Anisotropic metasurface-based broadband low-RCS circularly polarized antenna array design method

Abstract

The invention discloses a broadband low-RCS (radar cross section) circularly polarized array antenna design method based on an anisotropic metasurface, which comprises the following steps of: designing an anisotropic metasurface unit 1 which has a reflection phase difference of 180 degrees + / -30 degrees to x-polarized and y-polarized incident waves in a required frequency band; the meta-structure surface unit 1 obtained in the step 1 is rotated by 90 degrees around the center of the meta-structure surface unit 1 to obtain a meta-structure surface unit 2, and the unit 1 and the unit 2 are orthogonally arranged to form a classic chessboard type broadband low RCS meta-structure surface; and a probe feed and a gap metal patch are introduced into the broadband low-RCS metasurface obtained in the step 2, and the broadband low-RCS circularly polarized array antenna is formed by controlling the feed amplitude and the feed phase of the area where the unit 1 and the unit 2 are located. According to the design method provided by the invention, the design of the broadband low-RCS circularly polarized array antenna with both radiation and scattering performance can be realized by only one unit structure, the design complexity of the broadband low-RCS circularly polarized array antenna can be greatly reduced, the design efficiency is improved, and the provided array antenna is compact in structure, low in cost, easy to process and wide in application prospect.

Description

Technical Field

[0001] The present invention relates to antenna design technology, and more specifically to a method for designing an array antenna with both radiation and scattering performances quickly by using a metasurface, and more specifically to a method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface. Background Art

[0002] Compared with linearly polarized antennas, circularly polarized antennas have the advantages of flexible receiving radiation, anti-multipath interference, improved multipath distortion and polarization mismatch, etc., and are widely used in satellite communications, aerospace, global positioning and radar systems. Array antennas have performance advantages that single antennas do not have, such as beam shaping, beam scanning and high gain, and are widely used in wireless systems such as communications, radar and navigation. However, the strong scattering problem of the antenna system has become a bottleneck restricting the improvement of the overall stealth performance of the platform. In addition, the rapid development of modern communication and radar technology has put forward higher and higher requirements for antenna systems, such as widening the working bandwidth. Therefore, the design of broadband low RCS circularly polarized array antennas is of great significance to the field of wireless communications. In recent years, electromagnetic metasurfaces have emerged in the field of antenna stealth with their advantages of low profile, light weight, easy conformality and low cost. Through the reasonable design of functional unit structure and spatial arrangement sequence, it can realize flexible control of electromagnetic wave amplitude, phase and polarization. In traditional low RCS antenna design, electromagnetic metasurfaces are usually regarded as a special scatterer. Low RCS is achieved by loading electromagnetic metasurfaces as auxiliary structures on antennas, which undoubtedly increases the cost and complexity of antenna design. In addition, for array antennas, how to load electromagnetic metasurfaces within limited array element spacing and achieve broadband RCS reduction of array antennas without affecting the radiation performance of array antennas has become a problem that plagues antenna designers. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention proposes a broadband low RCS circularly polarized antenna array design method based on anisotropic metasurface, comprising the following steps:

[0004] Step 1, designing the anisotropic first metasurface unit 100 so that it has a reflection phase difference of 180°±30° for x-polarized and y-polarized incident waves within a required frequency band;

[0005] The unit 100 includes, from top to bottom, a metal patch 1, a first dielectric substrate 2, a second dielectric substrate 3, a third dielectric substrate 4, a fourth dielectric substrate 5, and a metal floor 6;

[0006] The first dielectric substrate 2, the second dielectric substrate 3, the third dielectric substrate 4, and the fourth dielectric substrate 5 are all rectangular parallelepiped plates, and their projections on the horizontal plane overlap, and two adjacent dielectric substrates are in close contact; wherein, the first dielectric substrate 2 and the third dielectric substrate 4 are thin plates, and the second dielectric substrate 3 and the fourth dielectric substrate 5 are thick plates; the upper and lower surfaces of the first dielectric substrate 2, the second dielectric substrate 3, the third dielectric substrate 4, and the fourth dielectric substrate 5 are all square;

[0007] Taking the center of the upper surface of the first dielectric substrate 2 as the coordinate origin, a first spatial rectangular coordinate system is established, with the positive direction of the x-axis perpendicular to the paper plane outward, the positive direction of the y-axis horizontally to the right, and the positive direction of the z-axis vertically upward;

[0008] The metal patch 1 is a rectangular thin sheet; the metal patch 1 is printed on the first dielectric substrate 2, and the center of the metal patch 1 coincides with the projection of the center of the upper surface of the first dielectric substrate 2 on the horizontal plane; the four sides of the metal patch 1 are respectively parallel to the four sides of the upper surface of the first dielectric substrate 2 and keep a certain distance;

[0009] A metal floor 6 is attached below the fourth dielectric substrate 5, and the projections of the metal floor 6 and the fourth dielectric substrate 5 on the horizontal plane completely overlap;

[0010] Step 2, horizontally rotating the unit 100 obtained in step 1 by 90° around the center of its upper surface to obtain a second metasurface unit 200, hereinafter referred to as "the second unit 200", and arranging the first unit 100 and the second unit 200 in an orthogonal chessboard to form a chessboard-type broadband low RCS metasurface;

[0011] The chessboard-type broadband low RCS metasurface, hereinafter referred to as "metasurface", is a x The first region 10 and N x The second regions 20 are arranged orthogonally in a chessboard pattern, that is, N x ×N x Array, where N x is a positive even number; the first region 10 is composed of M x ×M x The first units 100 are closely arranged, and the second area 20 is composed of M x ×M x The second units 200 are closely arranged to form M x is a natural number greater than or equal to 3;

[0012] Step 3, introducing a probe metal feed 8, a slot metal patch 7 and a slot metal patch 9 into the broadband low RCS metasurface obtained in step 2, and forming a broadband low RCS circularly polarized array antenna by controlling the feeding amplitude and feeding phase of the first area 10 and the second area 20;

[0013] The broadband low RCS circularly polarized array antenna is formed as follows:

[0014] The gap metal patch 7 and the gap metal patch 9 are printed on the upper surface of the entire third dielectric substrate 4 in the first area 10 and the second area 20 respectively, that is, each area corresponds to a gap metal patch 7 or a gap metal patch 9; the gap metal patch 7 and the gap metal patch 9 are both composed of a square patch, four L-shaped patches and a transmission line, and the gap metal patch 7 is horizontally rotated 90° counterclockwise around the center of its upper surface to obtain the gap metal patch 9;

[0015] With the center of the upper surface of the third dielectric substrate 4 of the first region 10 as the coordinate origin, a second spatial rectangular coordinate system is established, with the positive direction of the x′ axis perpendicular to the paper surface and the positive direction of the y′ axis to the right horizontally, and the positive direction of the z′ axis upward vertically;

[0016] For the gap metal patch 7, the center of the square patch coincides with the projection of the coordinate origin o′ of the first region 10 on the horizontal plane; a cross gap is opened in the center of the square patch, and the gap of the cross gap along the x′ direction is extended toward the positive and negative semi-axis of x′, but the two ends are kept at a distance from the corresponding boundaries of the first region 10; the gap of the cross gap along the y′ direction is extended toward the positive and negative semi-axis of y′, but the two ends are kept at a small distance from the corresponding boundaries of the first region 10; four L-shaped patches extend outward from the four corners of the square patch, first extending perpendicularly to the starting edge to form a forearm, then bending 90 degrees to the right, and continuing to extend to form a rear arm, and the end of the extended rear arm is kept at a distance from the corresponding boundary of the first region 10, and the distance is determined according to the optimization result;

[0017] For the slotted metal patch 7, the transmission line is loaded forward close to the front edge of the square patch and a point to the left of the cross slot in the x′ direction, but maintains a spacing from the front L-shaped patch;

[0018] The cylindrical feeding metal probe 8 of the coaxial cable penetrates the third dielectric substrate 4 and the fourth dielectric substrate 5 from bottom to top, and is connected to the slot metal patch 7 on the x'o'y' plane; the connection position of the feeding metal probe and the slot metal patch 7 is obtained according to optimization.

[0019] In the first step of one embodiment of the present invention:

[0020] Metal patch 1 patch length l p In the range of 8 to 13 mm, the width w p The first dielectric substrate 2 and the third dielectric substrate 4 have a side length of 13 to 16 mm and a thickness of 0.04 to 0.2 mm; the second dielectric substrate 3 and the fourth dielectric substrate 5 have a side length of 13 to 16 mm and a thickness of 1.0 to 3.0 mm.

[0021] In the first step of a specific embodiment of the present invention:

[0022] Metal patch 1 patch length l p 12.6mm, width w p The first dielectric substrate 2 and the third dielectric substrate 4 have a side length of 13 mm, a thickness of 0.075 mm, and a dielectric constant in the range of 1.0 to 4.0; the second dielectric substrate 3 and the fourth dielectric substrate 5 have a side length of 13 mm, a thickness of 1.5 mm, and a dielectric constant in the range of 2.0 to 4.5.

[0023] In the second step of another embodiment of the present invention: N x 、N y Both are equal to 2, M x 、M y are both equal to 4; the positions of the first unit 100 and the second unit 200 can be interchanged.

[0024] In the third step of yet another embodiment of the present invention:

[0025] The side length w of the square patch is in the range of 6 to 18 mm; the length l of the cross gap along the x-axis s In the range of 6 to 14 mm, the width w s In the range of 0.2 to 2.6 mm, along the y-axis length l s1 In the range of 6 to 14 mm, the width w s1 In the range of 0.2 to 2.6 mm; the lengths l and ll of the front and rear arms of the L-shaped patch are in the range of 6 to 20 mm, and the width s is in the range of 1 to 4 mm; the length l of the transmission line along the x-axis f In the range of 3 to 8 mm; the distance between the probe center and the front edge of the transmission line is in the range of 1.2 to 4.4 mm.

[0026] In the third step of another specific embodiment of the present invention:

[0027] The side length w of the square patch is 14.2 mm; the length of the cross gap along the x-axis is l s 13.8mm, width w s 0.7mm, length along the y-axis l s1 9mm, width w s1 2mm; the lengths l and ll of the front and rear arms of the L-shaped patch are 8.7mm and 15mm respectively, and the width s is 2.3mm; the length l of the transmission line along the x-axis f 5.1mm, width w f In the range of 2.2 to 4.5 mm; the distance between the center of the probe and the front edge of the transmission line is 4.2 mm.

[0028] In the third step of another specific embodiment of the present invention:

[0029] The first area 10 is set as the upper left area, the second area 20 is set as the upper right area, the second area 20 is set as the lower left area, and the first area 10 is set as the lower right area. The excitation amplitudes of the four feeding ports of these four areas are equal, and the phases are 0°, 90°, 0°, and 90° respectively; a 2×2 broadband low RCS circularly polarized array antenna is realized.

[0030] The advantages of the present invention are:

[0031] 1. Provide a broadband low RCS circularly polarized array antenna based on anisotropic metasurface design, which can achieve broadband low RCS circularly polarized array antenna design with both radiation and scattering performance with only one unit structure. By utilizing the anisotropy of the anisotropic unit structure itself, for the incident wave with orthogonal polarization, there is a phase difference of 180°±30° in the reflection phase within the required frequency band, thereby achieving RCS reduction, and at the same time, combining appropriate feeding technology to achieve broadband circularly polarized radiation;

[0032] 2. The present invention can greatly reduce the complexity of broadband low RCS circularly polarized array antenna design and improve design efficiency. In the future, with the increasing advancement of electromagnetic metasurface technology, circularly polarized array antennas with better performance can be designed by referring to this design idea;

[0033] 3. The broadband low RCS circularly polarized array antenna proposed in the present invention has a compact structure, low cost, easy processing, and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The design method of the present invention;

[0035] Figure 2 is a schematic diagram of the structure of the anisotropic metasurface unit 1 of the present invention, wherein Figure 2 (a) is a top view, Figure 2 (b) is a front view;

[0036] Figure 3 for Figure 2 The reflection phase difference curve diagram of the anisotropic metasurface unit 1 formed into an infinite periodic array under vertical irradiation of x-polarized and y-polarized plane waves;

[0037] Figure 4 This is a schematic diagram of the classic chessboard-style broadband low RCS metasurface structure of the present invention, where Figure 4 (a) is a top view, Figure 4 (b) is a front view;

[0038] Figure 5 for Figure 4The single-station RCS comparison curves of the classic chessboard-type broadband low RCS metasurface and the metal plate of the same size under vertical illumination of x-polarized and y-polarized plane waves are shown;

[0039] Figure 6 Schematic diagram of the broadband low RCS circularly polarized array antenna structure of the present invention, wherein Figure 6 (a) is a top view of the gap metal patch layer. Figure 6 (b) is a front view of the array antenna of the present invention;

[0040] Figure 7 for Figure 6 The impedance matching curve of broadband low RCS circularly polarized array antenna is shown;

[0041] Figure 8 for Figure 6 The axial ratio curve of the broadband low RCS circularly polarized array antenna is shown;

[0042] Fig. 9 for Figure 6 The broadband low RCS circularly polarized array antenna gain curve is shown;

[0043] Fig.10 for Figure 6 The single-station RCS comparison curve of the broadband low RCS circularly polarized array antenna and the metal plate of the same size under vertical irradiation of x-polarized and y-polarized plane waves is shown;

[0044] Reference numerals:

[0045] 1 metal patch; 2 dielectric substrate; 3 dielectric substrate; 4 dielectric substrate; 5 dielectric substrate; 6 metal floor; 7 gap metal patch; 8 feeding metal probe; 9 gap metal patch; 10 first area; 20 second area; 100 first metasurface unit; 200 second metasurface unit. DETAILED DESCRIPTION

[0046] The broadband low RCS circularly polarized array antenna design method based on anisotropic metasurface proposed by the present invention is specifically explained by describing an embodiment in detail, and an example of the embodiment is shown in the accompanying drawings.

[0047] The present invention is described below with reference to the accompanying drawings.

[0048] like Figure 1 As shown, the design method of broadband low RCS circularly polarized array antenna based on anisotropic metasurface includes the following steps:

[0049] Step 1, designing the anisotropic first metasurface unit 100 so that it has a reflection phase difference of 180°±30° for x-polarized and y-polarized incident waves within a required frequency band;

[0050] The first metasurface unit 100 (hereinafter referred to as the “first unit 100”) is finally determined as follows: Figure 2 As shown, Figure 2 (a) is a top view, Figure 2 (b) is a front view. The unit 100 includes a metal patch 1, a first dielectric substrate 2, a second dielectric substrate 3, a third dielectric substrate 4, a fourth dielectric substrate 5, and a metal floor 6 from top to bottom.

[0051] The first dielectric substrate 2, the second dielectric substrate 3, the third dielectric substrate 4, and the fourth dielectric substrate 5 are all rectangular parallelepiped plates, their projections on the horizontal plane overlap, and two adjacent dielectric substrates are in close contact; among them, the first dielectric substrate 2 and the third dielectric substrate 4 are thin plates, and the second dielectric substrate 3 and the fourth dielectric substrate 5 are relatively thick plates.

[0052] In a specific embodiment of the present invention, the upper and lower surfaces of the first dielectric substrate 2 , the second dielectric substrate 3 , the third dielectric substrate 4 , and the fourth dielectric substrate 5 are all square.

[0053] Taking the center of the upper surface of the first dielectric substrate 2 as the coordinate origin, a first spatial rectangular coordinate system is established, such as Figure 2 As shown, perpendicular to the paper surface and outward is the positive direction of the x-axis, horizontally to the right is the positive direction of the y-axis, and vertically upward is the positive direction of the z-axis.

[0054] The metal patch 1 is a rectangular thin sheet; the metal patch 1 is printed on the first dielectric substrate 2, and the center of the metal patch 1 coincides with the projection of the center of the upper surface of the first dielectric substrate 2 on the horizontal plane; the four sides of the metal patch 1 are respectively parallel to the four sides of the upper surface of the first dielectric substrate 2 and maintain a certain distance.

[0055] A metal floor 6 is attached below the fourth dielectric substrate 5, and the projections of the metal floor 6 and the fourth dielectric substrate 5 on the horizontal plane completely overlap;

[0056] In one embodiment of the present invention, the metal patch 1 is a rectangular patch with a patch length of l p In the range of 8 to 13 mm, the preferred value is 12.6 mm, and the width w pThe first dielectric substrate 2, the second dielectric substrate 3, the third dielectric substrate 4, and the fourth dielectric substrate 5 have upper and lower surfaces that are all square, wherein the side length of the first dielectric substrate 2 and the third dielectric substrate 4 is in the range of 13 to 16 mm, preferably 13 mm, the thickness is in the range of 0.04 to 0.2 mm, preferably 0.075 mm, and the dielectric constant is in the range of 1.0 to 4.0, preferably 1.06. The second dielectric substrate 3 and the fourth dielectric substrate 5 have side lengths in the range of 13 to 16 mm, preferably 13 mm, the thickness is in the range of 1.0 to 3.0 mm, preferably 1.5 mm, and the dielectric constant is in the range of 2.0 to 4.5, preferably 4.4.

[0057] Figure 3 After the units 100 with the preferred value are arranged closely horizontally along the xoy plane to form an infinite periodic array, the reflection phase difference curves under vertical irradiation of x-polarized and y-polarized plane waves show that in the operating frequency band of 6.16 to 11.36 GHz, the reflection phase difference is almost in the range of 180°±30°.

[0058] Step 2, horizontally rotate the unit 100 obtained in step 1 by 90° around the center of its upper surface to obtain a second metasurface unit 200 (hereinafter referred to as "the second unit 200"), and arrange the first unit 100 and the second unit 200 according to an orthogonal chessboard. At this time, the first unit 100 and the second unit 200 are taken as a finite period array, and the array is a square array, forming a classic chessboard-style broadband low RCS metasurface.

[0059] Figure 4 Schematic diagram of the structure of the classic chessboard-type broadband low RCS metasurface (hereinafter referred to as “the metasurface of the present invention”) proposed in an embodiment of the present invention. The metasurface of the present invention is composed of N x The first region 10 and N x The second regions 20 are arranged orthogonally in a chessboard pattern, that is, N x ×N x Array, where N x is a positive even number. The first region 10 is composed of M x ×M x The first units 100 are closely arranged, and the second area 20 is composed of M x ×M x The second units 200 are closely arranged to form M x is a natural number greater than or equal to 3. In a specific embodiment of the present invention, N x 、N y Both are equal to 2, M x 、M y are equal to 4, such as Figure 4The positions of the first unit 100 and the second unit 200 can be interchanged.

[0060] Figure 5 for Figure 4 The single-station RCS comparison curves of the classic chessboard-like broadband low RCS metasurface and the metal plate of the same size under vertical irradiation of x-polarized and y-polarized plane waves are shown. It can be seen that the metasurface of the present invention has an RCS reduction effect in the wide frequency band range of 6.25 to 10.5 GHz under both polarizations.

[0061] Step 3, introducing a probe feed and a slot metal patch into the broadband low RCS metasurface obtained in step 2, and forming a broadband low RCS circularly polarized array antenna by controlling the feeding amplitude and feeding phase of the first area 10 and the second area 20;

[0062] Figure 6 Schematic diagram of the structure of a broadband low RCS circularly polarized array antenna (hereinafter referred to as “array antenna of the present invention”) proposed in an embodiment of the present invention. Figure 6 (a) is a top view of the gap metal patch layer. Figure 6 (b) is a front view of the array antenna of the present invention. Figure 4 A feeding metal probe 8 is introduced on the basis of the metasurface of the present invention, and the metasurface unit is excited by coupling through the slot metal patch 7 and the slot metal patch 9. At the same time, circularly polarized radiation is formed by controlling the amplitude and phase of the feeding port of the first area 10 and the second area 20.

[0063] Specifically, the gap metal patch 7 and the gap metal patch 9 are printed on the upper surface of the entire third dielectric substrate 4 in the first area 10 and the second area 20, respectively, that is, each area corresponds to a gap metal patch 7 or a gap metal patch 9. The gap metal patch 7 and the gap metal patch 9 are both composed of a square patch, four L-shaped patches and a transmission line. The gap metal patch 7 is horizontally rotated 90° counterclockwise around the center of its upper surface to obtain the gap metal patch 9, as shown in FIG. Figure 6 (a) shown.

[0064] A second spatial rectangular coordinate system is established with the center of the upper surface of the third dielectric substrate 4 of the first region 10 as the coordinate origin, with the positive direction of the x′ axis perpendicular to the paper surface and outward, the positive direction of the y′ axis horizontally to the right, and the positive direction of the z′ axis vertically upward.

[0065] like Figure 6As shown in (a), for the gap metal patch 7, the center of the square patch coincides with the projection of the coordinate origin o′ of the first region 10 on the horizontal plane. A cross gap is opened in the center of the square patch. The gap of the cross gap along the x′ direction extends toward the positive and negative semi-axis of x′, but the two ends maintain a certain distance from the corresponding boundaries of the first region 10; the gap of the cross gap along the y′ direction extends toward the positive and negative semi-axis of y′, but the two ends maintain a small distance from the corresponding boundaries of the first region 10. Four L-shaped patches extend outward from the four corners of the square patch, first extending perpendicularly to the starting edge to form a forearm, and then bending 90 degrees to the right after reaching a certain length, and continue to extend to form a rear arm. The end of the extended rear arm maintains a certain distance from the corresponding boundary of the first region 10, and the distance is determined according to the optimization result.

[0066] For the slot metal patch 7, the transmission line is closely attached to the front edge of the square patch and loaded forward at a point on the left side of the cross slot in the x′ direction, but keeps a certain distance from the front L-shaped patch.

[0067] The cylindrical feeding metal probe 8 of the coaxial cable penetrates the third dielectric substrate 4 and the fourth dielectric substrate 5 from bottom to top, and is connected to the slot metal patch 7 on the x'o'y' plane. The connection position of the feeding metal probe and the slot metal patch 7 is obtained according to optimization, and the position in this example is explained in the next paragraph. The feeding metal probe 8 transmits energy to the slot metal patch 7, and then couples to the top chessboard metasurface through the cross slot and radiates out.

[0068] The side length w of the square patch is in the range of 6 to 18 mm, and the preferred value is 14.2 mm. The length l of the cross gap along the x-axis s In the range of 6 to 14 mm, the preferred value is 13.8 mm, and the width w s In the range of 0.2 to 2.6 mm, the preferred value is 0.7 mm, and the length along the y axis is l s1 In the range of 6 to 14 mm, the preferred value is 9 mm, and the width w s1 The length l and l of the two arms of the L-shaped patch are in the range of 6 to 20 mm, and the preferred values ​​are 8.7 mm and 15 mm respectively. The width s is in the range of 1 to 4 mm, and the preferred value is 2.3 mm. The length l of the transmission line along the x-axis f In the range of 3 to 8 mm, the preferred value is 5.1 mm, and the width w fIn the range of 2.2 to 4.5 mm. The distance between the center of the probe and the front edge of the transmission line is in the range of 1.2 to 4.4 mm, and the preferred value is 4.2 mm. The excitation amplitudes of the four feeding ports of the first area 10 (upper left), the second area 20 (upper right), the second area 20 (lower left), and the first area 10 (lower right) are set to be equal, and the phases are 0°, 90°, 0°, and 90° respectively. So far, a 2×2 broadband low RCS circularly polarized array antenna has been realized using the design method of the present invention.

[0069] Figure 7 , Figure 8 and Fig. 9 They are the impedance matching curve, axial ratio curve and normal gain curve of the array antenna of the present invention respectively. It can be seen that the impedance bandwidth of the array antenna of the present invention is 5.89-9 GHz (relative bandwidth 41.77%), the axial ratio bandwidth is 4.88-7.99 GHz (relative bandwidth 48.33%), the 3dB gain bandwidth is 5.4-7.07 GHz, 7.5-7.95 GHz, and within the axial ratio bandwidth, the main polarization gain and the cross-polarization gain in the normal direction of the array antenna of the present invention differ by more than 15 dB. Fig.10 The single-station RCS comparison curves of the array antenna of the present invention and the metal plate of the same size under vertical irradiation of x-polarized and y-polarized plane waves are shown. It can be seen that in the wide frequency band range of 5 to 15 GHz, the array antenna of the present invention has obvious RCS reduction effect under both polarizations.

Claims

1. A broadband low RCS circularly polarized antenna array design method based on anisotropic metasurface, characterized in that: The following steps are involved: Step 1, designing an anisotropic first metasurface unit (100) so that it has a reflection phase difference of 180°±30° for x-polarized and y-polarized incident waves within a required frequency band; The unit (100) comprises, from top to bottom, a metal patch (1), a first dielectric substrate (2), a second dielectric substrate (3), a third dielectric substrate (4), a fourth dielectric substrate (5), and a metal floor (6); The first dielectric substrate (2), the second dielectric substrate (3), the third dielectric substrate (4), and the fourth dielectric substrate (5) are all rectangular parallelepiped plates, their projections on the horizontal plane overlap, and two adjacent dielectric substrates are in close contact; wherein the first dielectric substrate (2) and the third dielectric substrate (4) are thin plates, and the second dielectric substrate (3) and the fourth dielectric substrate (5) are thick plates; the upper and lower surfaces of the first dielectric substrate (2), the second dielectric substrate (3), the third dielectric substrate (4), and the fourth dielectric substrate (5) are all square; Taking the center of the upper surface of the first dielectric substrate (2) as the coordinate origin, a first spatial rectangular coordinate system is established, with the positive direction of the x-axis perpendicular to the paper surface and outwards, the positive direction of the y-axis horizontally to the right, and the positive direction of the z-axis vertically upwards; The metal patch (1) is a rectangular thin sheet; the metal patch (1) is printed on the first dielectric substrate (2), and the center of the metal patch (1) coincides with the projection of the center of the upper surface of the first dielectric substrate (2) on a horizontal plane; the four sides of the metal patch (1) are respectively parallel to the four sides of the upper surface of the first dielectric substrate (2) and maintain a certain distance; A metal floor (6) is attached below the fourth dielectric substrate (5), and projections of the metal floor (6) and the fourth dielectric substrate (5) on a horizontal plane completely overlap; Step 2, horizontally rotating the unit (100) obtained in step 1 by 90 degrees around the center of its upper surface to obtain a second metasurface unit (200), hereinafter referred to as "the second unit (200)", and arranging the first unit (100) and the second unit (200) in an orthogonal chessboard to form a chessboard-type broadband low RCS metasurface; The chessboard-type broadband low RCS metasurface, hereinafter referred to as "metasurface", is a x The first region (10) and N x The second regions (20) are arranged orthogonally in a chessboard, that is, N x ×N x Array, where N x is a positive even number; the first region (10) consists of M x ×M x The first units (100) are closely arranged, and the second region (20) is composed of M x ×M x The second units (200) are closely arranged, M x is a natural number greater than or equal to 3; Step 3, introducing a probe metal feed (8), a slot metal patch (7) and a slot metal patch (9) into the broadband low RCS metasurface obtained in step 2, and forming a broadband low RCS circularly polarized array antenna by controlling the feeding amplitude and feeding phase of the first region (10) and the second region (20); The broadband low RCS circularly polarized array antenna is formed as follows: The gap metal patch (7) and the gap metal patch (9) are respectively printed on the entire upper surface of the third dielectric substrate (4) in the first area (10) and the second area (20), that is, each area corresponds to a gap metal patch (7) or a gap metal patch (9); the gap metal patch (7) and the gap metal patch (9) are both composed of a square patch, four L-shaped patches and a transmission line, and the gap metal patch (7) is horizontally rotated 90 degrees counterclockwise around the center of its upper surface to obtain the gap metal patch (9); A second spatial rectangular coordinate system is established with the center of the upper surface of the entire third dielectric substrate (4) in the first region (10) as the coordinate origin, with the positive direction of the x′ axis perpendicular to the paper surface and outwards as the positive direction of the y′ axis, the positive direction of the y′ axis horizontally to the right as the positive direction of the z′ axis, and the positive direction of the z′ axis vertically upwards; For the gap metal patch (7), the center of the square patch coincides with the projection of the coordinate origin o′ of the first region (10) on the horizontal plane; a cross gap is opened in the center of the square patch, and the gap of the cross gap along the x′ direction is extended toward the positive and negative semi-axis of x′, but the two ends are kept at a distance from the corresponding boundaries of the first region (10); the gap of the cross gap along the y′ direction is extended toward the positive and negative semi-axis of y′, but the two ends are kept at a small distance from the corresponding boundaries of the first region (10); four L-shaped patches extend outward from the four corners of the square patch, first extending perpendicularly to the starting edge to form a front arm, then bending 90 degrees to the right and continuing to extend to form a rear arm, and the end of the extended rear arm is kept at a distance from the corresponding boundary of the first region (10), and the distance is determined according to the optimization result; For the slotted metal patch (7), the transmission line is closely attached to the front edge of the square patch and loaded forward at a point to the left of the cross slot in the x′ direction, but maintains a spacing from the L-shaped patch in front; The cylindrical feeding metal probe 8 of the coaxial cable penetrates the third dielectric substrate (4) and the fourth dielectric substrate (5) from bottom to top and is connected to the slot metal patch (7) on the x'o'y' plane; the connection position of the feeding metal probe and the slot metal patch (7) is obtained according to optimization.

2. The method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface according to claim 1, characterized in that: In the first step: Metal patch (1) Patch length l p In the range of 8 to 13 mm, the width w p The first dielectric substrate (2) and the third dielectric substrate (4) have side lengths in the range of 13 to 16 mm and thicknesses in the range of 0.04 to 0.2 mm; the second dielectric substrate (3) and the fourth dielectric substrate (5) have side lengths in the range of 13 to 16 mm and thicknesses in the range of 1.0 to 3.0 mm.

3. The method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface according to claim 2, characterized in that: In the first step: Metal patch (1) Patch length l p 12.6mm, width w p The first dielectric substrate (2) and the third dielectric substrate (4) have a side length of 13 mm and a thickness of 0.075 mm, and their dielectric constants are in the range of 1.0 to 4.0; the second dielectric substrate (3) and the fourth dielectric substrate (5) have a side length of 13 mm and a thickness of 1.5 mm, and their dielectric constants are in the range of 2.0 to 4.

5.

4. The method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface according to claim 1, characterized in that: In the second step: N x 、N y Both are equal to 2, M x 、M y are both equal to 4; the positions of the first unit (100) and the second unit (200) can be interchanged.

5. The method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface according to claim 1, characterized in that: In the third step: The side length w of the square patch is in the range of 6 to 18 mm; the length l of the cross gap along the x-axis s In the range of 6 to 14 mm, the width w s In the range of 0.2 to 2.6 mm, along the y-axis length l s1 In the range of 6 to 14 mm, the width w s1 In the range of 0.2 to 2.6 mm; the lengths l and ll of the front and rear arms of the L-shaped patch are in the range of 6 to 20 mm, and the width s is in the range of 1 to 4 mm; the length l of the transmission line along the x-axis f In the range of 3 to 8 mm; the distance between the probe center and the front edge of the transmission line is in the range of 1.2 to 4.4 mm.

6. The method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface according to claim 5, characterized in that: In the third step: The side length w of the square patch is 14.2 mm; the length of the cross gap along the x-axis is l s 13.8mm, width w s 0.7mm, length along the y-axis l s1 9mm, width w s1 2mm; the lengths l and ll of the front and rear arms of the L-shaped patch are 8.7mm and 15mm respectively, and the width s is 2.3mm; the length l of the transmission line along the x-axis f 5.1mm, width w f In the range of 2.2 to 4.5 mm; the distance between the center of the probe and the front edge of the transmission line is 4.2 mm.

7. The method for designing a broadband low RCS circularly polarized antenna array based on anisotropic metasurface according to claim 1, characterized in that: In the third step: The first area (10) is set as the upper left area, the second area (20) is set as the upper right area, the second area (20) is set as the lower left area, and the first area (10) is set as the lower right area. The excitation amplitudes of the four feeding ports of the four areas are equal, and the phases are 0°, 90°, 0°, and 90° respectively; a 2×2 broadband low RCS circularly polarized array antenna is realized.

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