1-3, and the first metal layer 1-5 is arranged between the second dielectric layer 1-4 and the third dielectric layer 1 -6, the second metal layer 1-7 is arranged on the upper surface of the third dielectric layer 1-6; the conductive metal column 1-9 penetrates the first dielectric layer 1-1, the metal floor 1-2, the laminated layer 1-3, and the second dielectric layer 1-4, and the bottom end is connected (including mechanical connection and electrical connection) to the feeding microstrip line 1-8, and the top end is connected to the first metal layer 1-5, and the metal floor 1-2 and the laminated layer 1-3 are provided with circular holes corresponding to the conductive metal column 1-9 to achieve isolation; the feeding microstrip line 1-8 is connected to the output end of the sixteen-equally divided feeding network 2, and the polarization conversion radiation unit is fed through the feeding structure;

[0038] The first metal layer 1-5 is 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 bending lines 1-5-3; wherein, the I-shaped patch 1-5-1 is arranged along the diagonal line of the upper surface of the second dielectric layer 1-4, and the two isosceles right-angled triangle patches 1-5-2 are arranged along the diagonal position of the same diagonal line (the right angle side is 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 thereof approximately form a two-way arrow pattern; the I-shaped patch 1-5-1 and the isosceles right-angled triangle patches 1-5-2 simultaneously open channels to accommodate the bending line 1-5-3, and the two ends of the bending line 1-5-3 connect the I-shaped patch 1-5-1 and the isosceles right-angled triangle patches 1-5-2. The I-shaped patch 1-5-2 and the bending line 1-5-3 are also arranged along the same diagonal line. The structural inductance generated by the sub-wavelength bending 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. In addition, it should be noted that: in actual application scenarios, the specific sizes of the I-shaped patch 1-5-1 and the isosceles right-angled triangle patch 1-5-2 can be adaptively optimized according to technical indicators. According to the optimized size parameters (including the spacing between the I-shaped patch 1-5-1 and the isosceles right-angled triangle patch 1-5-2), the I-shaped patch 1-5-1 may be cut corners (the cut corner edge is flush with the right angle side of the isosceles right-angled triangle patch 1-5-2), such as Figure 4 As shown;

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

[0040] Furthermore, the sixteen-equal power distribution feeding network 2 is as follows: Figure 5 As shown, its function is to distribute 25% of the input RF signal evenly to sixteen polarization conversion radiation units. Theoretically, the power on each unit should be 1.5625% of the signal; specifically, it includes: fifteen one-to-two power dividers and multiple reference connection microstrip lines, each one-to-two power divider includes an input end and two output ends; wherein, the input end of the first power divider 2-1 is the RF signal input end, and the output end is directly connected to the input end of the second power divider 2-2 and the third power divider 2-3 through two reference connection microstrip lines; the two output ends of the second power divider 2-2 are directly connected to the input end of the fourth power divider 2-4 and the fifth power divider 2-5 through two reference connection microstrip lines; the two output ends of the third power divider 2-3 are directly connected to the input end of the sixth power divider 2-6 and the seventh power divider 2-7 through two reference connection microstrip lines; the two output ends of the fourth power divider 2-4 are directly connected to the input end of the first power divider 2-5 through two reference connection microstrip lines. The input ends of the eighth power divider 2-8 and the ninth power divider 2-9; the two output ends of the fifth power divider 2-5 are directly connected to the input ends of the tenth power divider 2-10 and the eleventh power divider 2-11 through two reference connection microstrip lines; the two output ends of the sixth power divider 2-6 are directly connected to the input ends of the twelfth power divider 2-12 and the thirteenth power divider 2-13 through two reference connection microstrip lines; the two output ends of the seventh power divider 2-7 are directly connected to the input ends of the fourteenth power divider 2-14 and the fifteenth power divider 2-15 through two reference connection microstrip lines; the output ends 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 correspondingly connected to the feeding microstrip lines 1-8 of each polarization conversion radiation unit for mechanical and electrical connection.

[0041] Furthermore, the four-equal phase rotation feeding network 3 is as follows Figure 6As shown, it includes: three one-to-two power dividers, three phase-shifted microstrip lines and multiple reference connection microstrip lines, each one-to-two power divider includes an input end and two output ends; wherein, the input end of the sixteenth power divider 3-1 is the RF signal input end, one output end is directly connected to the seventeenth power divider 3-2 through a microstrip line, and the other output end is connected to the input end of the eighteenth power divider 3-3 through a 180° phase-shifted microstrip line 3-4; one output end of the seventeenth power divider 3-2 is directly connected to the sixteen-equal power division feeding network through a microstrip line, and the other output end is connected to the sixteenth power division feeding network through a 90° phase-shifted microstrip line 3-5. Connect the sixteen-equal power division feeding network; one output end of the eighteenth power divider 3-3 is directly connected to the sixteen-equal power division feeding network through a microstrip line, and the other output end is connected to the sixteen-equal power division feeding network after passing through a 90° phase-shifted microstrip line 3-5, so that the four output ports of the four-equal phase rotation feeding network are 90° apart in sequence; in addition, in order to make the four output ports of the four-equal phase rotation feeding network 3 have a better isolation effect and phase difference, a resistor 3-6 with a resistance of 100 ohms is used at the output end of the seventeenth power divider 3-2 and the eighteenth power divider 3-3 for port isolation;

[0042] Based on the design of the four-equal phase rotation feeding network 3, four identical radiating subarrays are rotated by 0°, 90°, 180° and 270° respectively and arranged in sequence at a certain distance, and the feeding phases are 0°, 90°, 180° and 270° respectively, so that the radiating subarrays rotated by 0° and 180° have the same radiation phase, and the radiating subarrays rotated by 90° and 270° have the same radiation phase, and their radiations are all 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 feeding network, right-hand circular polarization (RHCP) radiation capability is obtained;

[0043] It should also be noted that in the above-mentioned four-equal phase rotation feeding network and sixteen-equal power division feeding network, the input and output ends of all power dividers and phase shift lines use the RF system standard impedance setting of 50 ohms, and a microstrip line with an impedance of twice the square root of the standard impedance is used to connect the input and output ends of the power divider, and this microstrip line has a length of one-quarter of the center wavelength of the working frequency band, thereby achieving impedance matching between the input end and the two output ends.

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

[0045] The beneficial effects of the present invention are described in detail below in conjunction with specific embodiments and tests.

[0046] The common broadband RCS reduction metasurface circularly polarized antenna has a characteristic mode generated by the metasurface array, which makes the radiation rely on the multi-mode resonance characteristics of the finite array, or cannot achieve ultra-wideband RCS reduction bandwidth due to the single-layer structure. The metasurface circularly polarized antenna based on the double-layer structure and array feeding can form an array with the radiation characteristics of the unit without relying on multi-mode resonance and achieve good in-band and out-of-band scattering effects. The present invention adopts an array-fed antenna structure based on a double-layer metasurface, combines a microstrip power divider and a phase-shifted microstrip line, and applies a sub-wavelength structure inductor to the polarization conversion metasurface. A circularly polarized antenna array with ultra-wideband RCS reduction having sixty-four units and a one-to-sixty-four power division feeding network is designed and verified, achieving a high-gain For circular polarization communication, the 3dB gain bandwidth is 23.68% (13.4-17GHz), the 3dB axial ratio bandwidth is 28.57% (13.2-17.6GHz), the -10dB impedance bandwidth is 31.93% (12.24-16.89GHz), and the peak gain reaches 14.22dBi; a scattering design scheme based on a chessboard array to achieve RCS reduction is adopted, combined with the chessboard array arrangement and the polarization conversion characteristics of the polarization conversion radiating unit, to achieve ultra-wideband RCS reduction with good angular stability both in-band and out-of-band, the 6dB RCS reduction bandwidth is 110.2% (5.5-19GHz), and the angular stability of RCS reduction in the in-band and near-in-band frequency bands reaches 45°. Compared with the existing double-layer metasurface ultra-wideband RCS reduction circularly polarized antenna based on a new feeding network, which has an achievable gain of 11.9dBi, an RCS reduction bandwidth of 109%, and the disadvantages of an operating band at the low end of the frequency, the present invention produces a higher gain while using the same number of array elements, has a higher aperture utilization efficiency, has RCS reduction performance outside the low-frequency band, and has good RCS reduction angle stability in the in-band and near-in-band frequency bands.

[0047] The four sub-arrays of the broadband RCS reduction metasurface circularly polarized antenna are arranged in a chessboard array, so that the antenna has the ability of scattering cancellation to reduce the radar scattering cross section of the antenna. In addition, the feed signal of each sub-array is equal in amplitude and has a phase difference of 0, 90, 180, and 270 degrees in phase to achieve the radiation performance of the circularly polarized antenna. The scattering patterns are respectively in the 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), and S6 (16 GHz, Back Scattering); the radiation patterns are respectively in the S7-S12 states at 13.5 GHz, 15 GHz and 16.5 GHz: S7 (13.5 GHz, E Back Scattering and Radiation represent backscattering and radiation respectively, E plane represents the coordinate plane YOZ, and H plane represents the coordinate plane XOZ.

[0048] More specifically, the structural parameters of the ultra-wideband RCS reduction circularly polarized antenna array based on the polarization conversion metasurface in this embodiment are as follows: Figure 7As shown; the overall size is 60mm×60mm×5.49mm, the antenna center operating frequency f=15.2GHz, the corresponding vacuum wavelength is λ0=19.7mm, then 60mm×60mm×5.49mm corresponds to 3.04λ0×3.04λ0×0.278λ0; the first dielectric plate, the third dielectric plate and the third dielectric plate of the polarization conversion radiation unit are model F4BM220, with a square shape of 60mm side length, a dielectric constant of 2.2, thicknesses of 0.254mm and 2mm respectively, a dielectric constant fluctuation of ±0.04, and a loss tangent of 0.0013; the second dielectric plate uses The F4BTMS220 material is used as the substrate, and the 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 are also used; the microstrip line between the first dielectric plate and the second dielectric plate and the first metal layer are connected by a metal through hole, and the through hole diameter is d1=0.7mm; the end of the metal through hole away from the second dielectric plate is electrically and mechanically connected to a 50-ohm microstrip line, the microstrip line width is w1=0.68mm, and the arc chamfer treatment is performed at the connection end; the other end of the metal through hole is electrically and mechanically connected to the I-shaped patch of the first metal layer The connection position deviates from the center of the first metal layer by l4=1.1mm, and is located on the central axis of the patch; the I-shaped patch is narrow in the middle, with a width of w2=0.25mm and a length of w3=1mm, and has a channel at the end, with a width of w9=1.4mm and a depth of w10=0.8mm, and is located on the central axis of the I-shaped patch; one end of the bending line is connected to the channel of the I-shaped patch, and the other end is connected to the channel of the triangular patch, where the line width of the bending line is w7=0.15mm, and the distance from the edge of the channel is w12=0.15mm, the channel depth of the triangular patch is w8=0.45mm, and the channel depth of the triangular patch is w9=1.4mm and w10=0.8mm. The spacing between the patch and the near edge of the I-shaped patch is w5 = 0.2mm. The basic structure of the first metal layer is formed by the combination of the patch and the triangular patch, in which the meander line is a sub-wavelength structure, which is equivalent to a structural inductor in the working frequency band, and the coupling between the triangular patch and the I-shaped patch forms a structural capacitor. Therefore, in the equivalent circuit, the structure connected by the meander line constitutes a parallel capacitor inductor, so that at the resonant frequency f of the parallel capacitor inductor, the first metal layer has a high impedance characteristic, which will lead to a wave transmission characteristic near the resonant frequency, and the relative wave transmission bandwidth (-0.5dB insertion loss) can be expressed by the following formula:

[0049]

[0050] Among them, L pis the inductance in the parallel LC, N=MZ0 / πf0 is a constant, M is the impedance factor, Z0=377 ohms is the vacuum wave impedance, 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, the relative bandwidth of the wave transmission will decrease. p When the inductance is increased, the relative bandwidth of the wave transmission increases; in the first metal layer, increasing the inductance lengthens the total length of the meander line or narrows the width; otherwise, it shortens and widens; therefore, changing the structural dimensions of the meander line can change the wave transmission characteristics of the polarization conversion radiation unit, that is, the in-band characteristics; in addition, under the periodic structure with a period of p=6mm, 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 so that its periodic structure shows anisotropy in two orthogonal directions, the polarization conversion radiation unit has polarization conversion characteristics; the second metal layer is a square patch with a size of l3=2.1mm, which can functionally limit the high end of the working frequency band and maintain the polarization conversion characteristics within the considered frequency band;

[0051] The sixteen-equal power division feeding network and the four-equal sequential rotation phase feeding network are placed at the bottom of the first dielectric plate. The input and output ends of all power dividers, as well as microstrip connecting lines and phase shift lines, use microstrip lines with a width of w1=0.68mm, so that the impedance is 50 ohms and can be integrated with the standard RF system; in addition, the line width of the quarter-wavelength matching line of the power divider is w13=0.37mm, and the length is 4.9mm, which is approximately one-quarter of the working center wavelength, and the impedance is √2 times the standard impedance of 50 ohms. The parameters are expressed as follows Figure 8 shown.

[0052] like Fig. 9 The figure shows a physical picture of the ultra-wideband RCS reduction circularly polarized antenna of this embodiment, and a processing simulation test is performed on it, and the results are as follows:

[0053] like Fig.10 The figure shows a comparison diagram of the return loss simulation test of the antenna in the embodiment of the present invention. It can be seen from the figure that the bandwidth when the simulated return loss is greater than 10dB is 31.78% (12.25GHz-16.88GHz), and the test result is 36.73% (12-17.4Ghz). The simulation and test results are basically consistent, and good return loss characteristics are shown in the working frequency band.

[0054] like Fig.11The figure shows a comparison diagram of the simulation test of the axial ratio and gain in the embodiment of the present invention. It can be seen from the figure that the simulated 3dB axial ratio bandwidth is 13.2-17.6GHz, and the test result is 13.3-17.9GHz; the simulated 3dB gain bandwidth is 13.4-17GHz, and the test result is 13.9-17.9GHz, and the test results are basically consistent with the simulation results; in addition, within the 3dB gain bandwidth range, the antenna shows a good axial ratio characteristic, and the peak gain reaches 14.22dBi, which is suitable for circular polarization communication scenarios;

[0055] like Fig.12 The figure shows a comparison diagram of the simulation test of the normalized radiation pattern of the antenna in the embodiment of the present invention. It can be seen from the figure that the radiation pattern of the antenna tested at 13.5 GHz, 15 GHz and 16.5 GHz is basically consistent with the simulated radiation pattern, and the cross polarization (left-hand circular polarization: LHCP) in the same plane is more than 10 dB lower, which has good circular polarization characteristics.

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

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

[0058] like Fig.15 The figure shows the RCS reduction diagram of the antenna in the embodiment of the present invention under the conditions of TE and TM polarized incident waves. It can be seen from the figure that under the TE polarized plane wave incidence, the RCS reduction has a certain deterioration in the low frequency band, but shows an angle stability of 45° in and around the working frequency band; under the TM polarized plane wave incidence, the RCS reduction has a certain deterioration in the low frequency band, but shows an angle stability of 45° in and around the working frequency band; therefore, it is verified that the antenna RCS reduction has good angle stability;

[0059] It can be seen that the present invention can achieve circular polarization communication with good performance in a wider frequency band, and at the same time, can have RCS reduction performance in an ultra-wideband range and have an angle stability of more than 45°.

[0060] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. An ultra-wideband RCS-reduced circularly polarized antenna based on a polarization conversion metasurface, comprising: 4 radiating subarrays, 4 sixteen-equally divided feeding networks, 1 four-equally divided phase rotation feeding network and 1 radio frequency coaxial connector, characterized in that the 4 radiating subarrays are arranged in a 2×2 chessboard array, the sixteen-equally divided feeding network, the four-equally divided phase rotation feeding network and the radio frequency coaxial connector together constitute a feeding structure, the input end of the four-equally divided phase rotation feeding network is connected to the radio frequency coaxial connector, the four output ends of the four-equally divided phase rotation feeding network are connected to the sixteen-equally divided feeding network one by one, the sixteen-equally divided feeding network is connected to the radiating subarrays one by one and feeds, and the feeding phases of the four radiating subarrays differ by 90° in the counterclockwise direction.

2. According to claim 1, the ultra-wideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface is characterized in that: The radiation subarray is composed of 16 polarization conversion radiation units arranged in a 4×4 matrix, and the polarization conversion radiation unit includes: a first dielectric layer, a metal floor, a laminated layer, a second dielectric layer, a first metal layer, a third dielectric layer, a second metal layer, a feeding microstrip line and a conductive metal column; wherein the feeding microstrip line is arranged on the lower surface of the first dielectric layer, the metal floor is arranged on the upper surface of the first dielectric layer, the second dielectric layer is laminated on the upper surface of the metal floor through the laminated layer, the first metal layer is arranged between the second dielectric layer and the third dielectric layer, and the second metal layer is arranged on the upper surface of the third dielectric layer; the conductive metal column runs through the first dielectric layer, the metal floor, the laminated layer, and the second dielectric layer, and the bottom end is connected to the feeding microstrip line and the top end is connected to the first metal layer, and the metal floor and the laminated layer are provided with circular holes corresponding to the conductive metal columns to achieve isolation; the feeding microstrip line is correspondingly connected to the output end of the sixteen-equal feeding network, and the polarization conversion radiation unit is fed through the feeding structure.

3. According to claim 2, the ultra-wideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface is characterized in that: The first metal layer adopts a graphic structure, including: 1 I-shaped patch, 2 isosceles right-angled triangle patches and 2 sub-wavelength bending lines; wherein the I-shaped patch is arranged along the diagonal line 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 line; the I-shaped patch and the isosceles right-angled triangle patch simultaneously open channels to accommodate the bending lines, and the two ends of the bending lines connect the I-shaped patch and the isosceles right-angled triangle patch, and the bending lines are also arranged along the same diagonal line.

4. According to claim 2, the ultra-wideband RCS reduction circularly polarized antenna based on polarization conversion metasurface is characterized in that: The second metal layer adopts a rectangular coupling patch, and the rectangular coupling patch is located at the center of the upper surface of the third dielectric layer.

5. According to claim 1, the ultra-wideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface is characterized in that: The four radiation sub-arrays adopt the same structure and are arranged at intervals after being rotated by 0°, 90°, 180° and 270° respectively to form a 2×2 chessboard array arrangement.

6. The ultra-wideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface according to claim 1, characterized in that: The sixteen-equal power division feeding network includes: 15 one-to-two power dividers, and the one-to-two power dividers are connected by reference connection microstrip lines to achieve 16 equal-amplitude and in-phase outputs.

7. The ultra-wideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface according to claim 1, characterized in that: The four-equal phase rotation feeding network comprises: three one-to-two power dividers, one 180° phase-shifted microstrip line and two 90° phase-shifted microstrip lines, wherein the radio frequency input signal is divided into two paths after passing through the first power divider, one path is connected to the second power divider through the reference connection microstrip line, and the other path is connected to the third power divider through the 180° phase-shifted microstrip line; the second power divider and one output end of the third power divider are directly output, and the other output end is output after passing through the 90° phase-shifted microstrip line, so that the phases of the four output ports of the four-equal phase rotation feeding network differ by 90° in sequence along the counterclockwise direction.

8. The ultra-wideband RCS-reduced circularly polarized antenna based on polarization conversion metasurface according to claim 7, characterized in that: In the four-equal phase rotation feeding network, a resistor is arranged between two output ends of each one-to-two power divider to perform port isolation.

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