A broadband low rcs array antenna loaded with fsr

Abstract

This invention discloses a broadband low RCS array antenna with FSR loading, wherein an absorbing layer is printed on the upper surface of a first dielectric substrate, a transmitting layer is printed on the middle and lower surfaces of a second dielectric substrate, a radiating layer is printed on the upper surface of a third dielectric substrate, and a metal base plate is printed on the lower surface of the third dielectric substrate; the second dielectric substrate comprises two dielectric substrates stacked together; the absorbing layer includes a metal square ring with four branches and lumped resistors loaded on the four sides of the metal square ring, wherein each branch is a metal rectangular ring with a bent metal strip connected to the apex of the metal square ring; the transmitting layer includes a pair of metal rings and a perforated metal plate, wherein the pair of metal rings are respectively placed on the upper and lower surfaces of the second dielectric substrate, and the perforated metal plate is placed in the middle of the second dielectric substrate; the radiating layer includes a microstrip antenna array and its feeding network loaded on the upper surface of the third dielectric substrate, and a metal base plate on the lower surface of the third dielectric substrate; the radiating layer is coaxially fed.

Description

Technical Field

[0001] This invention belongs to the field of microwave antenna technology, specifically a broadband low RCS array antenna with FSR loading, which can be used for radar cross section reduction. Background Technology

[0002] In recent years, due to the development of stealth and anti-stealth technologies, radar cross section (RCS) has become a key research focus. Antennas are the most important part of wireless communication systems. For normal communication, antennas must effectively radiate electromagnetic waves. Furthermore, for wireless communication platforms with low scattering characteristics, antennas must possess good scattering properties; low-RCS antennas are ideal for radio communication systems. Therefore, effectively controlling and reducing the antenna's RCS without affecting its normal radiation characteristics has become an urgent problem to solve. The antenna's scattering field includes mode scattering and structure scattering. Currently, the most commonly used methods for RCS reduction are reshaping techniques and the application of absorbing materials. Reshaping techniques reduce scattering by slotting or cutting away sections of the antenna structure with weak current. While this method lowers the RCS, it significantly impacts the antenna's radiation characteristics. Similarly, applying absorbing materials around the antenna not only significantly affects its radiation but also mostly absorbs electromagnetic waves in only one polarization direction, making it unsuitable for various complex electromagnetic environments. In addition, some literature has proposed reducing RCS by randomly arranging AMC (Artificial Magnetic Conductor) units or phase gradient units. However, this method is difficult to achieve broadband RCS reduction. Furthermore, although the RCS is reduced in the normal direction, it may increase in other directions. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the existing technology by proposing a broadband low RCS array antenna with FSR loading, so as to ensure normal antenna radiation while widening the absorption bandwidth and achieving good absorption effect in various complex electromagnetic environments.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A broadband low RCS array antenna with FSR loading includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, an absorbing layer, a transmitting layer, a radiating layer, and a metal substrate, wherein:

[0006] The absorbing layer is printed on the upper surface of the first dielectric substrate, the wave-transmitting layer is printed on the middle and lower surfaces of the second dielectric substrate, the radiating layer is printed on the upper surface of the third dielectric substrate, and the metal base plate is printed on the lower surface of the third dielectric substrate.

[0007] The second dielectric substrate comprises two dielectric substrates stacked together;

[0008] The absorbing layer includes a metal square ring with four branches and lumped resistors loaded on the four sides of the metal square ring, wherein each branch is a metal rectangular ring with a bent metal strip connected to the apex of the metal square ring.

[0009] The wave-transparent layer includes a pair of metal rings and a perforated metal plate, wherein the pair of metal rings are respectively placed on the upper surface of the first dielectric layer and the lower surface of the second dielectric layer in the second dielectric plate; the perforated metal plate is placed between the first dielectric layer and the second dielectric layer of the second dielectric plate.

[0010] The radiating layer includes a microstrip antenna array and its feeding network loaded on the upper surface of the third dielectric substrate, and a metal base plate on the lower surface of the third dielectric substrate; the radiating layer is fed by a coaxial line.

[0011] Furthermore, the first dielectric substrate has a relative permittivity of 3.5 and a thickness of 0.6 mm; the two dielectric substrates in the second dielectric substrate each have a relative permittivity of 2.65 and a thickness of 0.8 mm; and the third dielectric substrate has a relative permittivity of 2.2 and a thickness of 0.6 mm.

[0012] Furthermore, the two gaps between the first dielectric plate and the second dielectric plate, and between the second dielectric plate and the third dielectric plate, are both air cavities. The height of the air cavity between the lower surface of the first dielectric plate and the upper surface of the second dielectric plate is 6 mm, and the height of the air cavity between the lower surface of the second dielectric plate and the upper surface of the third dielectric plate is 20 mm.

[0013] Furthermore, each vertex of the metal square ring is connected to a structurally identical and symmetrical branch via a metal connecting strip. This branch is a rectangular metal ring with bent metal strips. The bent metal strips consist of eight metal strips of uniform width. The first metal strip is connected to the inner middle of one short side of the rectangular metal ring; the second metal strip is connected to the side end of the first metal strip; the third metal strip is connected to the side end of the second metal strip and has a gap between it and one long side of the rectangular metal ring; the fourth metal strip is connected to the side end of the third metal strip; and the fifth metal strip is connected to… There is a gap between the end side of the fourth metal strip and the other long side of the metal rectangular ring; the sixth metal strip is connected to the end side of the fifth metal strip, one end of the seventh metal strip is connected to the end side of the sixth metal strip, and the other end is connected to the middle of the side of the eighth metal strip, with a gap between the eighth metal strip and the other short side of the metal rectangular ring; wherein, the first, third, fifth, and seventh metal strips are parallel to the long side of the metal rectangular ring, and the second, fourth, sixth, and eighth metal strips are parallel to the short side of the metal rectangular ring.

[0014] Furthermore, the inner side length of the metal square ring is 1.8mm, the width of each side is 0.3mm, and four lumped resistors with a resistance of 120Ω are respectively loaded at the center of each side of the metal square ring. The length of the lumped resistor is 0.5mm and the width is 0.3mm.

[0015] The length of the metal connecting strip between the metal square ring and the metal rectangular ring is 0.85 mm. The outer length of the long side of the metal rectangular ring is 3.2 mm, and the outer width of the short side of the metal rectangular ring is 2.6 mm. The width of the long side, the short side, and each metal strip is 0.2 mm.

[0016] For the bent metal strips, the lengths are as follows: the first metal strip is 0.6 mm, the second metal strip is 0.8 mm, the third metal strip is 0.8 mm, the fourth metal strip is 1.6 mm, the fifth metal strip is 0.9 mm, the sixth metal strip is 0.75 mm, the seventh metal strip is 0.7 mm, and the eighth metal strip is 1.6 mm.

[0017] Furthermore, the inner diameter of the metal ring is 6mm, and the difference between the inner diameter and the outer diameter is 2.4mm; the diameter of the hole in the perforated metal plate is 5.6mm.

[0018] Furthermore, the FSR array above the 2×2 microstrip array antenna loaded on the radiating layer is composed of 7×7 absorbing layers and 7×7 transparent layers.

[0019] Furthermore, the microstrip antenna array in the radiating layer comprises four identical microstrip patch antennas, a feed network, and a metal substrate; the feed network includes a 1-to-4 power divider, wherein one end of the first segment is connected to a coaxial line, and the other end is connected to a second segment on each side; the end of each second segment is connected to a third segment, the end of each third segment is connected to a fourth segment on each side, the end of each fourth segment is connected to a fifth segment, the end of the fifth segment is connected to a sixth segment, and the end of the sixth segment is inserted into a matching slot; wherein the fifth segment is perpendicular to the sixth segment, the angle between the fourth and fifth segments is an obtuse angle, and the angle between the fourth and third segments is an acute angle.

[0020] Furthermore, the microstrip patch antenna has a length of 16mm and a width of 10.95mm; the matching slot on the microstrip patch antenna has a depth of 3mm and a width of 1.35mm; the first segment of the power divider has a length of 7.1mm and a width of 1.5mm, each second segment has a length of 6.3mm and a width of 0.45mm; the third segment has a length of 6.2mm and a width of 0.85mm; the fourth, fifth, and sixth segments all have a width of 0.45mm, the fourth segment has a length of 8.65mm, the fifth segment has a length of 7.45mm, and the sixth segment has a length of 5.83mm.

[0021] Compared with the prior art, the present invention has the following technical features:

[0022] 1. The absorbing layer designed in this invention adopts a metal square ring combined with lumped resistance, which combines ohmic loss and dielectric substrate loss to expand the bandwidth of the absorbing layer, realize the broadband absorption characteristics of the array antenna, and thus reduce the RCS of the array antenna.

[0023] 2. This invention achieves miniaturization of the absorbing unit by bending metal strips.

[0024] 3. By adopting a bandpass frequency selective surface structure, good transmittance characteristics with insertion loss below -1dB are achieved within the antenna's operating frequency band, ensuring the normal operation of the antenna.

[0025] 4. This invention adopts a centrally symmetrical structure, which can absorb electromagnetic waves in the main polarization and cross-polarization directions, and is suitable for a variety of complex electromagnetic environments. Attached Figure Description

[0026] Figure 1 This is an overall structure diagram of the antenna provided by the present invention;

[0027] Figure 2 This is a schematic diagram of the absorbing layer structure of the antenna of the present invention, wherein (a) is the overall structure of the absorbing layer and (b) is the local structure of the absorbing layer;

[0028] Figure 3 This is a schematic diagram of the bandpass FSS unit structure of the antenna of the present invention;

[0029] Figure 4 This is a schematic diagram of the overall FSR structure of the antenna of the present invention;

[0030] Figure 5 This is a schematic diagram of the microstrip array antenna structure of the antenna of the present invention, wherein (a) is the overall structure of the microstrip array antenna and (b) is a partial structure of the microstrip array antenna;

[0031] Figure 6 This is a comparison diagram of the S11 reflection coefficient amplitudes of the antenna of this invention and the reference antenna;

[0032] Figure 7 This is a comparison diagram of the radiation patterns of the antenna of this invention and the reference antenna at 8.8 GHz in the E-plane.

[0033] Figure 8 This is a comparison diagram of the H-plane radiation patterns of the antenna of this invention and the reference antenna at 8.8 GHz;

[0034] Figure 9 (a) and (b) are comparison diagrams of the radar cross section (RCS) of the antenna designed in this invention and the reference antenna, where (a) is the case of x-polarized incident wave and (b) is the case of y-polarized incident wave.

[0035] Explanation of the labels in the diagram: 1 First dielectric substrate, 2 Second dielectric substrate, 3 Third dielectric substrate, 4 Absorbing layer, 41 Metal square ring, 42 Lumped resistor, 43 Metal rectangular ring, 44 Metal connecting strip, 45 Bent metal strip, 451 to 458 are the first to eighth metal strips respectively, 5 Transparent layer, 51 Metal ring, 52 Hole-cut metal, 6 Radiation layer, 61 Microstrip patch antenna, 62 Feed network, 63 Matching slot, 64 Power divider, 641 to 646 are the first to sixth sections of the power divider respectively, 465 Coaxial cable, 7 Metal base plate. Detailed Implementation

[0036] A frequency selective radiator (FSR) combines a circuit analog absorber (CAA) with a traditional frequency selective surface (FSS), enabling excellent transmission of in-band waves while absorbing out-of-band waves, thereby reducing the multi-station RCS of the antenna. This invention combines a multi-resonant structured circuit analog absorber (CAA) with a traditional frequency selective surface (FSS) to achieve the characteristics of an integrated radiation and scattering antenna system. By loading the FSR structure provided by this invention onto a 2×2 array antenna, low RCS characteristics are achieved over a wide bandwidth (RCS reduction bandwidth of 2GHz to 16GHz) while ensuring normal antenna radiation.

[0037] Reference Figure 1This invention provides a broadband low RCS array antenna with FSR loading, comprising a first dielectric substrate 1, a second dielectric substrate 2, a third dielectric substrate 3, an absorbing layer 4, a transmitting layer 5, a radiating layer 6, and a metal substrate 7, wherein:

[0038] The absorbing layer 4 is printed on the upper surface of the first dielectric substrate 1, the wave-transmitting layer 5 is printed on the upper, middle and lower surfaces of the second dielectric substrate 2, the radiating layer 6 is printed on the upper surface of the third dielectric substrate 3, and the metal base plate 7 is printed on the lower surface of the third dielectric substrate 3.

[0039] The second dielectric substrate 2 comprises two dielectric substrates stacked together;

[0040] The absorbing layer 4 uses a metal square ring 41 with four branches and a lumped resistor 42 loaded on the four sides of the metal square ring 41. Each branch is a metal rectangular ring 43 with a bent metal strip connected to the top of the metal square ring, thereby forming a multi-resonant structure that combines multiple absorbing frequency bands and expands the absorbing bandwidth.

[0041] The wave-transparent layer 5 includes a pair of metal rings 51 and a perforated metal plate 52. The pair of metal rings 51 are respectively placed on the upper surface of the first dielectric layer and the lower surface of the second dielectric layer in the second dielectric plate 2. The perforated metal plate 52 is placed between the first dielectric layer and the second dielectric layer of the second dielectric plate 2, thereby forming a parallel resonant structure and realizing a wave-transparent band to effectively radiate the electromagnetic waves of the radiation layer.

[0042] The radiating layer 6 includes a microstrip antenna array and its feeding network 62 loaded on the upper surface of the third dielectric substrate 3, and a metal base plate 7 on the lower surface of the third dielectric substrate 3; the radiating layer 6 is fed by a coaxial line 65. The above structure is designed to achieve radiation and RCS suppression characteristics.

[0043] The specific structure of the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] See Figure 1 In one embodiment of the present invention, the first dielectric substrate 1 has a relative permittivity of 3.5 and a thickness of 0.6 mm, and an absorbing layer 5 is printed on the upper surface of the first dielectric substrate.

[0045] The second dielectric substrate 2 consists of two dielectric substrates stacked one on top of the other, both with a relative permittivity of 2.65 and a thickness of 0.8 mm.

[0046] The third dielectric substrate 3 has a relative permittivity of 2.2 and a thickness of 0.6 mm. A radiation layer 6 and a metal base plate 7 are placed on the upper and lower surfaces, respectively.

[0047] In this scheme, the two gaps between the first dielectric plate 1 and the second dielectric plate 2, and between the second dielectric plate 2 and the third dielectric plate 3 are both air cavities. The height h1 of the air cavity between the lower surface of the first dielectric plate 1 and the upper surface of the second dielectric plate 2 is 6 mm, and the height h2 of the air cavity between the lower surface of the second dielectric plate 2 and the upper surface of the third dielectric plate 3 is 20 mm.

[0048] Reference Figure 2 In this invention, the absorbing layer 4 is disposed on the first dielectric substrate 1, and a lumped resistor 42 is disposed on each side of the metal square ring 41. The period of the absorbing layer 4 is 12mm. In this embodiment, the inner side length L1 of the metal square ring 43 is 1.8mm, the width W1 of each side is 0.3mm, and four lumped resistors 42 with a resistance of 120Ω are respectively loaded at the center of each side of the metal square ring 41. The length L2 of the lumped resistor 42 is approximately 0.5mm, and the width is W1.

[0049] Each vertex of the metal square ring 41 is connected to a structurally identical and symmetrical branch via a metal connecting strip 44. This branch is a rectangular metal ring 43 with bent metal strips 45. The bent metal strips consist of eight metal strips of equal width. A first metal strip 451 is connected to the inner middle of one short side of the rectangular metal ring 43. A second metal strip 452 is connected to the side end of the first metal strip 451. A third metal strip 453 is connected to the side end of the second metal strip 452 and has a gap between it and one long side of the rectangular metal ring 43. A fourth metal strip 454 is connected to the side end of the third metal strip 453, and a fifth metal strip 455 is connected to the end of the fourth metal strip 454. There is a gap between the side of the fifth metal strip 455 and the other long side of the metal rectangular ring 43; the sixth metal strip 456 is connected to the side of the end of the fifth metal strip 455, one end of the seventh metal strip 457 is connected to the side of the end of the sixth metal strip 456, and the other end is connected to the middle of the side of the eighth metal strip 458, and there is a gap between the eighth metal strip 458 and the other short side of the metal rectangular ring 43; wherein, the first metal strip 451, the third metal strip 453, the fifth metal strip 455 and the seventh metal strip 457 are parallel to the long side of the metal rectangular ring 43, and the second metal strip 452, the fourth metal strip 454, the sixth metal strip 456 and the eighth metal strip 458 are parallel to the short side of the metal rectangular ring 43.

[0050] In one embodiment of the present invention, the length L3 of the metal connecting strip 44 between the metal square ring 43 and the metal rectangular ring 43 is 0.85 mm, the outer length L4 of the long side of the metal rectangular ring 43 is 3.2 mm, and the outer width W2 of the short side of the metal rectangular ring 43 is 2.6 mm; the width W3 of the long side, the short side, and each metal strip is 0.2 mm.

[0051] For the bent metal strip 45, in this embodiment, the length L5 of the first metal strip 451 is 0.6mm, the length L6 of the second metal strip 452 is 0.8mm, the length L7 of the third metal strip 453 is 0.8mm, the length L8 of the fourth metal strip 454 is 1.6mm, the length L9 of the fifth metal strip 455 is 0.9mm, the length L10 of the sixth metal strip 456 is 0.75mm, the length L11 of the seventh metal strip 457 is 0.7mm, and the length L12 of the eighth metal strip 458 is 1.6mm.

[0052] Reference Figure 3 In this invention, a bandpass FSS unit is composed of a second dielectric substrate 2 and a wave-transparent layer 5. The wave-transparent layer 5 is disposed on the second dielectric substrate 2 and includes a pair of metal rings 51 arranged concentrically on top and bottom and a perforated metal plate 52. The inner diameter d1 of the metal rings 51 is 6 mm, and the difference between the inner diameter and the outer diameter is 2.4 mm. The perforated metal plate 52 is placed between the two dielectric substrates, and the diameter d3 of the hole is 5.6 mm.

[0053] Reference Figure 4 In this invention, an FSR unit structure includes an absorbing layer 4 unit and a transmitting layer 5 unit. In addition, the FSR array above the 2×2 microstrip array antenna loaded on the radiating layer 6 is composed of 7×7 absorbing layer 4 units and 7×7 transmitting layer 5 units.

[0054] Reference Figure 5The microstrip antenna array in the radiating layer 6 of this invention comprises four identical microstrip patch antennas 61, a feed network 62, and a metal substrate 7. In this embodiment, the microstrip patch antenna 61 has a length L1 of 16 mm and a width W1 of 10.95 mm; the matching slot 63 on the microstrip patch antenna 61 has a depth L2 of 3 mm and a width W2 of 1.35 mm; the feed network 62 includes a 1-to-4 power divider 64, wherein the first segment 641 of the power divider 64 has a length L3 of 7.1 mm and a width W3 of 1.5 mm, wherein one end of the first segment 641 is connected to a coaxial line 65, and the other end is connected to a second segment 642 on each side; each second segment 642 has a length L4 of 6.3 mm and a width W4 of 0.45 mm ... A third segment 643 is connected to the end of segment 42. The length L5 of the third segment 643 is 6.2 mm and the width W5 is 0.85 mm. A fourth segment 644 is connected to each side of the end of each third segment 643. The end of each fourth segment 644 is connected to a fifth segment 645. The end of the fifth segment 645 is connected to a sixth segment 646. The end of the sixth segment 646 is inserted into the matching slot 63. The fifth segment 645 is perpendicular to the sixth segment 646. The angle between the fourth segment 644 and the fifth segment 645 is an obtuse angle, and the angle between the fourth segment 644 and the third segment 643 is an acute angle. The width W6 of the fourth segment 644, the fifth segment 645, and the sixth segment 646 is 0.45 mm, the length L6 is 8.65 mm, the length L7 is 7.45 mm, and the length L8 is 5.83 mm. The microstrip antenna array and the power divider 64 are placed on the upper surface of the third dielectric substrate 3, and the metal base plate 7 is placed on the lower surface of the third dielectric substrate 3. They are fed by a coaxial cable 65.

[0055] The technical effects of the embodiments of the present invention can be further illustrated by the following simulation experiments.

[0056] (1) Simulation conditions

[0057] The antenna of the invention described above was simulated using the commercial simulation software CST Studio Suite 2023.

[0058] (2) Simulation content

[0059] Simulation 1: The backlash loss of the reference antenna and the invented antenna was simulated and calculated using the commercial simulation software CST Studio Suite 2023. The results are as follows: Figure 6 As shown. From Figure 6 It can be seen that the impedance bandwidth of the invented antenna in the -10dB range is 8.6-8.85GHz, with a relative bandwidth of 2.8%, while the impedance bandwidth of the reference antenna in the -10dB range is 8.7-8.87GHz, with a relative bandwidth of 1.9%. Therefore, it can be seen that the impedance bandwidth of the invented antenna in the -10dB range is wider than that of the reference antenna.

[0060] Simulation 2: The E-plane radiation patterns of the reference antenna and the invented antenna were simulated and calculated using the commercial simulation software CST Studio Suite 2023. The results are as follows: Figure 7 As shown. From Figure 7 It can be seen that the gain of the antenna of this invention is increased by about 2.5dB compared with the reference antenna, indicating that the antenna of this invention has good radiation performance.

[0061] Simulation 3: The H-plane radiation patterns of the reference antenna and the invented antenna were simulated and calculated using the commercial simulation software CST Studio Suite 2023. The results are as follows: Figure 8 As shown. From Figure 8 It can be seen that the gain of the antenna of this invention is increased by about 2.4 dB compared with the reference antenna, indicating that the antenna of this invention has good radiation performance.

[0062] Simulation 4: Using the commercial simulation software CST Studio Suite 2023, the monostatic radar cross sections of the reference antenna and the invented antenna under two different polarizations of incident wave illumination were simulated and calculated. The results are as follows: Figure 9 As shown. From Figure 9 As can be seen, compared with the reference antenna, the antenna of this invention can achieve out-of-band single-site RCS reduction in the range of 2GHz to 16GHz. In x-polarization, the maximum single-site RCS reduction is 43dB at 7.8GHz; in y-polarization, the maximum single-site RCS reduction is 35dB at 7.8GHz.

[0063] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A broadband low RCS array antenna with FSR loading, characterized in that, It includes a first dielectric substrate (1), a second dielectric substrate (2), a third dielectric substrate (3), an absorbing layer (4), a transparent layer (5), a radiating layer (6), and a metal base plate (7), wherein: The absorbing layer (4) is printed on the upper surface of the first dielectric plate (1), the wave-transmitting layer (5) is printed on the upper, middle and lower surfaces of the second dielectric plate (2), the radiating layer (6) is printed on the upper surface of the third dielectric plate (3), and the metal base plate (7) is printed on the lower surface of the third dielectric plate (3). The second dielectric substrate (2) comprises two dielectric substrates stacked together; The absorbing layer (4) includes a metal square ring (41) with four branches and a lumped resistor (42) loaded on the four sides of the metal square ring (41), wherein each branch is a metal rectangular ring (43) with a bent metal strip (45) connected to the apex of the metal square ring (41). The wave-transparent layer (5) includes a pair of metal rings (51) and a perforated metal plate (52), wherein the pair of metal rings (51) are respectively placed on the upper surface of the first dielectric layer and the lower surface of the second dielectric layer in the second dielectric plate (2); the perforated metal plate (52) is placed between the first dielectric layer and the second dielectric layer of the second dielectric plate (2); The radiating layer (6) includes a microstrip antenna array and its feeding network (62) loaded on the upper surface of the third dielectric substrate (3), and a metal base plate (7) on the lower surface of the third dielectric substrate (3); the radiating layer (6) is fed by a coaxial line (65).

2. The broadband low RCS array antenna with FSR loading according to claim 1, characterized in that, The first dielectric substrate (1) has a relative permittivity of 3.5 and a thickness of 0.6 mm; the two dielectric substrates in the second dielectric substrate (2) have a relative permittivity of 2.65 and a thickness of 0.8 mm; the third dielectric substrate (3) has a relative permittivity of 2.2 and a thickness of 0.6 mm.

3. The broadband low RCS array antenna with FSR loading according to claim 1, characterized in that, The two gaps between the first dielectric plate (1) and the second dielectric plate (2), and between the second dielectric plate (2) and the third dielectric plate (3) are both air cavities. The height of the air cavity between the lower surface of the first dielectric plate (1) and the upper surface of the second dielectric plate (2) is 6 mm, and the height of the air cavity between the lower surface of the second dielectric plate (2) and the upper surface of the third dielectric plate (3) is 20 mm.

4. The broadband low RCS array antenna with FSR loading according to claim 1, characterized in that, Each vertex of the metal square ring (41) is connected to a symmetrical branch with the same structure via a metal connecting strip (44). This branch is a rectangular metal ring (43) with a bent metal strip (45). The bent metal strip consists of eight metal strips of the same width. The first metal strip (451) is connected to the middle of the inner side of one short side of the rectangular metal ring (43). The second metal strip (452) is connected to the side end of the first metal strip (451). The third metal strip (453) is connected to the side end of the second metal strip (452) and has a gap between it and one long side of the rectangular metal ring (43). The fourth metal strip (454) is connected to the side end of the third metal strip (453). The fifth metal strip (455) is connected to the side end of the fourth metal strip (454). There is a gap between the metal rectangular ring (43) and the other long side; the sixth metal strip (456) is connected to the side of the end of the fifth metal strip (455), one end of the seventh metal strip (457) is connected to the side of the end of the sixth metal strip (456), and the other end is connected to the middle of the side of the eighth metal strip (458). There is a gap between the eighth metal strip (458) and the other short side of the metal rectangular ring (43); wherein, the first metal strip (451), the third metal strip (453), the fifth metal strip (455) and the seventh metal strip (457) are parallel to the long side of the metal rectangular ring (43), and the second metal strip (452), the fourth metal strip (454), the sixth metal strip (456) and the eighth metal strip (458) are parallel to the short side of the metal rectangular ring (43).

5. The broadband low RCS array antenna with FSR loading according to claim 4, characterized in that, The inner side length of the metal square ring (41) is 1.8 mm, the width of each side is 0.3 mm, and four lumped resistors (42) with a resistance of 120 Ω are respectively loaded at the center of each side of the metal square ring (41). The length of the lumped resistor (42) is 0.5 mm and the width is 0.3 mm. The length of the metal connecting strip (44) between the metal square ring (41) and the metal rectangular ring (43) is 0.85 mm, the outer length of the long side of the metal rectangular ring (43) is 3.2 mm, and the outer width of the short side of the metal rectangular ring (43) is 2.6 mm; the width of the long side, the short side, and each metal strip is 0.2 mm. For the bent metal strip (45), the length of the first metal strip (451) is 0.6 mm, the length of the second metal strip (452) is 0.8 mm, the length of the third metal strip (453) is 0.8 mm, the length of the fourth metal strip (454) is 1.6 mm, the length of the fifth metal strip (455) is 0.9 mm, the length of the sixth metal strip (456) is 0.75 mm, the length of the seventh metal strip (457) is 0.7 mm, and the length of the eighth metal strip (458) is 1.6 mm.

6. The broadband low RCS array antenna with FSR loading according to claim 1, characterized in that, The inner diameter of the metal ring (51) is 6 mm, and the difference between the inner diameter and the outer diameter is 2.4 mm; the diameter of the hole in the perforated metal plate (52) is 5.6 mm.

7. The broadband low RCS array antenna with FSR loading according to claim 1, characterized in that, The FSR array above the 2×2 microstrip array antenna loaded on the radiating layer (6) is composed of 7×7 absorbing layers (4) and 7×7 transparent layers (5).

8. The broadband low RCS array antenna with FSR loading according to claim 1, characterized in that, The microstrip antenna array in the radiating layer (6) includes four identical microstrip patch antennas (61), a feed network (62), and a metal base plate (7). The feed network (62) includes a 1-to-4 power divider (64), wherein one end of the first segment (641) is connected to a coaxial line (65), and the other end is connected to a second segment (642) on both sides. The end of each second segment (642) is connected to a third segment (643), the end of each third segment (643) is connected to a fourth segment (644) on both sides, the end of each fourth segment (644) is connected to a fifth segment (645), the end of the fifth segment (645) is connected to a sixth segment (646), and the end of the sixth segment (646) is inserted into a matching slot (63). The fifth segment (645) is perpendicular to the sixth segment (646), the angle between the fourth segment (644) and the fifth segment (645) is an obtuse angle, and the angle between the fourth segment (644) and the third segment (643) is an acute angle.

9. The broadband low RCS array antenna with FSR loading according to claim 8, characterized in that, The microstrip patch antenna (61) has a length of 16 mm and a width of 10.95 mm; the matching slot (63) on the microstrip patch antenna (61) has a depth of 3 mm and a width of 1.35 mm; the first segment (641) of the power divider (64) has a length of 7.1 mm and a width of 1.5 mm, each second segment (642) has a length of 6.3 mm and a width of 0.45 mm; the third segment (643) has a length of 6.2 mm and a width of 0.85 mm; the fourth segment (644), the fifth segment (645), and the sixth segment (646) all have a width of 0.45 mm, the fourth segment (644) has a length of 8.65 mm, the fifth segment (645) has a length of 7.45 mm, and the sixth segment (646) has a length of 5.83 mm.

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