Broadband circularly polarized metasurface antenna with in-band and out-of-band radar scattering cross section reduction

Abstract

The invention discloses a broadband circular polarization metasurface antenna with in-band and out-of-band radar scattering cross section reduction, which comprises an upper layer structure with a metasurface and a lower layer structure with a feed network, and is characterized in that the upper layer structure and the lower layer structure are connected through a bonding layer formed by RO4450F prepregs in the middle layer; the upper layer structure is formed by connecting a metasurface metal patch, a first dielectric substrate and a metal floor from top to bottom; 16 unit structures are arranged into 4 * 4 units to form the metasurface, and metal patches of each unit comprise a C-shaped metal patch, a circular metal patch and an L-shaped metal patch; the lower layer structure comprises a second dielectric substrate and a feed network; and the circular metal patch is respectively connected with the metal floor and the feed network through the short circuit probe and the feed probe. By adopting the technical scheme of the invention, the antenna has the characteristics of broadband left-hand circular polarization radiation and low profile, and has the performance of reducing the in-band and out-of-band radar scattering cross sections of the working bandwidth of the antenna at the same time.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology, and in particular relates to a broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar scattering cross section. Background Art

[0002] Antennas are key components in modern military communications systems. With advances in radar detection technology, stealth is becoming increasingly important. However, traditional antenna designs, due to their metallic structure and open radiation characteristics, often become primary targets for enemy radars. Therefore, reducing the radar cross section (RCS) of antennas, a major scattering source, while maintaining their radiation performance has become a critical issue.

[0003] Methods for reducing antenna RCS primarily include artificial magnetic conductors (AMCs), loaded absorbers, and PB phase. The AMC RCS reduction mechanism relies on a 180°±37° phase difference between its reflected phase and that of the metal, achieving phase cancellation at specific frequencies, significantly reducing the antenna's RCS. This method has a relatively simple structure, but is limited in bandwidth and typically only effective within a narrowband range. Loaded absorbers, on the other hand, incorporate electromagnetic absorbing materials or metamaterials to dissipate incident energy into heat, suppressing electromagnetic wave reflection. This method offers good RCS reduction, but its large overall profile makes integration difficult. PB phase-based RCS reduction relies on geometric phase control within the unit structure, resulting in spatially directional redistribution of scattered waves from different units, thereby reducing the amount of scattered energy in a particular direction. This method offers excellent broadband characteristics and polarization adaptability, but places high demands on phase accuracy and array layout in practical designs. At present, although all of the above technologies can achieve different degrees of RCS reduction, there are still challenges in balancing broadband RCS reduction, antenna radiation performance, profile height and design complexity. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar scattering cross-section.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section comprises an upper structure having a metasurface and a lower structure having a feed network, wherein the upper structure and the lower structure are connected by an adhesive layer formed of an intermediate RO4450F prepreg.

[0007] Preferably, the upper structure includes: a metasurface metal patch, a first dielectric substrate and a metal floor connected from top to bottom; 16 unit structures are arranged into 4×4 units to form a metasurface, and the metal patch of each unit includes: a C-shaped metal patch, a circular metal patch, and an L-shaped metal patch, and the C-shaped metal patch, the circular metal patch, and the L-shaped metal patch are not connected to each other; the short-circuit needle connects the circular metal patch and the metal floor, and the feeding probe connects the circular metal patch and the feeding network.

[0008] Preferably, the lower structure includes: a second dielectric substrate, on which a 1:16 broadband sequential rotation feeding network is provided; the feeding network includes: a 180-degree phase shifter, a first 90-degree phase shifter, a second 90-degree phase shifter, a first Wilkinson power divider, a second Wilkinson power divider, a third Wilkinson power divider, eight T-shaped power dividers and a microstrip transmission line; wherein the feeding network is connected to the input and output ends of the external signal through the microstrip transmission line, and the microstrip transmission line is connected to the first Wilkinson power divider; the first Wilkinson power divider is connected to the 180-degree phase shifter and the 18 corresponding to the 180-degree phase shifter through two mirror-symmetrical curved microstrip lines. The 180-degree phase shifter and the 180-degree reference microstrip line are connected to the second Wilkinson power divider and the third Wilkinson power divider respectively; the second Wilkinson power divider is connected to the first 90-degree phase shifter and the first 90-degree reference microstrip line corresponding to the first 90-degree phase shifter respectively; the first 90-degree phase shifter and the first 90-degree reference microstrip line are connected to four T-shaped power dividers respectively; the third Wilkinson power divider is connected to the second 90-degree phase shifter and the second 90-degree reference microstrip line corresponding to the second 90-degree phase shifter respectively, and the second 90-degree phase shifter and the second 90-degree reference microstrip line are connected to the four T-shaped power dividers respectively.

[0009] Preferably, the first dielectric substrate is an F4BM265 dielectric substrate with h1=3 mm.

[0010] Preferably, the second dielectric substrate is an F4BM265 dielectric substrate with h3=0.1 mm.

[0011] Preferably, the adhesive layer is a RO4450F prepreg with h2=0.2 mm.

[0012] Preferably, the thickness of the C-shaped metal patch, the circular metal patch, and the L-shaped metal patch are all 0.018 mm, and all metal materials are copper.

[0013] The technical solution of the present invention has the characteristics of broadband left-hand circularly polarized radiation and low profile, and simultaneously has the performance of reducing the radar cross section within and outside the antenna working bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0015] Figure 1 Schematic diagram of the structure of a broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to an embodiment of the present invention;

[0016] Figure 2 is the structural diagram of the unit; Figure 2 (a) is the three-dimensional assembly structure diagram of the unit, Figure 2 (b) is a top view of the unit structure;

[0017] Figure 3 is a schematic diagram of the simulated radiation performance of the unit; Figure 3 (a) is the unit radiation |S varying with frequency 11 |Performance curve diagram, Figure 3 (b) is a schematic diagram of the gain change curve of the unit radiation as the frequency changes;

[0018] Figure 4 is a schematic diagram of the simulated polarization conversion performance of the unit; Figure 4 (a) is a schematic diagram of the co-polarization and cross-polarization reflection amplitude performance curves of the unit. Figure 4 (b) is a schematic diagram of the polarization conversion rate performance curve of the unit;

[0019] Figure 5 is a planar structural view of the metasurface antenna; wherein, Figure 5 (a) is a planar structural view of the upper 16 units of the metasurface antenna; Figure 5 (b) A planar structural view of the 1-to-16 feed network at the lower layer of the metasurface antenna.

[0020] Figure 6 A three-dimensional assembly diagram of the 90-degree phase shifter used in the feed network;

[0021] Figure 7 This is a three-dimensional assembly structure diagram of the 180-degree phase shifter used in the feed network;

[0022] Figure 8 The first 90-degree reference microstrip line used in the feeding network;

[0023] Figure 9 The second 90-degree reference microstrip line used in the feeding network;

[0024] Figure 10180-degree reference microstrip line used in the feeding network;

[0025] Figure 11 This is a planar structural view of the Wilkinson power divider used in the feeding network;

[0026] Figure 12 Schematic diagram of the T-shaped power splitter used in the feeding network;

[0027] Figure 13 is the simulation performance of the feeding network; where, Figure 13 (a) is a schematic diagram of the S parameter curve of the feeding network. Figure 13 (b) is a schematic diagram of the phase difference between adjacent ports of the feeding network;

[0028] Figure 14 is the simulated radiation performance of the metasurface antenna; where, Figure 14 (a) is the |S of the metasurface antenna 11 |Performance curve diagram, Figure 14 (b) is a schematic diagram of the axial ratio performance curve of the metasurface antenna. Figure 14 (c) is a schematic diagram of the gain performance curve of the metasurface antenna. Figure 14 (d) is a schematic diagram of the efficiency curve of the metasurface antenna;

[0029] Figure 15 is the simulated normalized radiation pattern of the metasurface antenna; where, Figure 15 (a) and Figure 15 (b) are the normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 9GHz, Figure 15 (c) and Figure 15 (d) are the normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 10 GHz, Figure 15 (e) and Figure 15 (f) are the normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 11 GHz, respectively. Figure 15 (g) and Figure 15 (h) The normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 12 GHz, respectively;

[0030] Figure 16 Schematic diagram of the simulated single-station RCS reduction performance of the metasurface antenna. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1:

[0034] like Figure 1 As shown, an embodiment of the present invention provides a broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar scattering cross-section, comprising: an upper structure having a metasurface and a lower structure having a feeding network, the upper structure and the lower structure being connected by an adhesive layer composed of an RO4450F semi-cured sheet with a middle layer height of h2=3mm.

[0035] As an implementation method of an embodiment of the present invention, the upper structure includes: a metasurface metal patch, a first dielectric substrate and a metal floor connected from top to bottom, wherein the first dielectric substrate is an F4BM265 dielectric substrate with h1=3mm, and the relative dielectric constant ε of the F4BM265 dielectric substrate is r =2.65, loss tangent tanδ=0.0013; 16 unit structures are arranged into 4×4 units to form a metasurface, and the metal patches of each unit include: C-shaped metal patches, circular metal patches, and L-shaped metal patches, and the C-shaped metal patches, circular metal patches, and L-shaped metal patches are not connected to each other; the short-circuit pin connects the circular metal patch to the metal floor, and the feed probe connects the circular metal patch to the feed network; the thickness of the C-shaped metal patch, circular metal patch, and L-shaped metal patch is 0.018 mm, and all metal materials are copper.

[0036] As an implementation method of an embodiment of the present invention, the lower structure includes: a second dielectric substrate, a 1:16 broadband sequential rotation feeding network is provided on the second substrate, the second dielectric substrate is an F4BM265 dielectric substrate with h3 = 0.1 mm, and the relative dielectric constant ε of the F4BM265 dielectric substrate is r=2.65, loss tangent tanδ=0.0013; the feeding network includes: a 180-degree phase shifter, a first 90-degree phase shifter, a second 90-degree phase shifter, a first Wilkinson power divider, a second Wilkinson power divider, a third Wilkinson power divider, eight T-shaped power dividers, and a microstrip transmission line; wherein the feeding network is connected to the input and output ends of the external signal via the microstrip transmission line, and the microstrip transmission line is connected to the first Wilkinson power divider; the first Wilkinson power divider is connected to the 180-degree phase shifter and a reference microstrip line corresponding to the 180-degree phase shifter (hereinafter referred to as the 180-degree reference microstrip line) via two mirror-symmetrical curved microstrip lines. The 180-degree phase shifter and the 180-degree reference microstrip line are connected to the second and third Wilkinson power dividers, respectively. The second Wilkinson power divider is connected to the first 90-degree phase shifter and the reference microstrip line corresponding to the first 90-degree phase shifter (hereinafter referred to as the first 90-degree reference microstrip line). The first 90-degree phase shifter and the first 90-degree reference microstrip line are connected to four T-shaped power dividers, respectively. Similarly, the third Wilkinson power divider is connected to the second 90-degree phase shifter and the reference microstrip line corresponding to the second 90-degree phase shifter (hereinafter referred to as the second 90-degree reference microstrip line). The second 90-degree phase shifter and the second 90-degree reference microstrip line are connected to four T-shaped power dividers, respectively.

[0037] In one embodiment of the present invention, Figure 2 The structure diagram of the unit is shown in FIG. Figure 2 (a) is the three-dimensional assembly structure diagram of the unit, Figure 2 (b) is a top-down view of the cell structure. The cell structure period is p = 13 mm, the dielectric substrate thickness is h1 = 1 mm, the feed probe diameter is d1 = 0.7 mm, the shorting pin diameter is d2 = 0.4 mm, the circular metal patch diameter is d3 = 3.4 mm, the circular cavity in the metal floor for the feed probe has a diameter of d4 = 1.4 mm, the short straight side of the C-shaped metal patch parallel to the v direction has a length of l1 = 0.7 mm, the long straight sides parallel to the x and y directions have a length of l2 = 6.6 mm, the L-shaped metal patch has a length of l3 = 3.4 mm, the vertical distance from the center of the feed probe to the nearest cell boundary is l4 = 3.7 mm, the distance between the center of the feed probe and the center of the shorting pin in the y direction is l5 = 0.9 mm, the L-shaped metal patch has a width of w1 = 0.9 mm, and the gap between the circular metal patch and the C-shaped metal patch has a width of w2 = 0.8 mm.

[0038] In one embodiment of the present invention, Figure 3 As shown, it is the simulated radiation performance of the unit. Figure 3 (a) is the unit radiation changing with frequency |S 11 |Performance curve, it can be seen that the unit |S 11| Less than -10dB at 8.3–12.7GHz, indicating that the unit has good impedance matching over a wide frequency range. Figure 3 (b) is the gain variation curve of the unit radiation with frequency. It can be seen that the unit has a maximum gain of 5.8dBi at 11GHz.

[0039] In one embodiment of the present invention, Figure 4 Shown is the simulated polarization conversion performance of the unit. Figure 4 (a) is the co-polarization and cross-polarization reflection amplitude performance curve of the unit, where r xy When the y-polarized wave is incident vertically, the reflected wave is the proportion of the x-polarized wave, which is defined as r xy =|E rx | / |E iy |. Similarly, r yy When the y-polarized wave is incident vertically, the reflected wave is the proportion of the y-polarized wave, which is defined as r yy =|E ry | / |E iy |, r yx Refers to the proportion of the reflected wave that is y-polarized when the x-polarized wave is incident vertically, and the definition is r yx =|E ry | / |E ix |, r xx When the x-polarized wave is incident vertically, the reflected wave is the proportion of x-polarized wave, which is defined as r xx =|E rx | / |E ix |, it can be seen that the co-polarization and cross-polarization reflection amplitudes of the unit are consistent in the two cases of vertical incidence of x-polarized wave and vertical incidence of y-polarized wave. Figure 4 (b) is the polarization conversion rate performance curve of the unit, and the polarization conversion rate is defined as or The polarization conversion efficiency (PCE) measures the polarization conversion capability of a structure. It can be seen that the cell has a PCE greater than 80% in the wideband range of 7.8–17 GHz.

[0040] In one embodiment of the present invention, Figure 5 Shown is a planar structural view of the metasurface antenna. Figure 5 (a) is a planar structural view of the upper 16 units of the metasurface antenna. It can be seen that these 16 units are arranged in a 2×2 sub-array consisting of 4 units, which are rotated around the center point of the entire metasurface to obtain a 4×4 checkerboard arrangement. This arrangement can not only provide the necessary 90-degree spatial phase compensation for circularly polarized radiation, but also achieve single-station RCS reduction through phase cancellation of scattered waves between the 2×2 sub-arrays. Figure 5(b) is a planar structural view of the 1-to-16 feeding network of the lower layer of the metasurface antenna. Port 1 is the input port. Through the first Wilkinson power divider, the second Wilkinson power divider, the third Wilkinson power divider, the 180-degree phase shifter, the 180-degree reference microstrip line, the first 90-degree phase shifter, the first 90-degree reference microstrip line, the second 90-degree phase shifter, the second 90-degree reference microstrip line, eight T-shaped power dividers and the microstrip lines connecting them as shown in the figure, the output power of ports 2, 3, 4 and 5 in the operating frequency band of 7.4–15.8 GHz is basically equal, and the phase difference between adjacent ports is close to 90 degrees.

[0041] In one embodiment of the present invention, Figure 6 The figure shows the three-dimensional assembly structure of the 90-degree phase shifter used in the feed network. The 90-degree phase shifter consists of two layers of metal patches facing each other in the z-axis direction. The upper layer contains two rectangular metal patches, both of which are l ps90 =4.4mm and the width is w ps90 =0.4mm, the gap width w between the two rectangular metal patches gap90 =0.2mm. The lower layer contains only a rectangular metal patch with a length of l rec90 =7.3mm and width w ps90 = 0.4mm. The midpoint of the gap between the two rectangular metal patches on the upper layer aligns with the midpoint of the rectangular metal patch on the lower layer. In this figure, the structure with a thickness of h3 = 0.1mm is the second dielectric substrate in the overall structure, and the structure with a thickness of h2 = 0.2mm is the adhesive layer in the overall structure.

[0042] In one embodiment of the present invention, Figure 7 The figure shows the 3D assembly structure of the 180-degree phase shifter used in the feed network. The 180-degree phase shifter consists of two layers of metal patches facing each other in the z-axis direction. The upper layer contains three rectangular metal patches, and the two shorter rectangular metal patches on both sides are of the same size and have a length of l. ps180 =4.4mm and the width is w ps180 =0.4mm, a longer rectangular metal patch in the middle, with a width of w ps180 =0.4mm, the gap width between the longer rectangular metal patch and the two shorter rectangular metal patches is w gap180 =0.2mm. The lower layer contains two rectangular metal patches of the same size, with a length of l rec90 =7mm and width w ps180= 0.4mm. The midpoints of the two gaps between the three rectangular metal patches on the upper layer align with the midpoints of the two rectangular metal patches on the lower layer. In this figure, the structure with a thickness of h3 = 0.1mm is the second dielectric substrate in the overall structure, and the structure with a thickness of h2 = 0.2mm is the adhesive layer in the overall structure.

[0043] In one embodiment of the present invention, Figure 8 The figure shows the first 90-degree reference microstrip line used in the feed network. The first 90-degree reference microstrip line consists of five sections with a width of w line =0.75mm microstrip line, the length of the first microstrip line is l 90d11 =2mm, the length of the second microstrip line is l 90d12 =0.9mm, the length of the third microstrip line is l 90d13 =5.3mm, the length of the fourth microstrip line is l 90d14 =0.9mm, the length of the fifth microstrip line is l 90d15 =2mm, and a 45-degree chamfer is added to each microstrip line corner.

[0044] In one embodiment of the present invention, Figure 9 As shown, the second 90-degree reference microstrip line used in the feed network is composed of five sections with a width of w. line =0.75mm microstrip line, the length of the first microstrip line is l 90d21 =2mm, the length of the second microstrip line is l 90d22 =3.4mm, the length of the third microstrip line is l 90d23 =4.2mm, the length of the fourth microstrip line is l 90d24 =3.4mm, the length of the fifth microstrip line is l 90d25 =2mm, and a 45-degree chamfer is added to each microstrip line corner.

[0045] In one embodiment of the present invention, Figure 10 As shown, this is the 180-degree reference microstrip line used in the feed network. The 180-degree reference microstrip line consists of nine segments with the same width of w. line =0.75mm microstrip line, the length of the first microstrip line is l 180d1 =6mm, the length of the second microstrip line is l 180d2 =0.6mm, the length of the third microstrip line is l 180d3 =4mm, the length of the fourth microstrip line is l 180d4 =0.6mm, the length of the fifth microstrip line is l 180d5 =1.3mm, the length of the sixth microstrip line is l 180d6 =2.4mm, length of the seventh microstrip line l 180d7 =3.1mm, the length of the eighth microstrip line is l180d8 =2.4mm, the length of the ninth microstrip line is l 180d9 =1mm, and a 45-degree chamfer is added to each microstrip line corner.

[0046] In one embodiment of the present invention, Figure 11 The figure shows the planar structure of the Wilkinson power divider used in the feed network. This Wilkinson power divider is a second-order Wilkinson power divider. Each order Wilkinson power divider consists of three microstrip lines and one resistor. Except for the position where the resistor contacts the microstrip line, each microstrip line corner is chamfered at 45 degrees. The two-order Wilkinson power dividers are connected by two parallel microstrip lines. The width of each microstrip line of the first-order Wilkinson power divider is wpd1 = 0.65mm, and the length of the first microstrip line of the first-order Wilkinson power divider is l 11 =1.55mm, the length of the second microstrip line of the first-order Wilkinson power divider l 12 =2.4mm, the length of the third microstrip line of the first-order Wilkinson power divider l 13 =1.4mm, the resistor corresponding to the first-order Wilkinson power divider is 0603 package size, and the resistance value is R1 = 240Ω. The length of the first microstrip line of the second-order Wilkinson power divider is l 21 =1.6mm, the length of the second microstrip line of the second-order Wilkinson power divider l 22 =1.6mm, the length of the third microstrip line of the second-order Wilkinson power divider l 23 =1.1mm, the resistor corresponding to the second-order Wilkinson power divider is 0603 package size, and the resistance value R2 = 100Ω. The two parallel microstrip lines connecting the first-order Wilkinson power divider and the second-order Wilkinson power divider have a width of w pdm =0.5mm, length is l pdm =0.9mm. The line widths of the input, output 1 and output 2 of the Wilkinson power divider are all w line =0.75mm.

[0047] In one embodiment of the present invention, Figure 12 The figure shows the T-shaped power divider used in the feed network. The T-shaped power divider consists of five rectangular microstrip lines and two annular metal rings. The width of the first microstrip line is w t =0.4mm and length l t1 =4.8mm, the width of the second microstrip line w line =0.75mm and length l t2 =1.1mm, the width of the third and fourth microstrip lines are both w t =0.4mm and the length is l t3=5.6mm, and each rectangular microstrip line corner is chamfered at 45 degrees. The inner diameter of the two annular metal rings is d1 = 0.7mm, and the outer diameter is d t =1.1mm.

[0048] In one embodiment of the present invention, Figure 13 Figure 2 shows the simulated performance of the feeding network. Figure 13 (a) is the S parameter curve of the feeding network, |S 11 |、|S 21 |、|S 31 |、|S 41 |、|S 51 | respectively represent the return losses of port 1, port 2, port 3, port 4, and port 5 when port 1 is input. It can be seen that |S 11 |Less than -10dB in the wide frequency range of 7.4–15.8GHz, |S 21 |、|S 31 |、|S 41 |、|S 51 | is basically equal and close to -6dB in the wide frequency range of 7.4–15.8GHz, Figure 13 (b) is the phase difference between adjacent ports of the feeding network. It can be seen that S 31 With S 21 Phase difference, S 41 With S 31 Phase difference, S 51 With S 41 Phase difference, S 21 With S 51 The phase difference is basically equal and close to 90° in the wide frequency band range of 7.4–15.8 GHz. Figure 13 (a) and Figure 13 (b) shows that the feeding network has the characteristic of sequential rotation in a wide frequency band, which is an important basis for the metasurface antenna to have broadband left-handed circularly polarized radiation characteristics.

[0049] In one embodiment of the present invention, Figure 14 Shown is the simulated radiation performance of the metasurface antenna. Figure 14 (a) is the |S of the metasurface antenna 11 | performance curve, it can be seen that the |S 11 |The bandwidth less than -10dB, i.e., the impedance bandwidth, is 86% (6.5–16.3GHz). Figure 14 (b) is the axial ratio performance curve of the metasurface antenna. It can be seen that the bandwidth where the axial ratio of the metasurface antenna is less than 3dB, that is, the axial ratio bandwidth is 65.5% (7.4–14.6GHz). Figure 14(c) shows the gain performance curve of the metasurface antenna. It can be seen that the gain bandwidth, over which the gain of the metasurface antenna drops less than 3 dB from its maximum value, is 49.3% (8.4–13.9 GHz). Taking the intersection of the impedance bandwidth, axial ratio bandwidth, and gain bandwidth, we can determine that the operating bandwidth of the metasurface antenna is 49.3% (8.4–13.9 GHz), with a maximum gain of 14.6 dBic. Figure 14 (d) is the efficiency curve of the metasurface antenna, including radiation efficiency and overall efficiency. The radiation efficiency and overall efficiency range from 69.3% to 85.3% and 68.5% to 84.8%, respectively, within the operating bandwidth of 8.4–13.9 GHz, indicating that the antenna maintains high efficiency within the wide-band operating bandwidth.

[0050] In one embodiment of the present invention, Figure 15 Shown is the simulated normalized radiation pattern of the metasurface antenna. Figure 15 (a) and Figure 15 (b) The normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 9 GHz, respectively. Figure 15 (c) and Figure 15 (d) are the normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 10 GHz, respectively. Figure 15 (e) and Figure 15 (f) are the normalized radiation patterns of the xoz plane and yoz plane of the metasurface antenna at 11 GHz, respectively. Figure 15 (g) and Figure 15 (h) are the normalized radiation patterns of the xoz plane and the yoz plane of the metasurface antenna at 12GHz, respectively. The solid lines in the above normalized radiation patterns represent the radiation patterns of left-hand circular polarization, and the dotted lines represent the radiation patterns of right-hand circular polarization. It can be seen that the main polarization of the metasurface antenna, i.e., the radiation pattern of left-hand circular polarization, is focused and stable in the direction of the line of sight, and the metasurface antenna has good polarization isolation in a wide bandwidth in the direction of the line of sight. In addition, the metasurface antenna also has low side lobes. The above simulation results show that the metasurface antenna has the characteristics of broadband left-hand circularly polarized radiation.

[0051] In one embodiment of the present invention, Figure 16Figure 2 shows the simulated monostatic RCS reduction performance of the metasurface antenna. The solid and dashed lines in the figure represent the cases of vertical x- and y-polarized wave incidence, respectively. It can be seen that for vertical x-polarized wave incidence, the bandwidth over which the metasurface antenna's monostatic RCS is reduced by more than 10 dB compared to the monostatic RCS of a metal floor of the same size is 71.3% (8.3–17.5 GHz). For vertical y-polarized wave incidence, the bandwidth over which the metasurface antenna's monostatic RCS is reduced by more than 10 dB compared to the monostatic RCS of a metal floor of the same size is 71.9% (8.1–17.2 GHz). The simulation results show that the 10 dB monostatic RCS reduction bandwidth for both vertical x- and y-polarized wave incidence encompasses the entire in-band and partially out-band bandwidth of the antenna's operating bandwidth, demonstrating that the metasurface antenna exhibits RCS reduction both in-band and out-of-band.

[0052] The metasurface antenna disclosed in the present invention is a new type of antenna that has the characteristics of broadband left-handed circularly polarized radiation, in-band and out-of-band RCS reduction, low profile, and simple design. It has potential applications in future stealth communication platforms.

[0053] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section, characterized in that: include: The upper structure has a metasurface and the lower structure has a feed network, and the upper structure and the lower structure are bonded together by an adhesive layer composed of a middle layer of RO4450F semi-cured sheet.

2. The broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to claim 1, wherein: The upper structure includes: a metasurface metal patch, a first dielectric substrate, and a metal floor connected from top to bottom; 16 unit structures are arranged into 4×4 units to form a metasurface, and the metal patches of each unit include: a C-shaped metal patch, a circular metal patch, and an L-shaped metal patch, and the C-shaped metal patch, the circular metal patch, and the L-shaped metal patch are not connected to each other; the short-circuit needle connects the circular metal patch and the metal floor, and the feeding probe connects the circular metal patch and the feeding network.

3. The broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to claim 2, wherein: The lower structure includes: a second dielectric substrate, on which a 1:16 broadband sequential rotation feeding network is provided; the feeding network includes: a 180-degree phase shifter, a first 90-degree phase shifter, a second 90-degree phase shifter, a first Wilkinson power divider, a second Wilkinson power divider, a third Wilkinson power divider, eight T-shaped power dividers and a microstrip transmission line; wherein the feeding network is connected to the input and output ends of the external signal through the microstrip transmission line, and the microstrip transmission line is connected to the first Wilkinson power divider; the first Wilkinson power divider is connected to the 180-degree phase shifter and the 180-degree reference divider corresponding to the 180-degree phase shifter through two mirror-symmetrical curved microstrip lines. The 180-degree phase shifter and the 180-degree reference microstrip line are connected to the second Wilkinson power divider and the third Wilkinson power divider respectively; the second Wilkinson power divider is connected to the first 90-degree phase shifter and the first 90-degree reference microstrip line corresponding to the first 90-degree phase shifter; the first 90-degree phase shifter and the first 90-degree reference microstrip line are connected to four T-shaped power dividers respectively; the third Wilkinson power divider is connected to the second 90-degree phase shifter and the second 90-degree reference microstrip line corresponding to the second 90-degree phase shifter, and the second 90-degree phase shifter and the second 90-degree reference microstrip line are connected to four T-shaped power dividers respectively.

4. The broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to claim 2, wherein: The first dielectric substrate is an F4BM265 dielectric substrate with h1 = 3 mm.

5. The broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to claim 2, wherein: The second dielectric substrate is an F4BM265 dielectric substrate with h3=0.1 mm.

6. The broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to claim 2, wherein: The adhesive layer connecting the first dielectric substrate and the second dielectric substrate is a RO4450F prepreg with a thickness of h2 = 0.2 mm.

7. The broadband circularly polarized metasurface antenna with reduced in-band and out-of-band radar cross-section according to claim 5, wherein: The thickness of the C-shaped metal patch, the circular metal patch, and the L-shaped metal patch are all 0.018 mm, and all metal materials are copper.

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