Design method of broadband low-RCS metasurface antenna with reconfigurable frequency and phase

Abstract

The method comprises the steps that according to the low RCS frequency band requirement of the antenna, a reconfigurable metasurface unit with four reflection frequency bands for incident waves is designed, and the effective phase difference between every two adjacent reflection phase curves ranges from 180 degrees + / -37 degrees; a feed technology is combined, so that part of the structure of the metasurface is effectively excited, and the metasurface antenna with reconfigurable frequency and reflection phase is quickly obtained; and forming an n * n array by the obtained metasurface antennas, and enabling the array antenna to have a low RCS characteristic in any one of three frequency bands by controlling the active regulation and control device of each metasurface antenna unit according to a code arrangement mode conforming to phase cancellation, thereby obtaining a broadband low RCS array. The reconfigurable metasurface unit and the antenna are integrally designed, the design process of the broadband low-RCS antenna is accelerated, the stealth bandwidth of the low-RCS antenna is expanded in a frequency reconfigurable mode, and the reconfigurable broadband stealth antenna is simple in structure, light in weight, low in cost and wide in application prospect.

Description

Technical Field

[0001] The present invention relates to a reconfigurable broadband low radar cross section (RCS) metasurface antenna technology, and in particular to a design method for a frequency and phase reconfigurable broadband low RCS metasurface antenna. The metasurface antenna designed by this method can form a broadband low RCS array. Background Art

[0002] The strong scattering of the antenna is an important factor that restricts the stealth performance of the stealth platform. Therefore, reducing the radar cross section (RCS) of the antenna is crucial to achieving the overall stealth of the platform. The antenna itself radiates electromagnetic waves outward. While reducing its RCS, its radiation performance must not be affected. However, traditional low RCS design methods such as coating with absorbing materials and special shape design often deteriorate the radiation performance of the antenna and are difficult to apply to the RCS reduction of the antenna. The emergence of metasurface technology provides a new path for reducing the RCS of antennas. Metasurfaces can achieve flexible control of important characteristic quantities of electromagnetic waves such as amplitude, phase, polarization and propagation direction. At the same time, they have the advantages of low profile, light weight, and easy conformality, which is very suitable for antenna stealth design. Early publicly reported low RCS antennas based on metasurfaces mostly directly load the metasurface around the existing antenna, which adds complexity to the antenna design and optimization process and easily leads to an increase in the volume of the antenna. In addition, most of the existing reports use fixed-performance metasurfaces to reduce antenna RCS, which results in the antenna's RCS reduction performance being fixed and unadjustable. This method cannot adapt to the more diverse radar detection methods and complex and changing electromagnetic environments in the future. Therefore, finding feasible ways and methods to achieve dynamic stealth of antennas is of great significance for platforms to maintain stealth capabilities in future battlefields. With the emergence of reconfigurable metasurface technology, researchers have applied it to antenna stealth design, giving antennas the potential for dynamic stealth.

[0003] Currently, there are two main problems in using reconfigurable metasurfaces for low RCS antenna design: one is how to achieve a more compact structure by integrating the reconfigurable metasurface with the antenna structure to solve the problem of increased antenna volume after loading the metasurface using traditional methods; the other is how to expand the reconfigurable frequency band to solve the problem of narrow stealth bandwidth of the reconfigurable metasurface. Summary of the invention

[0004] In order to increase the stealth bandwidth of the antenna and realize the integration of the reconfigurable metasurface and the antenna structure, the present invention proposes a frequency and phase reconfigurable metasurface antenna, hereinafter referred to as "antenna", which is a rectangular thin sheet structure; the antenna includes a top metal patch 01, a dielectric substrate 02, and a metal floor 03 from top to bottom, and the antenna unit also includes a feeding metal probe 04 that penetrates the antenna unit from top to bottom, a metal cylinder 05 that penetrates the antenna from top to bottom, and a first radio frequency switch diode 06 and a second radio frequency switch diode 07 on the top metal patch 01; wherein

[0005] The dielectric substrate 02 is a rectangular thin sheet, and its length and width are respectively the length and width of the metasurface;

[0006] The metal patch 01 is attached to the upper surface of the dielectric substrate 02, and includes a rectangular metal radiation patch 08, a left metal transmission line 09, and a right metal transmission line 10;

[0007] The projection of the center of the metal radiation patch 08 on the horizontal plane coincides with the projection of the center of the dielectric substrate 02 on the horizontal plane, and the four sides of the metal radiation patch 08 are respectively parallel to the four sides of the dielectric substrate 02; with the center of the upper surface of the metal radiation patch 08 as the coordinate origin, a rectangular coordinate system XYZ is established, the X axis is the horizontal axis pointing to the right, the Y axis is the vertical axis pointing upward, and the Z axis is the axis perpendicular to the paper and pointing outward; the horizontal and vertical symmetry axes of the rectangular metal radiation patch 08 coincide with the X axis and the Y axis respectively, and the edges of the rectangular metal radiation patch 08 in the front, back, left and right directions all keep a distance from the corresponding edges of the dielectric substrate 02;

[0008] The left metal transmission line 09 is in an "L" shape, including an integrated horizontal part and a vertical part; the horizontal symmetry axis of the horizontal part coincides with the X-axis, and the right edge of the horizontal part is spaced apart from the left edge of the rectangular metal radiation patch 08, and is connected through the first RF switch diode 06; the vertical part is located on the left side of the horizontal part, and its left and right sides are parallel to the left edge of the dielectric substrate 02, its left edge is spaced apart from the left edge of the dielectric substrate 02, and its top edge is parallel to and spaced apart from the upper edge of the dielectric substrate 02;

[0009] The right metal transmission line 10 is a small rectangular block, whose horizontal symmetry axis coincides with the X-axis. The left edge of the small rectangular block is spaced apart from the right edge of the rectangular metal radiation patch 08, and is connected via the second RF switch diode 07. The right edge of the small rectangular block is spaced apart from the right edge of the dielectric substrate 02. The right metal transmission line 10 is also electrically connected to the metal cylinder 05 that runs through the upper and lower surfaces of the antenna.

[0010] The metal floor 03 is a thin metal plate, which completely covers the lower surface of the dielectric substrate 02 and fits closely therewith;

[0011] The positive electrode of the first RF switch diode 06 is welded to the left end of the rectangular metal radiation patch 08, and the negative electrode is welded to the right end of the left metal transmission line 09; the positive electrode of the second RF switch diode 07 is welded to the right end of the rectangular metal radiation patch 08, and the negative electrode is welded to the left end of the right metal transmission line 10;

[0012] The feeding metal probe 04 of the coaxial cable passes through the antenna perpendicularly to the upper surface of the antenna and is electrically connected to the rectangular metal radiation patch 08. The center of the feeding metal probe 04 is located at the negative half axis of the Y axis and is spaced from the origin O. The feeding metal probe 04 continues to penetrate the antenna from top to bottom until it passes through the lower surface of the metal floor 03. The feeding metal probe 04 does not contact the metal floor 03 located on the lower surface of the antenna.

[0013] The metal column 05 penetrates the antenna from top to bottom perpendicularly to the upper surface of the antenna, and the center of its upper surface is located at the intersection of the X-axis and the right edge of the right metal transmission line 10. The metal cylinder 05 is in electrical contact with the right metal transmission line 10 on the upper surface of the antenna and the metal floor 03 on the lower surface.

[0014] In one embodiment of the present invention, the metal thickness of the metasurface antenna metal patch 01, the metal floor 03, the left metal transmission line 09, and the right metal transmission line 10 is in the range of 0.01-1 mm.

[0015] In another embodiment of the present invention, the side length ax of the dielectric substrate 02 along the X-axis direction is within the range of 20-40 mm, the side length ay along the Y-axis direction is within the range of 20-40 mm, and the thickness t is within the range of 1.0-5.0 mm.

[0016] In a specific embodiment of the present invention, the dielectric substrate 02 has a side length ax along the X-axis direction of 25.0 mm, a side length ay along the Y-axis direction of 25.0 mm, a thickness t of 3 mm, and a dielectric constant in the range of 2.0-4.0.

[0017] In yet another embodiment of the present invention,

[0018] The side length w of the rectangular metal radiation patch 08 along the X-axis direction is within the range of 2.0-18.0 mm, and the side length l along the Y-axis direction is within the range of 2.0-20.0 mm;

[0019] The width m of the left metal transmission line 09 is in the range of 1.0-3.5mm, the horizontal length dx1 is in the range of 0.5-8.0mm, and the vertical length dy is in the range of 0.5-10.0mm. The width of the right metal transmission line 10 is also m, and the horizontal length dx2 is in the range of 0.5-10.0mm; the distance between the left metal transmission line 09 and the left edge of the rectangular metal radiation patch 08 is in the range of 0.5-2mm; the distance between the right metal transmission line 10 and the right edge of the rectangular metal radiation patch 08 is in the range of 0.5-2mm.

[0020] In another specific embodiment of the present invention,

[0021] The side length w of the rectangular metal radiation patch 08 along the X-axis direction is 15.0 mm, and the side length l along the Y-axis direction is 17.0 mm;

[0022] The width m of the left metal transmission line 09 is 1.5mm, the horizontal length dx1 is 4mm, and the vertical length dy is 6mm. The width of the right metal transmission line 10 is 1.5mm, and the horizontal length dx2 is 1mm. The distance between the left metal transmission line 09 and the left edge of the rectangular metal radiation patch 08 is 1mm; the distance between the right metal transmission line 10 and the right edge of the rectangular metal radiation patch 08 is 1mm.

[0023] In another embodiment of the present invention, the feeding metal probe 04 is cylindrical, the maximum dimension of the cross section parallel to the XY plane is in the range of 0.2-1.5 mm, and the distance between the center of the feeding metal probe 04 and the origin O is in the range of 0.5-10 mm.

[0024] In another specific embodiment of the present invention, the feeding metal probe 04 is cylindrical, with a radius of 0.5 mm, and the distance between the center of the feeding metal probe 04 and the origin O is 4.6 mm.

[0025] In another specific embodiment of the present invention, the dielectric substrate 02 is a rectangular sheet with a square upper surface.

[0026] A method for designing a frequency and phase reconfigurable broadband low RCS metasurface antenna is also provided. The method is based on the frequency and phase reconfigurable metasurface antenna and specifically includes the following steps:

[0027] Step 1: According to the low RCS frequency band requirements of the antenna, a reconfigurable metasurface unit with four adjustable reflection frequency bands for the incident wave is designed to meet the phase difference between two adjacent phase curves within the range of 180°±37°, which is the effective phase difference; the metasurface unit should also meet the reflection amplitude of -2 to 0 dB in the frequency range of the effective phase difference, so that the reflection loss is small;

[0028] Step 2: According to the designed metasurface unit, forced feeding or coupled feeding is selected so that the metasurface unit is effectively stimulated to radiate and has a radiation pattern that meets the antenna performance requirements, thereby obtaining a metasurface antenna;

[0029] Step 3: Arrange the metasurface antennas obtained in the second step into an n×n array. By controlling the active control devices of each unit and following a coding arrangement that conforms to phase cancellation, the array antenna can have low RCS characteristics in any of the three frequency bands where the effective phase difference is located, thereby obtaining a broadband low RCS array.

[0030] The advantages of the present invention are:

[0031] 1. A new method for extending the stealth bandwidth is provided. By using only two RF diodes, the metasurface unit can have four reflection phases, and the two adjacent phase curves meet the phase cancellation condition. Therefore, the effective bandwidth can be extended in a frequency-reconfigurable manner, and the array has broadband and low RCS characteristics.

[0032] 2. By exciting the metal patch of the metasurface unit and combining it with appropriate feeding technology, the integrated design of the metasurface unit and the microstrip antenna is realized, and a frequency and phase reconfigurable metasurface antenna with a simple and compact structure is quickly obtained.

[0033] 3. Compared with the prior art, the frequency and phase reconfigurable metasurface antenna and the method for forming a broadband low RCS array proposed in the present invention can expand the stealth bandwidth of the reconfigurable low RCS antenna, accelerate the design process of the broadband low RCS antenna, and the scattering pattern is controllable. The reconfigurable broadband stealth antenna designed in this way has a simple structure, light weight, low cost, and a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0035] Figure 1 Schematic diagram of the structure of the frequency and phase reconfigurable metasurface antenna of the present invention. Figure 1 (a) is a top view, Figure 1 (b) is a front view; the corresponding relationship of the components is described by dotted lines in the figure;

[0036] Figure 2 A curve diagram showing the reflection coefficient of the antenna feeding port of the present invention changing with frequency;

[0037] Figure 3 is the reflection performance of the antenna of the present invention under vertical irradiation of an X-polarized plane wave, wherein Figure 3 (a) is a graph showing the antenna reflection phase changing with frequency in different conduction and cutoff states of the two diodes. Figure 3 (b) is a graph showing the variation of antenna reflection amplitude with frequency under different conduction and cut-off states of the two diodes;

[0038] Figure 4 The single-station RCS of the 8×8 array composed of the frequency and phase reconfigurable metasurface antennas of the present invention is arranged according to the classic chessboard coded array when the X-polarized plane wave is vertically incident and the single-station RCS curve of the 8×8 array composed of reference antennas.

[0039] Figure numerals: 01 metal patch, 02 dielectric substrate, 03 metal floor, 04 feeding metal probe, 05 metal cylinder, 06 RF diode, 07 RF diode, 08 metal radiation patch, 09 left metal transmission line, 10 right metal transmission line. DETAILED DESCRIPTION

[0040] The present invention is described below with reference to the accompanying drawings.

[0041] In order to increase the stealth bandwidth of the antenna and realize the integration of the reconfigurable metasurface and the antenna structure, the present invention proposes a design method for a broadband low RCS metasurface antenna with reconfigurable frequency and phase, which specifically includes the following steps:

[0042] Step 1: According to the low RCS frequency band requirements of the antenna, a reconfigurable metasurface unit with four adjustable reflection frequency bands for the incident wave is designed to meet the phase difference between two adjacent phase curves within the range of 180°±37°. This phase difference is defined as the effective phase difference. The metasurface unit should also meet the reflection amplitude of -2 to 0 dB in the frequency range of the effective phase difference, that is, the reflection loss is small.

[0043] Step 2: According to the designed metasurface unit, select antenna feeding technology well known in the art such as forced feeding or coupled feeding, so that the metasurface unit is effectively stimulated to radiate and has a radiation pattern that meets the antenna performance requirements, thereby obtaining a metasurface antenna.

[0044] Step 3: Arrange the metasurface antennas obtained in the second step into an n×n array. By controlling the active control devices of each unit and following a coding arrangement that conforms to phase cancellation, the array antenna can have low RCS characteristics in any of the three frequency bands where the effective phase difference is located, thereby obtaining a broadband low RCS array.

[0045] Figure 1 The present invention proposes a frequency and phase reconfigurable metasurface antenna (hereinafter referred to as "antenna"), which is a rectangular thin sheet structure. Figure 1 (a) is the top view of the antenna. Figure 1(b) is a front view of the antenna. The antenna includes a top metal patch 01, a dielectric substrate 02, and a metal floor 03 from top to bottom. The antenna unit also includes a feeding metal probe 04 that penetrates the antenna unit from top to bottom, a metal cylinder 05 that penetrates the antenna from top to bottom, and a first RF switch diode 06 and a second RF switch diode 07 on the top metal patch 01.

[0046] The dielectric substrate 02 is a rectangular thin sheet, and its length and width are respectively the length and width of the metasurface; in a specific embodiment of the present invention, the dielectric substrate 02 is a rectangular thin sheet with a square upper surface.

[0047] The metal patch 01 is attached to the upper surface of the dielectric substrate 02 , and is composed of a rectangular metal radiation patch 08 , a left metal transmission line 09 , and a right metal transmission line 10 .

[0048] The projection of the center of the metal radiation patch 08 on the horizontal plane coincides with the projection of the center of the dielectric substrate 02 on the horizontal plane, and the four sides of the metal radiation patch 08 are respectively parallel to the four sides of the dielectric substrate 02. With the center of the upper surface of the metal radiation patch 08 as the coordinate origin, a rectangular coordinate system XYZ is established. Figure 1 (a), the X axis is the horizontal axis pointing to the right, the Y axis is the vertical axis pointing upward, and the Z axis is the axis perpendicular to the paper and pointing outward. Therefore, the horizontal and vertical symmetry axes of the rectangular metal radiation patch 08 coincide with the X axis and the Y axis respectively, and the edges of the rectangular metal radiation patch 08 in the front, back, left, and right directions all maintain a certain distance from the corresponding edges of the dielectric substrate 02.

[0049] The left metal transmission line 09 is in an "L" shape, including an integrated horizontal part and a vertical part. The horizontal symmetry axis of the horizontal part coincides with the X-axis, and the right edge of the horizontal part is spaced apart from the left edge of the rectangular metal radiation patch 08 and connected through the first RF switch diode 06. The vertical part is located on the left side of the horizontal part, and its left and right sides are parallel to the left edge of the dielectric substrate 02, its left edge is kept at a certain distance from the left edge of the dielectric substrate 02, and its top edge is parallel to the upper edge of the dielectric substrate 02 and keeps a certain distance.

[0050] The right metal transmission line 10 is a small rectangular block, whose horizontal symmetry axis coincides with the X-axis, and the left edge of the rectangular block is spaced from the right edge of the rectangular metal radiation patch 08, and is connected through the second RF switch diode 07. The right edge of the rectangular block is spaced from the right edge of the dielectric substrate 02. In addition, the right metal transmission line 10 is also electrically connected to the metal cylinder 05 that runs through the upper and lower surfaces of the antenna.

[0051] The metal floor 03 is a thin metal plate, which completely covers the lower surface of the dielectric substrate 02 and is closely attached thereto. Therefore, the length and width of the metal floor 03 are the same as those of the dielectric substrate 02 .

[0052] The positive electrode of the first RF switch diode 06 is welded to the left end of the rectangular metal radiation patch 08, and the negative electrode is welded to the right end of the left metal transmission line 09. The positive electrode of the second RF switch diode 07 is welded to the right end of the rectangular metal radiation patch 08, and the negative electrode is welded to the left end of the right metal transmission line 10.

[0053] In order to feed the antenna, the feeding metal probe 04 of the coaxial cable passes through the antenna perpendicularly to the upper surface of the antenna, and the center of the feeding metal probe 04 is located at the negative half axis of the Y axis (from Figure 1 (a), the center of the feeding metal probe 04 is located in the lower half of the upper surface of the antenna), and there is a certain distance from the origin O, and it continues to penetrate the antenna from top to bottom until it passes through the lower surface of the metal floor 03, and the feeding metal probe 04 is not in contact with the metal floor 03 located on the lower surface of the antenna. Therefore, the feeding metal probe 04 is only electrically connected to the rectangular metal radiation patch 08 and is not in contact with the metal floor 03. To ensure no contact, a piece of metal is dug out on the metal floor 03 around the position where the feeding metal probe 04 passes through, so that there is no conductive connection between the feeding metal probe 04 and the metal layer of the metal floor 03, thereby maintaining insulation.

[0054] The metal column 05 penetrates the antenna from top to bottom perpendicularly to the upper surface of the antenna, and the center of its upper surface is located at the intersection of the X-axis and the right edge of the right metal transmission line 10. The metal cylinder 05 is electrically contacted with the right metal transmission line 10 located on the upper surface of the antenna and the metal floor 03 on the lower surface, thereby being able to effectively change the resonant state of the metasurface antenna of the present invention by controlling the on and off of the second RF switch diode 07 to obtain different reflection phases.

[0055] The antenna dimensions of a specific embodiment of the present invention are as follows:

[0056] The metal thickness of the metasurface antenna metal patch 01, the metal floor 03, the left metal transmission line 09, and the right metal transmission line 10 is in the range of 0.01-1 mm, with a preferred value of 0.035 mm. Conventional conductive materials such as copper, silver, and aluminum or other conductive materials can be used.

[0057] Combination Figure 1 As shown, the side length ax of the dielectric substrate 02 along the X-axis direction is in the range of 20-40 mm, preferably 25.0 mm, the side length ay along the Y-axis direction is in the range of 20-40 mm, preferably 25.0 mm, the thickness t is in the range of 1.0-5.0 mm, preferably 3 mm, and the dielectric constant is in the range of 2.0-4.0, preferably 2.65;

[0058] The side length w of the rectangular metal radiation patch 08 along the X-axis direction is in the range of 2.0-18.0 mm, preferably 15.0 mm, and the side length l along the Y-axis direction is in the range of 2.0-20.0 mm, preferably 17.0 mm;

[0059] The width m of the left metal transmission line 09 is in the range of 1.0-3.5mm, and the preferred value (the horizontal and vertical widths are the same) is 1.5mm. The horizontal length dx1 is in the range of 0.5-8.0mm, and the preferred value is 4mm. The vertical length dy is in the range of 0.5-10.0mm, and the preferred value is 6mm. The width of the right metal transmission line 10 is also m, and the preferred value is 1.5mm. The horizontal length dx2 is in the range of 0.5-10.0mm, and the preferred value is 1mm. The distance between the left metal transmission line 09 and the left edge of the rectangular metal radiation patch 08 is in the range of 0.5-2mm, and the preferred value is 1mm. The first RF switch diode 06 is used to connect them in the middle; the distance between the right metal transmission line 10 and the right edge of the rectangular metal radiation patch 08 is in the range of 0.5-2mm, and the preferred value is 1mm. The second RF switch diode 07 is used to connect them in the middle.

[0060] The feeding metal probe 04 is cylindrical, preferably cylindrical, and the maximum dimension of the cross section parallel to the XY plane (preferably the circular radius) is in the range of 0.2-1.5 mm, preferably 0.5 mm, and the distance between the center of the feeding metal probe 04 and the origin O is in the range of 0.5-10 mm, preferably 4.6 mm;

[0061] The length and width of the metal floor 03 are the same as those of the dielectric substrate 02, the side length along the X-axis direction is the same as ax, and the side length along the Y-axis direction is the same as ay, and there is a cylindrical cavity with a radius in the range of 0.6-3mm and a preferred value of 1mm, centered at the center of the feeding metal probe 04, which is used to isolate the metal probe 04.

[0062] The three-dimensional full-wave electromagnetic simulation software Ansoft HFSS19 is used to simulate the antenna of the present invention and the 8×8 array formed. For the convenience of comparison, a conventional rectangular patch microstrip antenna well known in the art is used as a reference antenna, whose dielectric, metal floor, and feed are the same as those of the antenna of the present invention, and the metal radiation patch is the same as the rectangular metal radiation patch 08 of the antenna of the present invention. Figure 2 By comparing the simulation results of the reflection coefficient variation with frequency of the reference antenna and the antenna of the present invention, it can be seen that the -10 dB working bandwidth of the reference antenna and the antenna of the present invention is almost the same. Figure 3The reflection performance of the antenna of the present invention under vertical irradiation of an X-polarized plane wave is illustrated as follows. The cut-off state of the RF diode is defined as "0" and the on state is defined as "1", then "00" indicates that both the RF switch diode 06 and the RF switch diode 07 are cut off; "01" indicates that the first RF switch diode 06 is cut off and the second RF switch diode 07 is turned on; "10" indicates that the RF switch diode 06 is turned on and the RF switch diode 07 is cut off; "11" indicates that both the RF switch diode 06 and the RF switch diode 07 are turned on. Figure 3 (a) When the two RF diodes are in different on / off states, the phase difference between the two adjacent phase curves within a certain frequency band is in the range of 180°±37°, thus three continuous frequency bands covering 4.4 GHz-6.6 GHz can be obtained; Figure 3 (b) When the two radio frequency diodes of the antenna of the present invention are in different on / off states, the reflection amplitude of the antenna is above -2 dB.

[0063] When simulating RCS, an X-polarized plane wave is irradiated vertically along the -Z direction, and an 8×8 array composed of antennas of the present invention is simulated according to a chessboard coding layout and an 8×8 array composed of reference antennas. Figure 4 The single-station RCS obtained by simulation is given for comparison. The reference antenna is a traditional rectangular patch microstrip antenna well known in the art, and its dielectric, metal floor, and feed are the same as those of the antenna of the present invention. The metal radiation patch is the same as the rectangular metal radiation patch 08 of the antenna of the present invention. Figure 4 Code 1 indicates that the chessboard codes of the array are "00" and "10"; Code 2 indicates that the chessboard codes of the array are "00" and "01"; Code 3 indicates that the chessboard codes of the array are "01" and "11". It can be seen that by controlling the conduction or cutoff of the first RF switch diode 06 and the second RF switch diode 07, the array composed of the antennas of the present invention can be in the coding 1 state, with low RCS at 4.0-4.8GHz, or in the coding 2 state, with low RCS at 4.8-5.7GHz, or in the coding 3 state, with low RCS at 5.7-7.0GHz. In summary, the array composed of the antennas of the present invention has a significant RCS reduction effect at 4.0GHz-7.0GHz compared to the array composed of the reference antennas, and the RCS reduction at 4.4GHz-6.6GHz is greater than 10dB. These results show that the antenna of the present invention uses a simple, compact integrated structure to achieve the function of reconfigurable frequency and reflection phase. When it is formed into an array, it has a broadband low RCS effect by controlling the state of the RF diode compared to the array composed of traditional antennas.

[0064] The method of the present invention can expand the stealth bandwidth of the reconfigurable metasurface in a frequency-reconfigurable manner, abandoning the traditional technical route of loading the metasurface on the antenna to achieve low RCS, so as to stimulate the reconfigurable metasurface unit to obtain the metasurface antenna, and form an array with broadband low RCS characteristics.

Claims

1. A frequency and phase reconfigurable metasurface antenna, hereinafter referred to as "antenna", which is a rectangular thin sheet structure; characterized in that: The antenna comprises, from top to bottom, a top metal patch (01), a dielectric substrate (02), and a metal floor (03); the antenna unit also comprises a feeding metal probe (04) penetrating the antenna unit from top to bottom, a metal column (05) penetrating the antenna from top to bottom, and a first radio frequency switch diode (06) and a second radio frequency switch diode (07) on the top metal patch (01); wherein The dielectric substrate (02) is a rectangular thin sheet, and its length and width are respectively the length and width of the metasurface; The metal patch (01) is attached to the upper surface of the dielectric substrate (02), and comprises a rectangular metal radiation patch (08), a left metal transmission line (09), and a right metal transmission line (10); The projection of the center of the metal radiation patch (08) on the horizontal plane coincides with the projection of the center of the dielectric substrate (02) on the horizontal plane, and the four sides of the metal radiation patch (08) are respectively parallel to the four sides of the dielectric substrate (02); a rectangular coordinate system XYZ is established with the center of the upper surface of the metal radiation patch (08) as the coordinate origin, wherein the X axis is a horizontal axis pointing to the right, the Y axis is a vertical axis pointing upward, and the Z axis is an axis perpendicular to the paper and pointing outward; the horizontal and vertical symmetry axes of the rectangular metal radiation patch (08) coincide with the X axis and the Y axis respectively, and the edges of the rectangular metal radiation patch (08) in the front, back, left and right directions all keep a distance from the corresponding edges of the dielectric substrate (02); The left metal transmission line (09) is in an "L" shape, and includes an integrated horizontal portion and a vertical portion; the horizontal symmetry axis of the horizontal portion coincides with the X-axis, the right edge of the horizontal portion maintains a distance from the left edge of the rectangular metal radiation patch (08), and is connected via a first radio frequency switch diode (06); the vertical portion is located on the left side of the horizontal portion, its left and right sides are parallel to the left edge of the dielectric substrate (02), its left edge maintains a distance from the left edge of the dielectric substrate (02), and its top edge is parallel to and maintains a distance from the upper edge of the dielectric substrate (02); The right metal transmission line (10) is a small rectangular block, whose horizontal symmetry axis coincides with the X-axis; a distance is maintained between the left edge of the small rectangular block and the right edge of the rectangular metal radiation patch (08), and they are connected via a second radio frequency switch diode (07); a distance is maintained between the right edge of the small rectangular block and the right edge of the dielectric substrate (02); the right metal transmission line (10) is also electrically connected to a metal column (05) that runs through the upper and lower surfaces of the antenna; The metal floor (03) is a thin metal plate, which completely covers the lower surface of the dielectric substrate (02) and fits closely thereto; The positive electrode of the first radio frequency switch diode (06) is welded to the left end of the rectangular metal radiation patch (08), and the negative electrode is welded to the right end of the left metal transmission line (09); the positive electrode of the second radio frequency switch diode (07) is welded to the right end of the rectangular metal radiation patch (08), and the negative electrode is welded to the left end of the right metal transmission line (10); The feeding metal probe (04) of the coaxial cable passes through the antenna perpendicularly to the upper surface of the antenna and is electrically connected to the rectangular metal radiation patch (08). The center of the feeding metal probe (04) is located on the negative half axis of the Y axis and is spaced from the origin O. The feeding metal probe (04) continues to penetrate the antenna from top to bottom until it passes through the lower surface of the metal floor (03). The feeding metal probe (04) does not contact the metal floor (03) located on the lower surface of the antenna. The metal column (05) penetrates the antenna from top to bottom perpendicularly to the upper surface of the antenna, and the center of its upper surface is located at the intersection of the X-axis and the right edge of the right metal transmission line (10). The metal column (05) is in electrical contact with the right metal transmission line (10) located on the upper surface of the antenna and the metal floor (03) on the lower surface.

2. The frequency and phase reconfigurable metasurface antenna according to claim 1, characterized in that: The metal thickness of the metasurface antenna metal patch (01), the metal floor (03), the left metal transmission line (09), and the right metal transmission line (10) is in the range of 0.01-1 mm.

3. The frequency and phase reconfigurable metasurface antenna according to claim 1, characterized in that: The dielectric substrate (02) has a side length ax in the X-axis direction in the range of 20-40 mm, a side length ay in the Y-axis direction in the range of 20-40 mm, and a thickness t in the range of 1.0-5.0 mm.

4. The frequency and phase reconfigurable metasurface antenna according to claim 3, characterized in that: The dielectric substrate (02) has a side length ax along the X-axis direction of 25.0 mm, a side length ay along the Y-axis direction of 25.0 mm, a thickness t of 3 mm, and a dielectric constant within the range of 2.0-4.

0.

5. The frequency and phase reconfigurable metasurface antenna according to claim 1, characterized in that: The side length w of the rectangular metal radiation patch (08) along the X-axis direction is within the range of 2.0-18.0 mm, and the side length l along the Y-axis direction is within the range of 2.0-20.0 mm; The width m of the left metal transmission line (09) is in the range of 1.0-3.5 mm, the horizontal length dx1 is in the range of 0.5-8.0 mm, and the vertical length dy is in the range of 0.5-10.0 mm. The width of the right metal transmission line (10) is also m, and the horizontal length dx2 is in the range of 0.5-10.0 mm. The distance between the left metal transmission line (09) and the left edge of the rectangular metal radiation patch (08) is in the range of 0.5-2 mm; the distance between the right metal transmission line (10) and the right edge of the rectangular metal radiation patch (08) is in the range of 0.5-2 mm.

6. The frequency and phase reconfigurable metasurface antenna according to claim 5, characterized in that: The side length w of the rectangular metal radiation patch (08) along the X-axis direction is 15.0 mm, and the side length l along the Y-axis direction is 17.0 mm; The left metal transmission line (09) has a width m of 1.5 mm, a horizontal length dx1 of 4 mm, and a vertical length dy of 6 mm; the right metal transmission line (10) has a width of 1.5 mm, and a horizontal length dx2 of 1 mm; the distance between the left metal transmission line (09) and the left edge of the rectangular metal radiation patch (08) is 1 mm; the distance between the right metal transmission line (10) and the right edge of the rectangular metal radiation patch (08) is 1 mm.

7. The frequency and phase reconfigurable metasurface antenna according to claim 1, characterized in that: The feeding metal probe (04) is cylindrical, and the maximum dimension of its cross section parallel to the XY plane is within the range of 0.2-1.5 mm. The distance between the center of the feeding metal probe (04) and the origin O is within the range of 0.5-10 mm.

8. The frequency and phase reconfigurable metasurface antenna according to claim 7, characterized in that: The feeding metal probe (04) is cylindrical, with a radius of 0.5 mm, and the distance between the center of the feeding metal probe 04 and the origin O is 4.6 mm.

9. The frequency and phase reconfigurable metasurface antenna according to claim 1, characterized in that: The dielectric substrate (02) is a rectangular thin sheet with a square upper surface.

10. A method for designing a frequency and phase reconfigurable broadband low RCS metasurface antenna, based on the frequency and phase reconfigurable metasurface antenna according to any one of claims 1 to 9, characterized in that: The specific steps include: Step 1: According to the low RCS frequency band requirements of the antenna, a reconfigurable metasurface unit with four adjustable reflection frequency bands for the incident wave is designed to meet the phase difference between two adjacent phase curves within the range of 180°±37°, which is the effective phase difference; the metasurface unit should also meet the reflection amplitude of -2 to 0 dB in the frequency range of the effective phase difference, so that the reflection loss is small; Step 2: According to the designed metasurface unit, forced feeding or coupled feeding is selected so that the metasurface unit is effectively stimulated to radiate and has a radiation pattern that meets the antenna performance requirements, thereby obtaining a metasurface antenna; Step 3: Arrange the metasurface antennas obtained in the second step into an n×n array. By controlling the active control devices of each unit and following a coding arrangement that conforms to phase cancellation, the array antenna can have low RCS characteristics in any of the three frequency bands where the effective phase difference is located, thereby obtaining a broadband low RCS array.

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