Broadband low RCS array antenna loaded with FSR

Abstract

The invention discloses a broadband low RCS array antenna loaded with FSR. A wave absorbing layer is printed on the upper surface of a first dielectric plate, a wave transparent layer is printed on the upper, middle and lower surfaces of a second dielectric plate, a radiation layer is printed on the upper surface of a third dielectric plate, and a metal bottom plate is printed on the lower surface of the third dielectric plate; the second dielectric plate comprises two layers of dielectric plates which are stacked together; the wave absorbing layer comprises a metal square ring with four branches and lumped resistors loaded on the four sides of the metal square ring, and each branch is a metal rectangular ring which is connected to the vertex of the metal square ring and is provided with a bent metal strip; the wave-transparent layer comprises a pair of metal rings and a perforated metal plate, the pair of metal rings are placed on the upper surface and the lower surface of the second dielectric plate respectively, and the perforated metal plate is placed in the middle of the second dielectric plate; the radiation layer comprises a microstrip antenna array loaded on the upper surface of the third dielectric plate, a feed network of the microstrip antenna array, and a metal bottom plate on the lower surface of the third dielectric plate; and the radiation layer adopts coaxial line feed.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave antennas, and in particular relates to a broadband low RCS array antenna loaded with FSR, which can be used for radar cross section reduction. Background Art

[0002] In recent years, due to the development of stealth and anti-stealth technology, radar cross section (RCS) has become the focus of current research. The antenna is the most important part of the wireless communication system. In order to ensure the normal communication of the system, it is necessary to ensure that the antenna can effectively radiate electromagnetic waves. At the same time, for wireless communication platforms with low scattering characteristics, the antenna must have good scattering characteristics. Low RCS antennas are ideal for radio communication systems. Therefore, under the premise of not affecting the normal radiation characteristics of the antenna, effectively controlling and reducing the RCS of the antenna has become an urgent problem to be solved. The scattering field of the antenna includes mode scattering and structural scattering. The most commonly used RCS reduction methods are shaping technology and coating absorbing materials. The shaping technology is to reduce the scattering of the antenna by slotting or cutting off the part of the antenna structure with weaker current. Although this method reduces the RCS of the antenna, it has a greater impact on the radiation characteristics of the antenna; similarly, loading absorbing materials around the antenna will not only have a greater impact on the radiation of the antenna, but most of them can only absorb electromagnetic waves in one polarization direction, which is difficult to apply to a variety of complex electromagnetic environments. In addition, there are currently some literatures that use random arrangement of AMC (Artificial magnetic conductor) units or phase gradient units to reduce RCS. First of all, this method is difficult to achieve broadband RCS reduction; in addition, although the RCS in the normal direction is reduced, its RCS in other directions may be enhanced. Summary of the invention

[0003] The purpose of the present invention is to address the deficiencies in the above-mentioned prior art and to propose a broadband low RCS array antenna loaded with FSR, so as to ensure the normal radiation of the antenna while broadening the absorbing bandwidth, so as to achieve good absorbing effect in a variety of complex electromagnetic environments.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] A broadband low RCS array antenna loaded with FSR, comprising a first dielectric plate, a second dielectric plate, a third dielectric plate, a wave absorbing layer, a wave transmitting layer, a radiation layer and a metal bottom plate, wherein:

[0006] The wave absorbing layer is printed on the upper surface of the first dielectric plate, the wave transmitting layer is printed on the middle and lower surfaces of the second dielectric plate, the radiation layer is printed on the upper surface of the third dielectric plate, and the metal bottom plate is printed on the lower surface of the third dielectric plate;

[0007] The second dielectric plate comprises two dielectric plates stacked together;

[0008] The wave absorbing layer comprises a metal square ring with four branches and a lumped resistor loaded on four sides of the metal square ring, wherein each branch is a metal rectangular ring with a bent metal strip connected to the vertex of the metal square ring;

[0009] The wave-transmitting layer comprises a pair of metal rings and a holed 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 holed metal plate is placed between the first dielectric layer and the second dielectric layer of the second dielectric plate;

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

[0011] Furthermore, the relative dielectric constant of the first dielectric plate is 3.5, and the thickness is 0.6 mm; the relative dielectric constants of the two dielectric plates in the second dielectric plate are both 2.65, and the thicknesses are both 0.8 mm; the relative dielectric constant of the third dielectric plate is 2.2, and the thickness is 0.6 mm.

[0012] Furthermore, the two layers of 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, wherein 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 branch with the same structure and symmetry through a metal connecting strip on the outside, and the branch is a metal rectangular ring with a bent metal strip; wherein the bent metal strip is composed of eight metal strips of uniform width, wherein the first metal strip is connected to the inner middle of a short side of the metal rectangular ring, the second metal strip is connected to the side of the end of the first metal strip, the third metal strip is connected to the side of the end of the second metal strip and there is a gap between it and a long side of the metal rectangular ring; the fourth metal strip is connected to the side of the end of the third metal strip, and the fifth metal strip is connected to the side of the end of the third metal strip. There is a gap between the side surface of the end of the fourth metal strip and the other long side of the metal rectangular ring; the sixth metal strip is connected to the side surface of the end of the fifth metal strip, one end of the seventh metal strip is connected to the side surface of the end of the sixth metal strip, and the other end is connected to the middle of the side surface of the eighth metal strip, and there is a gap between the eighth metal strip and the other short side of the metal rectangular ring; wherein, the first metal strip, the third metal strip, the fifth metal strip and the seventh metal strip are parallel to the long side of the metal rectangular ring, and the second metal strip, the fourth metal strip, the sixth metal strip and the eighth metal strip are parallel to the short side of the metal rectangular ring.

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

[0015] The length of the metal connecting band 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, short side and each metal strip is 0.2 mm;

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

[0017] Furthermore, the inner diameter of the metal ring is 6 mm, and the difference between the inner diameter and the outer diameter is 2.4 mm; the diameter of the circular hole dug out on the holed metal plate is 5.6 mm.

[0018] Furthermore, the FSR array above the 2×2 microstrip array antenna loaded on the radiation layer is composed of 7×7 absorbing layers 4 and 7×7 wave-transmitting layers.

[0019] Furthermore, the microstrip antenna array in the radiation layer includes four identical microstrip patch antennas, a feeding network and a metal base plate; the feeding network includes a one-to-four equal-division power divider, wherein one end of the first segment is connected to the coaxial line, and the two sides of the other end are respectively connected to a second segment; the end of each second segment is connected to a third segment, the two sides of the end of each third segment are respectively connected to a fourth segment, 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 the matching slot; wherein the fifth segment is perpendicular to the sixth segment, the angle between the fourth segment and the fifth segment is an obtuse angle, and the angle between the fourth segment and the third segment is an acute angle.

[0020] Furthermore, the microstrip patch antenna is 16 mm long and 10.95 mm wide; the matching slot on the microstrip patch antenna is 3 mm deep and 1.35 mm wide; the first section of the power divider is 7.1 mm long and 1.5 mm wide, and each second section is 6.3 mm long and 0.45 mm wide; the third section is 6.2 mm long and 0.85 mm wide; the fourth, fifth and sixth sections are all 0.45 mm wide, the fourth section is 8.65 mm long, the fifth section is 7.45 mm long, and the sixth section is 5.83 mm long.

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

[0022] 1. The absorbing layer designed in the present invention adopts a metal square ring combined with a lumped resistor method, combines ohmic loss and dielectric substrate loss, expands the bandwidth of the absorbing layer, realizes the broadband absorbing characteristics of the array antenna, and thus reduces the RCS of the array antenna.

[0023] 2. The present invention adopts the method of bending metal strips to achieve the miniaturization of the absorbing unit.

[0024] 3. The bandpass frequency selective surface structure is adopted to achieve good wave transmission characteristics with insertion loss lower than -1dB within the working frequency band of the antenna, ensuring the normal operation of the antenna.

[0025] 4. The present invention adopts a central 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 2 Schematic diagram of the structure of the absorbing layer 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 It is a schematic diagram of the bandpass FSS unit structure of the antenna of the present invention;

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

[0030] Figure 5 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 the local structure of the microstrip array antenna;

[0031] Figure 6 is a comparison diagram of the S11 reflection coefficient amplitude of the antenna of the present invention and the reference antenna;

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

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

[0034] Fig. 9 (a) and (b) are comparison diagrams of radar cross-section (RCS) of the antenna designed according to the present invention and the reference antenna, wherein (a) is the case of x-polarized incident wave, and (b) is the case of y-polarized incident wave.

[0035] Explanation of the numbers in the figure: 1 the first dielectric plate, 2 the second dielectric plate, 3 the third dielectric plate, 4 the absorbing layer, 41 the metal square ring, 42 the lumped resistor, 43 the metal rectangular ring, 44 the metal connecting strip, 45 the bent metal strip, 451 to 458 are the first metal strip to the eighth metal strip respectively, 5 the transparent layer, 51 the metal ring, 52 the holed metal, 6 the radiation layer, 61 the microstrip patch antenna, 62 the feeding network, 63 the matching slot, 64 the power divider, 641 to 646 are the first section to the sixth section of the power divider respectively, 465 the coaxial line, 7 the metal bottom plate. DETAILED DESCRIPTION

[0036] FSR (Frequency selective rasorber) combines the circuit analog absorber (CAA) with the traditional frequency selective surface (FSS), which can absorb out-of-band waves while transmitting in-band waves well, thereby reducing the multi-station RCS of the antenna. The present invention combines the circuit analog absorber (CAA) with a multi-resonance structure and the traditional frequency selective surface (FSS) to achieve the characteristics of the radiation and scattering integrated antenna system; the FSR structure provided by the present invention is loaded above the 2×2 array antenna to achieve low RCS characteristics in a broadband range (RCS reduction bandwidth is 2GHz to 16GHz) while ensuring the normal radiation of the antenna.

[0037] Reference Figure 1The present invention provides a broadband low RCS array antenna loaded with FSR, comprising a first dielectric plate 1, a second dielectric plate 2, a third dielectric plate 3, an absorbing layer 4, a wave-transmitting layer 5, a radiation layer 6 and a metal bottom plate 7, wherein:

[0038] The wave 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 radiation layer 6 is printed on the upper surface of the third dielectric plate 3, and the metal bottom plate 7 is printed on the lower surface of the third dielectric plate 3;

[0039] The second dielectric plate 2 comprises two dielectric plates stacked together;

[0040] The wave absorbing layer 4 comprises a metal square ring 41 with four branches and a lumped resistor 42 loaded on four sides of the metal square ring 41, wherein each branch is a metal rectangular ring 43 with a bent metal strip connected to the vertex of the metal square ring, thereby forming a multi-resonance structure to combine multiple wave absorbing frequency bands and expand the wave absorbing bandwidth;

[0041] The wave-transmitting layer 5 comprises a pair of metal rings 51 and a holed 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 holed 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, realizing a wave-transmitting band to effectively radiate the electromagnetic waves of the radiation layer;

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

[0043] The specific structure of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0044] See also Figure 1 In one embodiment of the present invention, the relative dielectric constant of the first dielectric plate 1 is 3.5, the thickness is 0.6 mm, and the absorbing layer 5 is printed on the upper surface of the first dielectric plate.

[0045] The second dielectric plate 2 comprises two dielectric plates stacked one above the other, both of which have a relative dielectric constant of 2.65 and a thickness of 0.8 mm.

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

[0047] In this scheme, the two layers of 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 air cavities, wherein the air cavity height h1 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 air cavity height h2 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 The absorbing layer 4 in the present invention is arranged on the first dielectric plate 1, and a lumped resistor 42 is arranged on each side of the metal square ring 41, and the period of the absorbing layer 4 is 12 mm. In this embodiment, the inner side length L1 of the metal square ring 43 is 1.8 mm, the width W1 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, and the length L2 of the lumped resistor 42 is about 0.5 mm and the width is W1.

[0049] The outer side of each vertex of the metal square ring 41 is connected to a branch with the same structure and symmetry through a metal connecting strip 44, and the branch is a metal rectangular ring 43 with a bent metal strip 45; wherein the bent metal strip is composed of eight metal strips of uniform width, wherein the first metal strip 451 is connected to the inner middle part of a short side of the metal rectangular ring 43, the second metal strip 452 is connected to the side of the end of the first metal strip 451, the third metal strip 453 is connected to the side of the end of the second metal strip 452 and there is a gap between it and a long side of the metal rectangular ring 43; the fourth metal strip 454 is connected to the side of the end of the third metal strip 453, and the fifth metal strip 455 is connected to the end of the fourth metal strip 454. 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 band 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, 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 0.6 mm, the length L6 of the second metal strip 452 is 0.8 mm, the length L7 of the third metal strip 453 is 0.8 mm, the length L8 of the fourth metal strip 454 is 1.6 mm, the length L9 of the fifth metal strip 455 is 0.9 mm, the length L10 of the sixth metal strip 456 is 0.75 mm, the length L11 of the seventh metal strip 457 is 0.7 mm, and the length L12 of the eighth metal strip 458 is 1.6 mm.

[0052] Reference Figure 3 A bandpass FSS unit in the present invention is composed of a second dielectric plate 2 and a wave-transmitting layer 5. The wave-transmitting layer 5 is arranged on the second dielectric plate 2, and includes a pair of metal rings 51 arranged concentrically up and down and a hole-punched metal plate 52; the inner diameter d1 of the metal ring 51 is 6 mm, and the difference between the inner diameter and the outer diameter is 2.4 mm; the hole-punched metal plate 52 is placed between the two dielectric plates, and the diameter d3 of the hole to be punched out is 5.6 mm.

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

[0054] Reference Figure 5The microstrip antenna array in the radiation layer 6 of the present invention comprises four identical microstrip patch antennas 61, a feeding network 62 and a metal base plate 7; in this embodiment, the length L1 of the microstrip patch antenna 61 is 16 mm, and the width W1 is 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 feeding network 62 comprises a one-fourth equal power divider 64, wherein the first section 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 section 641 is connected to the coaxial line 65, and the two sides of the other end are respectively connected to a second section 642; the length L4 of each second section 642 is 6.3 mm, and the width W4 is 0.45 mm; each second section 6 The end of 42 is connected to a third section 643, the length L5 of the third section 643 is 6.2mm, and the width W5 is 0.85mm; each end of each third section 643 is connected to a fourth section 644, each end of the fourth section 644 is connected to the fifth section 645, the end of the fifth section 645 is connected to the sixth section 646, and the end of the sixth section 646 is inserted into the matching slot 63; wherein the fifth section 645 is perpendicular to the sixth section 646, the angle between the fourth section 644 and the fifth section 645 is an obtuse angle, and the angle between the fourth section 644 and the fifth section 645 is an acute angle; the width W6 of the fourth section 644, the fifth section 645, and the sixth section 646 are all 0.45mm, the length L6 is 8.65mm, the length L7 is 7.45mm, and the length L8 is 5.83mm. The microstrip antenna array and the power divider 64 are placed on the upper surface of the third dielectric plate 3, the metal bottom plate 7 is placed on the lower surface of the third dielectric plate 3, and the coaxial line 65 is used for feeding.

[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 commercial simulation software CST Studio Suite 2023 is used to simulate the antenna of the invention.

[0058] (2) Simulation content

[0059] Simulation 1: The return loss of the reference antenna and the invention antenna are simulated and calculated using the commercial simulation software CST Studio Suite 2023. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that the -10dB impedance bandwidth of the invented antenna is 8.6-8.85GHz, and its relative bandwidth is 2.8%. The -10dB impedance bandwidth of the reference antenna is 8.7-8.87GHz, and its relative bandwidth is 1.9%. Therefore, it can be seen that the -10dB impedance bandwidth of the invented antenna becomes wider on the basis of the reference antenna.

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

[0061] Simulation 3, using the commercial simulation software CST Studio Suite 2023 to simulate the H-plane radiation patterns of the reference antenna and the invention antenna, the results are as follows Figure 8 As shown. Figure 8 It can be seen that the gain of the antenna of the present invention is increased by about 2.4 dB compared with the reference antenna, which shows that the radiation performance of the antenna of the present invention is good.

[0062] Simulation 4: Using the commercial simulation software CST Studio Suite 2023, the single-station radar cross-section of the reference antenna and the invention antenna under the irradiation of two polarized incident waves is simulated and calculated. The results are as follows: Fig. 9 As shown. Fig. 9 It can be seen that compared with the reference antenna, the invented antenna can achieve a single-station RCS reduction outside the antenna band from 2 GHz to 16 GHz. In the x-polarization mode, the maximum single-station RCS reduction at 7.8 GHz is 43 dB; in the y-polarization mode, the maximum single-station RCS reduction at 7.8 GHz is 35 dB.

[0063] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A broadband low RCS array antenna loaded with FSR, characterized in that: It comprises a first dielectric plate (1), a second dielectric plate (2), a third dielectric plate (3), a wave absorbing layer (4), a wave transmitting layer (5), a radiation layer (6) and a metal bottom plate (7), wherein: The wave 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 radiation layer (6) is printed on the upper surface of the third dielectric plate (3), and the metal bottom plate (7) is printed on the lower surface of the third dielectric plate (3); The second dielectric plate (2) comprises two dielectric plates stacked together; The wave absorbing layer (4) comprises a metal square ring (41) with four branches and a lumped resistor (42) loaded on 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 vertex of the metal square ring (41); The wave-transmitting layer (5) comprises a pair of metal rings (51) and a holed 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); and the holed metal plate (52) is placed between the first dielectric layer and the second dielectric layer of the second dielectric plate (2); The radiation layer (6) comprises a microstrip antenna array and a feeding network (62) loaded on the upper surface of a third dielectric plate (3), and a metal base plate (7) on the lower surface of the third dielectric plate (3); the radiation layer (6) is fed by a coaxial line (65).

2. The FSR-loaded broadband low RCS array antenna according to claim 1, characterized in that: The relative dielectric constant of the first dielectric plate (1) is 3.5 and the thickness is 0.6 mm; the relative dielectric constants of the two dielectric plates in the second dielectric plate (2) are both 2.65 and the thicknesses are both 0.8 mm; the relative dielectric constant of the third dielectric plate 3 is 2.2 and the thickness is 0.6 mm.

3. The FSR-loaded broadband low RCS array antenna according to claim 1, characterized in that: The two layers of 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, wherein 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 FSR-loaded broadband low RCS array antenna according to claim 1, characterized in that: Each vertex of the metal square ring (41) is connected to a branch with the same structure and symmetry through a metal connecting strip (44), and the branch is a metal rectangular ring (43) with a bent metal strip (45); wherein the bent metal strip is composed of eight metal strips with the same width, wherein the first metal strip (451) is connected to the inner middle part of a short side of the metal rectangular ring (43), the second metal strip (452) is connected to the side of the end of the first metal strip (451), the third metal strip (453) is connected to the side of the end of the second metal strip (452) and there is a gap between it and a long side of the metal rectangular ring (43); the fourth metal strip (454) is connected to the side of the end of the third metal strip (453), and the fifth metal strip (455) is connected to the side of the end of the fourth metal strip (454). and there is a gap between the sixth metal strip (456) 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).

5. The FSR-loaded broadband low RCS array antenna according to claim 4, characterized in that: The inner side length of the metal square ring (43) is 1.8 mm, the width of each side is 0.3 mm, and four lumped resistors (42) with a resistance value of 120 Ω are respectively loaded at the center of each side of the metal square ring (41), and 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 (43) 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 FSR-loaded broadband low RCS array antenna 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 circular hole dug out on the hole-digging metal plate (52) is 5.6 mm.

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

8. The FSR-loaded broadband low RCS array antenna according to claim 1, characterized in that: The microstrip antenna array in the radiation layer (6) comprises four identical microstrip patch antennas (61), a feeding network (62) and a metal base plate (7); the feeding network (62) comprises a one-to-four equal power divider (64), wherein one end of the first section (641) is connected to a coaxial line (65), and the two sides of the other end are respectively connected to a second section (642); the end of each second section (642) is connected to a third section (643), the two sides of the end of each third section (643) are respectively connected to a fourth section (644), the end of each fourth section (644) is connected to a fifth section (645), the end of the fifth section (645) is connected to a sixth section (646), and the end of the sixth section (646) is inserted into the matching slot (63); wherein the fifth section (645) is perpendicular to the sixth section (646), the angle between the fourth section (644) and the fifth section (645) is an obtuse angle, and the angle between the fourth section (644) and the third section (643) is an acute angle.

9. The FSR-loaded broadband low RCS array antenna 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 section (641) of the power divider (64) has a length of 7.1 mm and a width of 1.5 mm, and each second section (642) has a length of 6.3 mm and a width of 0.45 mm; the third section (643) has a length of 6.2 mm and a width of 0.85 mm; the fourth section (644), the fifth section (645), and the sixth section (646) are all 0.45 mm wide, the fourth section (644) has a length of 8.65 mm, the fifth section (645) has a length of 7.45 mm, and the sixth section (646) has a length of 5.83 mm.

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