A frequency and phase reconfigurable broadband low rcs metasurface antenna design method

Abstract

This paper proposes a design method for a frequency- and phase-reconfigurable broadband low-RCS metasurface antenna. Based on the low-RCS frequency band requirement of the antenna, a reconfigurable metasurface element with four reflection frequency bands for the incident wave is designed, with adjacent reflection phase curves having an effective phase difference of 180°±37°. Combined with feeding technology, a portion of the metasurface structure is effectively excited, quickly obtaining a frequency- and reflection phase-reconfigurable metasurface antenna. The resulting metasurface antenna is constructed into an n×n array. By controlling the active modulation devices of each metasurface antenna element and arranging them according to a phase-cancellation coding scheme, the array antenna can exhibit low RCS characteristics in any of the three frequency bands, resulting in a broadband low-RCS array. This invention integrates the reconfigurable metasurface element and the antenna design, accelerating the design process of broadband low-RCS antennas. It also extends the stealth bandwidth of low-RCS antennas through frequency reconfiguration. The reconfigurable broadband stealth antenna has a simple structure, light weight, low cost, and broad application prospects.

Description

Technical Field

[0001] This invention relates to reconfigurable broadband low radar cross section (RCS) metasurface antenna technology, specifically to a design method for a frequency and phase reconfigurable broadband low RCS metasurface antenna, which can be used to design a broadband low RCS array. Background Technology

[0002] The strong scattering property of an antenna is a significant factor limiting the stealth performance of a stealth platform. Therefore, reducing the antenna's radar cross section (RCS) is crucial for achieving overall platform stealth. Since antennas radiate electromagnetic waves, reducing their RCS must be done while preserving their radiation performance. However, traditional low-RCS design methods, such as coating with absorbing materials and special shape designs, often degrade the antenna's radiation performance, making them unsuitable for RCS reduction. The emergence of metasurface technology provides a new path for reducing antenna RCS. Metasurfaces allow for flexible control of important electromagnetic wave characteristics such as amplitude, phase, polarization, and propagation direction, while also offering advantages such as low profile, light weight, and conformal design, making them highly suitable for antenna stealth design. Early publicly reported low-RCS antennas based on metasurfaces mostly involved directly adding the metasurface around existing antennas, which increased the complexity of the antenna design and optimization process and could lead to an increase in antenna size. Furthermore, existing reports mostly utilize metasurfaces with fixed performance to reduce antenna RCS, resulting in fixed and unadjustable RCS reduction performance. This method cannot adapt to the more diverse radar detection methods and complex and variable electromagnetic environments of the future. Therefore, finding feasible ways and methods to achieve dynamic antenna stealth is of great significance for platforms to maintain stealth capabilities on the future battlefield. With the emergence of reconfigurable metasurface technology, researchers have applied it to antenna stealth design, enabling antennas to possess the potential for dynamic stealth.

[0003] Currently, the use of reconfigurable metasurfaces in low RCS antenna design faces two main challenges: first, 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; and second, how to expand the reconfigurable frequency band to solve the problem of narrow stealth bandwidth of reconfigurable metasurfaces. Summary of the Invention

[0004] To increase the stealth bandwidth of the antenna and achieve the integration of the reconfigurable metasurface with the antenna structure, this invention proposes a frequency and phase reconfigurable metasurface antenna, hereinafter referred to as the "antenna," which has a rectangular thin-film structure. The antenna, from top to bottom, includes a top metal patch 01, a dielectric substrate 02, and a metal ground plane 03. The antenna element also includes a feed metal probe 04 penetrating the antenna element from top to bottom, a metal cylinder 05 penetrating the antenna from top to bottom, and a first RF switching diode 06 and a second RF switching diode 07 on the top metal patch 01.

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

[0006] Metal patch 01 is attached to the upper surface of dielectric substrate 02, including rectangular metal radiating patch 08, left metal transmission line 09, and right metal transmission line 10;

[0007] The projection of the center of the metal radiating patch 08 onto the horizontal plane coincides with the projection of the center of the dielectric substrate 02 onto the horizontal plane. The four sides of the metal radiating patch 08 are 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 radiating patch 08 as the origin. 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 axes of symmetry of the rectangular metal radiating patch 08 coincide with the X-axis and Y-axis, respectively. The edges of the rectangular metal radiating patch 08 in the front, back, left, and right directions maintain a distance from the corresponding edges of the dielectric substrate 02.

[0008] The left metal transmission line 09 is L-shaped and includes an integrated horizontal and vertical section. The horizontal axis of symmetry of the horizontal section coincides with the X-axis. The right edge of the horizontal section maintains a distance from the left edge of the rectangular metal radiating patch 08 and is connected through the first RF switching diode 06. The vertical section is located to the left of the horizontal section. 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 top edge of the dielectric substrate 02.

[0009] The right metal transmission line 10 is a small rectangular block whose horizontal axis of symmetry coincides with the X-axis. The left edge of the rectangular block is spaced from the right edge of the rectangular metal radiating 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. 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 that completely covers the lower surface of the dielectric substrate 02 and is tightly bonded to it;

[0011] The positive terminal of the first RF switching diode 06 is soldered to the left end of the rectangular metal radiating patch 08, and the negative terminal is soldered to the right end of the left metal transmission line 09; the positive terminal of the second RF switching diode 07 is soldered to the right end of the rectangular metal radiating patch 08, and the negative terminal is soldered to the left end of the right metal transmission line 10.

[0012] The coaxial cable feed metal probe 04 passes through the antenna perpendicularly to the upper surface of the antenna and is electrically connected to the rectangular metal radiating patch 08. The center of the feed metal probe 04 is located on the negative half-axis of the Y-axis and maintains a distance from the origin O. It continues to penetrate the antenna from top to bottom until it exits from the lower surface of the metal ground plate 03. The feed metal probe 04 does not contact the metal ground plate 03 located on the lower surface of the antenna.

[0013] The metal cylinder 05 penetrates the antenna from top to bottom perpendicular to the upper surface of the antenna. 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 ground plane 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 ground plane 03, the left metal transmission line 09, and the right metal transmission line 10 is in the range of 0.01-1mm.

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

[0018] The rectangular metal radiating patch 08 has a side length w along the X-axis in the range of 2.0-18.0 mm and a side length l along the Y-axis in 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 radiating 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 radiating patch 08 is in the range of 0.5-2mm.

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

[0021] The rectangular metal radiating patch 08 has a side length w of 15.0 mm along the X-axis and a side length l of 17.0 mm along the Y-axis.

[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 radiating patch 08 is 1mm. The distance between the right metal transmission line 10 and the right edge of the rectangular metal radiating patch 08 is 1mm.

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

[0024] In another specific embodiment of the present invention, the power-feeding metal probe 04 is cylindrical with a radius of 0.5 mm, and the distance between the center of the power-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 thin sheet with a square upper surface.

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

[0027] Step 1: Based on the low RCS band requirements of the antenna, design a reconfigurable metasurface element with 4 adjustable reflection bands for the incident wave, ensuring that the phase difference between two adjacent phase curves is within the range of 180°±37°, which is the effective phase difference; the metasurface element should also ensure that the reflection amplitude is within -2 to 0dB in the frequency range of the effective phase difference, so as to minimize reflection loss.

[0028] Step 2: Based on the designed metasurface element, select forced feeding or coupled feeding to effectively excite and radiate the metasurface element, so that it has a radiation pattern that meets the antenna performance requirements, and obtain the metasurface antenna.

[0029] Step 3: Assemble the metasurface antennas obtained in Step 2 into an n×n array. By controlling the active modulation devices of each unit and arranging them according to the coding method 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, thus obtaining a broadband low RCS array.

[0030] The advantages of this invention are:

[0031] 1. A novel method for extending stealth bandwidth is provided, which uses only two RF diodes to achieve four reflection phases in the metasurface unit, and the adjacent two phase curves meet the phase cancellation condition. Thus, the effective bandwidth can be extended through frequency reconfiguration, and the array formed has wide bandwidth and low RCS characteristics.

[0032] 2. By exciting the metal patch of the metasurface unit and combining it with appropriate feeding technology, the metasurface unit and microstrip antenna can be integrated into a single design, quickly obtaining a metasurface antenna with reconfigurable frequency and phase, which has a simple and compact structure.

[0033] 3. Compared with existing technologies, the frequency and phase reconfigurable metasurface antenna and its method for constructing a broadband low-RCS array proposed in this invention can extend the stealth bandwidth of the reconfigurable low-RCS antenna, accelerate the design process of broadband low-RCS antennas, and provide controllable scattering patterns. The reconfigurable broadband stealth antenna designed in this way has a simple structure, is lightweight, and low-cost, with very broad application prospects. Attached Figure Description

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

[0035] Figure 1 This is a schematic diagram of the frequency and phase reconfigurable metasurface antenna structure of the present invention. Figure 1 (a) is a top view. Figure 1 (b) is a front view; the correspondence of the components is depicted by dashed lines in the figure;

[0036] Figure 2 This is a graph showing the reflection coefficient of the antenna feed port of the present invention as a function of frequency.

[0037] Figure 3 The antenna of this invention exhibits reflection performance under perpendicular illumination by an X-polarized plane wave, wherein... Figure 3 (a) is a graph showing the change of antenna reflection phase with frequency under different conduction and cutoff states of the two diodes. Figure 3 (b) is a graph showing the change of antenna reflection amplitude with frequency under different conduction and cutoff states of the two diodes;

[0038] Figure 4 The diagram shows the monostatic RCS of an 8×8 array composed of frequency and phase reconfigurable metasurface antennas of this invention, arranged according to a classic checkerboard coded array, when an X-polarized plane wave is incident perpendicularly, and the monostatic RCS curve of the 8×8 array composed of a reference antenna.

[0039] Figure reference numerals: 01 Metal patch, 02 Dielectric substrate, 03 Metal ground plane, 04 Feed metal probe, 05 Metal cylinder, 06 RF diode, 07 RF diode, 08 Metal radiating patch, 09 Left metal transmission line, 10 Right metal transmission line. Detailed Implementation

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

[0041] To increase antenna stealth bandwidth and achieve integration of reconfigurable metasurfaces with antenna structures, this invention proposes a design method for a broadband low RCS metasurface antenna with reconfigurable frequency and phase, specifically including the following steps:

[0042] Step 1: Based on the low RCS band requirements of the antenna, design a reconfigurable metasurface element with 4 adjustable reflection bands for the incident wave, satisfying that the phase difference between two adjacent phase curves is within the range of 180°±37°, and define this phase difference as the effective phase difference; the metasurface element should also satisfy that the reflection amplitude in the frequency range of the effective phase difference is within -2 to 0dB, that is, the reflection loss is small.

[0043] Step 2: Based on the designed metasurface element, select antenna feeding techniques well-known in the field, such as forced feeding or coupled feeding, so that the metasurface element is effectively excited and radiated, and has a radiation pattern that meets the antenna performance requirements, thereby obtaining the metasurface antenna.

[0044] Step 3: Assemble the metasurface antennas obtained in Step 2 into an n×n array. By controlling the active modulation devices of each unit and arranging them according to the coding method 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, thus obtaining a broadband low RCS array.

[0045] Figure 1 This invention proposes a frequency and phase reconfigurable metasurface antenna (hereinafter referred to as "antenna"), which has a rectangular thin-film structure. Figure 1 (a) is a top view of the antenna. Figure 1(b) is a front view of the antenna. The antenna includes, from top to bottom, a top metal patch 01, a dielectric substrate 02, and a metal ground plane 03. The antenna unit also includes a feed 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 switching diode 06 and a second RF switching diode 07 on the top metal patch 01.

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

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

[0048] The projection of the center of the metal radiating patch 08 onto the horizontal plane coincides with the projection of the center of the dielectric substrate 02 onto the horizontal plane. The four sides of the metal radiating patch 08 are 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 radiating patch 08 as the origin. Figure 1 (a) As you can see, the X-axis is a horizontal axis pointing to the right, the Y-axis is a vertical axis pointing upwards, and the Z-axis is an axis perpendicular to the paper and pointing outwards. Therefore, the horizontal and vertical axes of symmetry of the rectangular metal radiating patch 08 coincide with the X-axis and the Y-axis, respectively. The edges of the rectangular metal radiating 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 L-shaped, comprising an integrated horizontal and vertical section. The horizontal axis of symmetry of the horizontal section coincides with the X-axis. The right edge of the horizontal section maintains a distance from the left edge of the rectangular metal radiating patch 08 and is connected via the first RF switching diode 06. The vertical section is located to the left of the horizontal section. Both its left and right sides are parallel to the left edge of the dielectric substrate 02. Its left edge maintains a certain distance from the left edge of the dielectric substrate 02, and its top edge is parallel to and maintains a certain distance from the top edge of the dielectric substrate 02.

[0050] The right metal transmission line 10 is a small rectangular block whose horizontal axis of symmetry coincides with the X-axis. The left edge of the rectangular block maintains a distance from the right edge of the rectangular metal radiating patch 08, and they are connected via a second RF switching diode 07. The right edge of the rectangular block maintains a distance from the right edge of the dielectric substrate 02. Furthermore, the right metal transmission line 10 is electrically connected to a metal cylinder 05 that penetrates the upper and lower surfaces of the antenna.

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

[0052] The anode of the first RF switching diode 06 is soldered to the left end of the rectangular metal radiating patch 08, and the cathode is soldered to the right end of the left metal transmission line 09. The anode of the second RF switching diode 07 is soldered to the right end of the rectangular metal radiating patch 08, and the cathode is soldered to the left end of the right metal transmission line 10.

[0053] To feed the antenna, a coaxial cable feed metal probe 04 passes through the antenna perpendicularly to the upper surface of the antenna, with the center of the feed metal probe 04 located on the negative half-axis of the Y-axis (from...). Figure 1 (a) As you can see, the center of the feed metal probe 04 is located in the lower half of the upper surface of the antenna, and is a certain distance from the origin O. It continues to penetrate the antenna from top to bottom until it emerges from the lower surface of the metal ground plane 03. The feed metal probe 04 does not contact the metal ground plane 03 located on the lower surface of the antenna. Therefore, the feed metal probe 04 is only electrically connected to the rectangular metal radiating patch 08 and does not contact the metal ground plane 03. To ensure no contact, a piece of metal is removed from the metal ground plane 03 around the position where the feed metal probe 04 passes through, so that there is no conductive connection between the metal layer of the feed metal probe 04 and the metal ground plane 03, thus maintaining insulation.

[0054] The metal cylinder 05 penetrates the antenna from top to bottom perpendicular to the upper surface of the antenna. 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 ground plane 03 on the lower surface. Thus, by controlling the on and off of the second RF switch diode 07, the resonant state of the metasurface antenna of the present invention can be effectively changed to obtain different reflection phases.

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

[0056] The metal thickness of the metasurface antenna metal patch 01, metal ground plane 03, left metal transmission line 09, and right metal transmission line 10 ranges from 0.01 to 1 mm, with a preferred value of 0.035 mm. They can be made of conventional conductive materials such as copper, silver, and aluminum, or other conductive materials.

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

[0058] The rectangular metal radiating patch 08 has a side length w along the X-axis in the range of 2.0-18.0 mm, with a preferred value of 15.0 mm, and a side length l along the Y-axis in the range of 2.0-20.0 mm, with a preferred value of 17.0 mm.

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

[0060] The power-feeding metal probe 04 is cylindrical, preferably circular, and its maximum cross-sectional dimension (preferably the radius of a circle) parallel to the XY plane is in the range of 0.2-1.5mm, with a preferred value of 0.5mm. The distance between the center of the power-feeding metal probe 04 and the origin O is in the range of 0.5-10mm, with a preferred value of 4.6mm.

[0061] The length and width of the metal ground plate 03 are the same as those of the dielectric substrate 02. The side length along the X-axis is the same as ax, and the side length along the Y-axis is the same as ay. There is a cylindrical cavity with a radius of 0.6-3mm, preferably 1mm, centered on the center of the feeding metal probe 04, which is used to isolate it from the metal probe 04.

[0062] The antenna and the 8×8 array of this invention were simulated using the three-dimensional full-wave electromagnetic simulation software Ansoft HFSS19. For ease of comparison, a conventional rectangular patch microstrip antenna well-known in the art was used as a reference antenna, with the same dielectric, metal ground plane, and feed as the antenna of this invention, and the same rectangular metal radiating patch 08 as the antenna of this invention. Figure 2 By comparing the simulation results of the reflection coefficient of the reference antenna and the antenna of the present invention with frequency, it can be seen that the -10dB operating bandwidth of the reference antenna and the antenna of the present invention is almost the same. Figure 3To illustrate the reflection performance of the antenna of this invention under vertical illumination by an X-polarized plane wave, the following diagram is provided: the cutoff state of the RF diode is defined as "0" and the on state as "1". Then, "00" indicates that both RF switch diodes 06 and 07 are cut off; "01" indicates that the first RF switch diode 06 is cut off and the second RF switch diode 07 is on; "10" indicates that RF switch diode 06 is on and RF switch diode 07 is cut off; and "11" indicates that both RF switch diodes 06 and 07 are on. Figure 3 (a) When two RF diodes are in different on / off states, the phase difference between two adjacent phase curves in a certain frequency band is within the range of 180°±37°, thus three consecutive frequency bands covering 4.4GHz-6.6GHz can be obtained. Figure 3 (b) When the antenna of the present invention is in different on / off states of the two RF diodes, the reflection amplitude of the antenna is above -2dB.

[0063] During the RCS simulation, an X-polarized plane wave was perpendicularly irradiated along the -Z direction. The 8×8 array composed of the antennas of this invention was simulated according to the checkerboard coding layout and the 8×8 array composed of the reference antenna. Figure 4 The simulation results of the single-station RCS are given. The reference antenna is a conventional rectangular patch microstrip antenna well known in the art. Its dielectric, metal ground plane, and feed are the same as those of the antenna of the present invention, and the metal radiating patch is the same as the rectangular metal radiating patch 08 of the antenna of the present invention. Figure 4 In the diagram, code 1 indicates that the array's chessboard encoding uses two codes: "00" and "10"; code 2 indicates that the array's chessboard encoding uses two codes: "00" and "01"; and code 3 indicates that the array's chessboard encoding uses two codes: "01" and "11". It can be seen that by controlling the on / off state of the first RF switch diode 06 and the second RF switch diode 07, the array composed of the antennas of this invention can be in code 1 state, exhibiting a low RCS in the 4.0-4.8 GHz range; in code 2 state, exhibiting a low RCS in the 4.8-5.7 GHz range; or in code 3 state, exhibiting a low RCS in the 5.7-7.0 GHz range. In summary, the array composed of the antennas of this invention shows a significant RCS reduction effect compared to the array composed of the reference antennas in the 4.0 GHz-7.0 GHz range, with an RCS reduction of more than 10 dB in the 4.4 GHz-6.6 GHz range. These results demonstrate that the antenna of this invention achieves frequency and reflection phase reconfigurability using a simple and compact integrated structure. When configured into an array, by controlling the state of the RF diodes, it exhibits a wideband low RCS effect compared to arrays constructed from traditional antennas.

[0064] The method of this invention can extend the stealth bandwidth of reconfigurable metasurfaces through frequency reconfiguration, abandoning the traditional technical route of loading metasurfaces on antennas to achieve low RCS. Instead, it excites reconfigurable metasurface units to obtain metasurface antennas, which are then arrayed to have broadband low RCS characteristics.

Claims

1. A frequency- and phase-reconfigurable metasurface antenna, hereinafter referred to as "antenna", having a rectangular thin-film structure; characterized in that, The antenna, from top to bottom, includes a top metal patch (01), a dielectric substrate (02), and a metal ground plane (03). The antenna unit also includes a feed metal probe (04) penetrating the antenna unit from top to bottom, a metal pillar (05) penetrating the antenna from top to bottom, and a first RF switching diode (06) and a second RF switching diode (07) on the top metal patch (01). The dielectric substrate (02) is a rectangular thin sheet, the length and width of which are the length and width of the metasurface, respectively; A metal patch (01) is attached to the upper surface of a dielectric substrate (02), including a rectangular metal radiating patch (08), a left metal transmission line (09), and a right metal transmission line (10); The projection of the center of the metal radiating patch (08) onto the horizontal plane coincides with the projection of the center of the dielectric substrate (02) onto the horizontal plane. The four sides of the metal radiating patch (08) are 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 radiating patch (08) as the origin. 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 pointing outward perpendicular to the paper. The horizontal and vertical axes of symmetry of the rectangular metal radiating patch (08) coincide with the X-axis and Y-axis, respectively. The edges of the rectangular metal radiating patch (08) in the front, back, left, and right directions are all kept at a distance from the corresponding edges of the dielectric substrate (02). The left metal transmission line (09) is L-shaped and includes an integrated horizontal part and a vertical part; the horizontal axis of symmetry of the horizontal part coincides with the X-axis, the right edge of the horizontal part is spaced from the left edge of the rectangular metal radiating patch (08), and is connected through the first radio frequency switching diode (06); the vertical part is located to the left of the horizontal part, both its left and right sides are parallel to the left edge of the dielectric substrate (02), its left edge is spaced from the left edge of the dielectric substrate (02), and its top edge is parallel to and spaced from the top edge of the dielectric substrate (02); The right metal transmission line (10) is a rectangular block whose horizontal axis of symmetry coincides with the X-axis. The left edge of the rectangular block is spaced from the right edge of the rectangular metal radiating patch (08) and connected through the second RF switching diode (07). The right edge of the rectangular block is spaced from the right edge of the dielectric substrate (02). The right metal transmission line (10) is also electrically connected to the metal pillar (05) that runs through the upper and lower surfaces of the antenna. The metal floor (03) is a thin metal plate that completely covers the lower surface of the dielectric substrate (02) and is tightly bonded to it; The positive terminal of the first RF switching diode (06) is soldered to the left end of the rectangular metal radiating patch (08), and the negative terminal is soldered to the right end of the left metal transmission line (09); the positive terminal of the second RF switching diode (07) is soldered to the right end of the rectangular metal radiating patch (08), and the negative terminal is soldered to the left end of the right metal transmission line (10). The coaxial cable feed metal probe (04) passes through the antenna perpendicularly to the upper surface of the antenna and is electrically connected to the rectangular metal radiating patch (08). The center of the feed metal probe (04) is located on the negative half-axis of the Y-axis and maintains a distance from the origin O. It continues to penetrate the antenna from top to bottom until it exits from the lower surface of the metal ground plate (03). The feed metal probe (04) does not contact the metal ground plate (03) located on the lower surface of the antenna. The metal cylinder (05) penetrates the antenna from top to bottom perpendicular to the upper surface of the antenna. 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 ground plane (03) on the lower surface.

2. The frequency- and phase-reconfigurable metasurface antenna of claim 1, wherein, The metal thickness of the metasurface antenna metal patch (01), metal ground plane (03), left metal transmission line (09), and right metal transmission line (10) ranges from 0.01 to 1 mm.

3. The frequency and phase reconfigurable metasurface antenna of claim 1, wherein, The dielectric substrate (02) has a side length ax along the X-axis in the range of 20-40 mm, a side length ay along the Y-axis 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 of claim 3, wherein, The dielectric substrate (02) has a side length ax of 25.0 mm along the X-axis, a side length ay of 25.0 mm along the Y-axis, a thickness t of 3 mm, and a dielectric constant in the range of 2.0-4.

0.

5. The frequency and phase reconfigurable metasurface antenna as described in claim 1, characterized in that, The rectangular metal radiating patch (08) has a side length w along the X-axis in the range of 2.0-18.0 mm and a side length l along the Y-axis in the range of 2.0-20.0 mm. The width m of the left metal transmission line (09) is in the range of 1.0-3.5mm, 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 radiating 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 radiating patch (08) is in the range of 0.5-2mm.

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

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

8. The frequency and phase reconfigurable metasurface antenna of claim 7, wherein, The power-feeding metal probe (04) is cylindrical with a radius of 0.5 mm. The center of the power-feeding metal probe (04) is 4.6 mm away from the origin O.

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

10. A design method for a frequency- and phase-reconfigurable broadband low-RCS metasurface antenna, based on the frequency- and phase-reconfigurable metasurface antenna as described in any one of claims 1 to 9, characterized in that, Specifically, the following steps are included: Step 1: Based on the low RCS band requirements of the antenna, design a reconfigurable metasurface element with 4 adjustable reflection bands for the incident wave, ensuring that the phase difference between two adjacent phase curves is within the range of 180°±37°, which is the effective phase difference; the metasurface element should also ensure that the reflection amplitude is within -2 to 0dB in the frequency range of the effective phase difference, so as to minimize reflection loss. Step 2: Based on the designed metasurface element, select forced feeding or coupled feeding to effectively excite and radiate the metasurface element, so that it has a radiation pattern that meets the antenna performance requirements, and obtain the metasurface antenna. Step 3: Assemble the metasurface antennas obtained in Step 2 into an n×n array. By controlling the active modulation devices of each unit and arranging them according to the coding method 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, thus obtaining a broadband low RCS array.

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