A phase gradient-based coded metasurface antenna array structure and design method

Abstract

The present invention discloses a phase gradient-based coded metasurface antenna array structure, comprising a metal patch layer, a first intermediate dielectric layer, a metal floor layer, a second intermediate dielectric layer, a feed network layer, a third intermediate dielectric layer and a DC bias network layer pressed together in sequence; the metal patch layer comprises a plurality of rectangular patch units, and the lower surfaces of the patch units are connected to the feed network layer in a vertical direction through a first feed column; a second feed column is arranged on each side of the first feed column, connecting the patch unit and the DC bias network layer; the present invention also provides a corresponding design method, so that the cross-polarized scattering phase of the designed coded metasurface antenna array structure when four diodes are on and off satisfies the phase difference of 180°±37°, which can achieve the purpose of antenna band stealth inside and outside and present different dynamic scattering effects.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave antenna design, and mainly to a phase gradient-based coded metasurface antenna array structure and a design method. Background Art

[0002] In modern electronic warfare, the stealth performance of combat platforms such as aircraft, rockets, and ships often directly affects their combat capability and survivability. Various means are used to change the detectable information characteristics of one's own targets, making it possible for enemy equipment to fail to detect them or even mistakenly identify them as other targets to achieve the purpose of "hiding the truth and showing the false."

[0003] At present, most stealth designs for antenna arrays use passive cancellation technology, or load frequency-selective surface antenna covers for filtering, or load metasurface structures around the antenna / floor for wave absorption / phase cancellation... Once such design methods are implemented, the scattering pattern of the antenna is fixed, and it is gradually unable to adapt to today's treacherous wars. This requires further transformation of design ideas and introduction of coding ideas, so that the antenna can switch different scattering beam patterns in the working frequency band and even achieve adjustable scattering beams, achieving the effect of "hiding the truth and showing the false", which is of great research significance for further improving the survivability of one's own equipment.

[0004] The concept of coded metasurface was first proposed by Professor Cui Tiejun's research group at Southeast University in 2014. They introduced the design ideas of "0" and "1" in digital circuits into the design of metasurfaces. Taking 1 bit as an example, by using "0" and "1" to code two units with a phase difference of 180°, the design of metasurfaces is more flexible. After the design of traditional antennas is completed, their radiation performance and scattering characteristics are basically fixed and can only be applied to a single engineering application system. In addition, most of the existing coded metasurface technologies study the RCS reduction of metasurface structures, and do not combine comprehensive antenna analysis. Therefore, based on the ideas of coded metasurfaces and metasurface antennas, the radiation characteristics of antennas and the RCS reduction characteristics are studied separately. While ensuring that the antenna radiation performance is basically unaffected, the effect of dynamically regulating the antenna scattering performance is presented, which is of great significance for the antenna system to adapt to the complex and changeable battlefield situation in the future.

[0005] Based on the idea of ​​coded metasurface and metasurface antenna, the radiation characteristics of the antenna and the RCS reduction characteristics are studied respectively. While ensuring that the antenna radiation performance is basically unaffected, the effect of dynamically controlling the antenna scattering performance is presented, which is of great significance for the antenna system to adapt to the complex and changeable battlefield situation in the future.

[0006] In the prior art, Li B, Liu SB, Shi HY, Yang C, Chen Q, Zhang A X. Planar Phase Gradient Metasurface Antenna With Low RCS[J]. IEEE ACCESS, 2018, 6: 78839-788450, a patch with a non-resonant mode is used as a basic unit, and small sub-arrays of "3×3" with different arrangements are arranged periodically into a specific form of phase gradient, so that the RCS reduction effect in a wider frequency band can be achieved. However, the current stealth design of phase gradient antenna arrays is to load the phase gradient metasurface as an accessory around the antenna, which not only requires the two to be designed separately, but also increases the size of the antenna. Summary of the invention

[0007] Purpose of the invention: In view of the problems existing in the above-mentioned background technology, the present invention provides a phase gradient-based coded metasurface antenna array structure and design method, aiming to ensure its normal radiation characteristics as much as possible while achieving antenna RCS reduction, and at the same time increase the degree of freedom of the scattering pattern through the coded metasurface method.

[0008] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A phase gradient-based coded metasurface antenna array structure comprises a metal patch layer, a first intermediate dielectric layer, a metal floor layer, a second intermediate dielectric layer, a feed network layer, a third intermediate dielectric layer and a DC bias network layer which are sequentially pressed together;

[0010] The metal patch layer includes a plurality of rectangular patch units, and the lower surface of each patch unit is connected to the feed network layer in the vertical direction through a first feed column; the feed network layer adopts a parallel feed network to supply power to the patch unit through a coaxial feeding method; a second feed column is arranged on each side of the first feed column to connect the patch unit and the DC bias network layer; the metal floor layer is provided with a plurality of gaps at corresponding positions for passing the first feed column and the second feed column; the DC bias network layer includes a plurality of mutually parallel straight metal strips, and a bias current is provided to the metal patch layer through the second feed column.

[0011] Furthermore, the rectangular patch unit includes the following two structures;

[0012] (1) It comprises a central patch and a first square ring and a second square ring arranged outward in sequence, and notches of the same length are symmetrically arranged on the upper and lower sides along the y-axis direction of the plane; pin diodes connecting the first square ring and the second square ring are arranged on both sides of the upper and lower notches along the x-axis direction of the plane, and the direction of the pin diode is from the second square ring to the first square ring;

[0013] (2) It includes a central patch and a first square ring and a second square ring arranged outward in sequence, wherein first notches of the same length are symmetrically arranged on the upper and lower sides along the y-axis direction of the plane; second notches of the same length are symmetrically arranged on the left and right sides along the x-axis direction of the plane; and PIN diodes connected to the notches are arranged on the upper and lower sides along the direction of the first notch, and the PIN diodes are in the same direction;

[0014] The coaxial feeding point of the feeding network layer does not coincide with the axis of the central patch. Each pin diode is vertically mapped to the metal strip of the DC bias network layer, and the DC bias network layer provides bias current.

[0015] Furthermore, the feed network layer supplies power to the rectangular patch units through a power divider according to the number of the rectangular patch units.

[0016] Furthermore, the first dielectric layer, the second dielectric layer, and the third dielectric layer are all made of polytetrafluoroethylene F4B material, with a dielectric constant of 2.65 and a loss tangent of 0.001; the metal patch layer, the metal floor layer, the feed network layer, and the DC bias network layer are all made of a material with a conductivity of σ=5.8×10 7 s / m copper material.

[0017] A method for designing the above-mentioned phase gradient-based coded metasurface antenna array structure comprises the following steps:

[0018] Step S1, designing the original theoretical size of the antenna rectangular patch unit based on requirements and theoretical formulas;

[0019] Step S2, using a coaxial feeding method, deriving the preliminary positions of the coaxial metal feeding posts of the two patch units, that is, the distance between the coaxial feeding point and the center point according to the theoretical calculation formula of the coaxial feeding point position, and obtaining the optimal position by simulating and optimizing the parameters;

[0020] Step S3, by adjusting the structural type of the rectangular patch unit and the size and notch position of the square ring in different structures, the cross-polarized scattering phase of the designed coded metasurface antenna array structure in the on-off state of the four diodes satisfies the phase difference of 180°±37°;

[0021] Step S4: By analyzing the impedance matching of the current and the port, the size of the central rectangular patch and the two outer square rings are further adjusted to optimize the radiation characteristics of the coded metasurface antenna array structure;

[0022] Step S5: Based on the rectangular patch unit arrangement of the metal patch layer, a coaxial feeding network is designed using a Wilkinson power divider model, and a corresponding coaxial feeding network structure is designed;

[0023] Step S6: Based on the number of matrix patch units, design a corresponding DC bias network layer to supply power to each switching diode;

[0024] Step S7, combining the metal patch layer structure, the feed network layer and the DC bias network layer for simulation optimization;

[0025] Step S8, the optimized metal patch layer, feed network layer and DC bias network layer are respectively spaced and combined with an intermediate dielectric layer, pressed in sequence, and the first feed column and the second feed column are assembled to obtain the designed coded metasurface antenna array structure.

[0026] Furthermore, the specific method of designing the feed network layer using the Wilkinson power divider model in step S5 is as follows:

[0027] Step S5.1, dividing the rectangular patch unit into m / 4 2*2 first-level small sub-arrays according to the rectangular patch unit specification m*m in the metal patch layer, and equally feeding the antenna units in the first-level small sub-array;

[0028] Step S5.2, further divide the primary small sub-array into m / 16 secondary large sub-arrays of 4*4; perform power division feeding on the secondary large sub-array;

[0029] Step S5.3: perform corner cutting processing on the connection points of the sub-arrays at each level of the feeding network, and dig holes with a radius of 0.5 mm at the corresponding positions of the coaxial metal columns.

[0030] Beneficial effects:

[0031] The phase gradient-based coded metasurface antenna array structure designed in the present invention has the scattering characteristics of the scattered beam that can be flexibly adjusted. It aims to solve the problem that the radiation and scattering characteristics of traditional antennas are basically fixed after the design is completed, and they can only be applied to a single engineering application system and cannot adapt to the current turbulent war situation.

[0032] By referring to the idea of ​​coded metasurface, the on "0" and off "1" of each unit switch diode in the metasurface antenna array are randomly controlled, and the single main lobe scattering beam of the reference antenna is dispersed to other non-threatening angles in real time. While ensuring that the antenna radiation performance is basically not disturbed, the purpose of stealth inside and outside the antenna band can be achieved and different dynamic scattering effects can be presented. This has important research significance in the field of antenna stealth design. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is an overall three-dimensional cross-sectional diagram of the phase gradient-based coded metasurface antenna array of the present invention;

[0034] Figure 2A side view schematic diagram of a phase gradient-based coded metasurface antenna array of the present invention;

[0035] Figure 3 It is a top view of the structure of the first metal patch unit in an embodiment of the present invention;

[0036] Figure 4 is a top view of the structure of the second metal patch unit in an embodiment of the present invention;

[0037] Figure 5 is a comparison curve diagram of the phase gradient metasurface antenna array S11 of the present invention;

[0038] Figure 6 A comparison curve diagram of the gain direction of the phase gradient metasurface antenna array of the present invention;

[0039] Figure 7 This is a single-station RCS comparison curve diagram of the phase gradient metasurface antenna array of the present invention under x-polarization;

[0040] Figure 8 This is a single-station RCS comparison curve diagram of the phase gradient metasurface antenna array of the present invention under y polarization;

[0041] Fig. 9 It is a comparison curve of the dual-station RCS at the scattering resonance point of the phase gradient metasurface antenna array of the present invention under y-polarization. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In this embodiment, an 8*8 metasurface antenna array is used as an example to introduce the specific structure. Figure 1-2 As shown, it includes a metal patch layer 1, a first intermediate dielectric layer 51, a metal floor layer 2, a second intermediate dielectric layer 52, a feed network layer 3, a third intermediate dielectric layer 53 and a DC bias network layer 4 which are pressed together in sequence.

[0044] The metal patch layer 1 includes a plurality of rectangular patch units, and the lower surface of each patch unit is connected to the feed network layer 3 in the vertical direction through the first feed column 7. The feed network layer adopts a parallel feeding network, and according to the number of rectangular patch units, the patch units are powered by coaxial feeding through a power divider. A second feed column 6 is arranged on each side of the first feed column 7, connecting the patch unit and the DC bias network layer in the vertical direction. The metal floor layer is provided with a plurality of gaps at corresponding positions for passing the first feed column and the second feed column. The DC bias network layer includes a plurality of straight metal strips parallel to each other, and a bias current is provided to the metal patch layer through the second feed column.

[0045] like Figure 2 As shown, in this embodiment, the first intermediate dielectric layer 51, the second intermediate dielectric layer 52 and the third intermediate dielectric layer 53 are all made of 120mm*120mm F4B polytetrafluoroethylene material, whose dielectric constant is 2.65 and the loss tangent value is equal to 0.001. The thickness of the first intermediate dielectric layer 51 is 1.6mm, the thickness of the second intermediate dielectric layer 52 is 0.4mm, and the thickness of the third intermediate dielectric layer 53 is 0.4mm. The metal patch layer 1, the metal floor layer 2, the feed network layer 3 and the DC bias network layer 4 all use a conductivity of σ=5.8×10 7 s / m copper material.

[0046] The metal patch layer used in this embodiment includes two structures, which are as follows:

[0047] (1) Figure 3 As shown, it includes a central patch and a first square ring and a second square ring arranged outward in sequence, and notches of the same length L2 are symmetrically arranged on the upper and lower sides along the plane y-axis direction. The outer ring size of the small square ring is W3, and the inner ring size is W2. The outer ring size of the large square ring is W4, and the inner ring size is W5. Pin diodes connecting the first square ring and the second square ring are arranged on both sides of the upper and lower notches along the plane x-axis direction, and the direction of the pin diode is from the second square ring to the first square ring. The antenna adopts a coaxial feeding method, and the distance between the coaxial feeding point and the center point is g.

[0048] (2) Figure 4 As shown, it includes a central patch and a first square ring and a second square ring arranged outward in sequence, and a first notch of the same length L2 is symmetrically arranged on the upper and lower sides along the plane y-axis direction. A second notch of the same length W6 is symmetrically arranged on the left and right sides along the plane x-axis direction. Pin diodes connected to the notch are arranged on the upper and lower sides along the direction of the first notch, and the pin diodes are in the same direction. The antenna adopts a coaxial feeding method, and the distance between the coaxial feeding point and the center point is g1.

[0049] Each pin diode is vertically mapped to the metal strip of the DC bias network layer, and the DC bias network layer provides bias current. The pin diode model used in this embodiment is MACOM MADP-000907-14020, which is equivalent to a 20nH inductor connected in series with a 7Ω resistor in the on state. In the off state, it is equivalent to a 20nH inductor connected in series with a 25fF capacitor.

[0050] In this embodiment, the size parameters of the phase gradient coded metasurface antenna unit are given, as shown in Table 1:

[0051] Table 1 Phase gradient coded metasurface antenna unit size parameters

[0052]

[0053] The following provides a design method for a phase gradient-based coded metasurface antenna array structure, comprising the following steps:

[0054] Step S1, designing the original theoretical size of the antenna rectangular patch unit based on requirements and theoretical formulas.

[0055] Step S2: Because the scattering of the antenna is mainly divided into mode item scattering and structural mode item scattering, in order to avoid the influence of the antenna array feeding network on the antenna RCS, a coaxial feeding method is selected at the lower layer of the antenna. The preliminary position of the coaxial metal feeding column is derived according to the theoretical calculation formula of the coaxial feeding point position, and the optimal position is optimized through simulation.

[0056] Step S3, by adjusting the structural type of the rectangular patch unit and the size and notch position of the square ring in different structures, the designed coding metasurface antenna array structure is made to satisfy the phase difference of 180°±37° for the cross-polarized scattering phase when the four diodes are on and off. Based on this, two resonant double rings with different structures are designed, one of which is a resonant double ring with two openings in the vertical direction, and the four pin tubes are distributed on both sides of the two notches and from the outer ring to the inner ring; the other is a resonant double ring with four openings and two openings in the vertical and horizontal directions respectively, and the four pin tubes are located on the inner and outer rings of the two openings in the vertical direction, and one end of the vertical opening points to the other end of the same ring.

[0057] Step S4: By analyzing the impedance matching of the current and the port, the size of the rectangular patch unit and the outer square ring is further adjusted to optimize the radiation characteristics of the coded metasurface antenna array structure.

[0058] Step S5: According to the 8*8 antenna arrangement, a coaxial feeding network is designed using the Wilkinson power divider model, and a corresponding coaxial feeding network structure is designed. Specifically,

[0059] Step S5.1: First, divide the 64 rectangular patch units into sixteen 2×2 first-level small sub-arrays, and perform four-way equal feeding on the antenna units in the first-level small sub-arrays.

[0060] Step S5.2: further divide the primary small sub-array into four 2×2 secondary large sub-arrays. Perform one-to-four power division feeding on the secondary large sub-array.

[0061] Step S5.3: In order to reduce the line loss in the high-frequency circuit, the connection of each sub-array of the feed network needs to be chamfered. In order to isolate the feed network layer from the coaxial metal column, a concentric ring hole with an inner radius of 0.25 mm and an outer radius of 0.75 mm needs to be dug around the coaxial metal column connecting the radiation patch layer and the feed network layer, wherein the holes are filled with the medium interspersed through each layer, but the holes interspersed through the metal floor layer are filled with air.

[0062] Step S6: designing a corresponding DC bias feed network according to the 64 DC bias points to supply power to the switch pin diode.

[0063] Step S7: Combine the metal patch layer structure, the feed network layer and the DC bias network layer for simulation optimization.

[0064] Step S8, the optimized metal patch layer, feed network layer and DC bias network layer are respectively spaced and combined with an intermediate dielectric layer, pressed in sequence, and the first feed column and the second feed column are assembled to obtain the designed coded metasurface antenna array structure.

[0065] For easier understanding and more intuitive explanation, the present invention is further described in combination with the CST STUDIO 2018 simulation results:

[0066] The curves of return loss of the antenna of the present invention and the reference antenna varying with frequency are simulated and calculated. Figure 5It can be seen that the operating frequency bands of the five designed phase gradient metasurface antenna arrays are basically overlapping, and their resonant bandwidth with S11 less than -10dB covers the 8.2~9.0GHz frequency band, which meets the frequency band requirements for the X-band stealth antenna design. The working resonance point of a single metasurface antenna is around 9.0GHz, and after the 8×8 array, the resonant frequency of the antenna array is shifted 500MHz to a low frequency near 8.5GHz. This is because when forming the array, coaxial metal columns are considered to connect the first metal patch layer with the feed network and the bias network layer. The loading of the coaxial metal columns increases the current flow path, thereby causing the working frequency band of the entire array to shift to a low frequency. Other resonance points with S11 less than -10dB that appear near the antenna operating band are due to the lack of complete matching between the feed network and the antenna. In addition, compared with the two reference antennas, the S11 of the three low RCS layout antenna arrays at the resonant frequency of 8.5GHz all reached below -24dB. From Figure 6 It can also be seen from the gain comparison curves of the five antennas at the resonant point of 8.5GHz that the directional patterns of the phase gradient metasurface antenna arrays in these five states are basically consistent, and the gains at the resonant frequency are all greater than 20dB.

[0067] from Figure 7 It can be seen that compared with the trend that the far-field RCS of the metal plate increases with the increase of frequency, the three low RCS antennas and the two reference antennas all have a scattering absorption peak around 8.5GHz, which is mainly due to the absorption achieved by the 50-ohm terminal matching.

[0068] Figure 8The figure shows the single-station RCS comparison of five antennas. The solid line, dash-dot line and dotted line represent the RCS curves of 00 / 01 / 10 / 11 / 00 / 01 / 10 / 11 layout antenna, 00 / 00 / 01 / 01 / 10 / 10 / 11 layout antenna, and 00 / 00 / 10 / 10 / 01 / 01 / 11 / 11 layout antenna under vertical incidence of y-polarized wave. The triangular dash-dot line and star-dash line represent the far-field RCS curves of different reference antennas. It can be seen that the trends of the two reference antennas are basically the same. When the frequency tends to high frequency, the RCS value also gradually increases. All three phase gradient coded metasurfaces can achieve an RCS reduction effect of more than 6dB in the range of 7.5GHz to 9GHz, and their common scattering resonance point is around 8.3GHz. Among them, the 00 / 01 / 10 / 11 / 00 / 01 / 10 / 11 layout antenna has a minimum RCS value of -14.6dBsm at the scattering resonance point. At this time, the corresponding RCS values ​​of reference antennas 1 and 2 are 3.4dBsm and 2.6dBsm. In comparison, the maximum RCS reduction of a single station of this layout antenna can reach 18dBsm. The lowest RCS value of the 00 / 00 / 01 / 01 / 10 / 10 / 11 / 11 layout antenna at the scattering resonance point is -14.8dBsm. Compared with the reference antenna, its maximum RCS reduction is 18.2dBsm. The lowest RCS value of the 00 / 00 / 10 / 10 / 01 / 01 / 11 / 11 layout antenna at the scattering resonance point is -15.8dBsm. Compared with the reference antenna, its maximum RCS reduction is 19.2dBsm.

[0069] Fig. 9 The following is a comparison of the dual-station RCS curves of the three low RCS antennas and the reference antenna at the scattering resonance point of 8.3GHz. It can be seen that for the reference antenna, the direction with the largest scattered energy is θ=0°, which is the result of the in-phase superposition of all unit scattering factors. For the 00 / 01 / 10 / 11 / 00 / 01 / 10 / 11 layout antenna, the maximum scattered wave is deflected to the θ=35° angle domain, the maximum scattered wave of the 00 / 00 / 01 / 01 / 10 / 10 / 11 / 11 layout antenna is deflected to the θ=12° angle domain, and the maximum scattered wave of the 00 / 00 / 10 / 10 / 01 / 01 / 11 / 11 layout antenna appears in the θ=-25° angle domain. Since the main scattering peaks of the antennas of these three layouts are abnormally scattered to other angle domains to a certain extent, they all obtain the ideal scattering zero point at θ=0°.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A phase gradient-based coded metasurface antenna array structure, characterized in that: It includes a metal patch layer, a first intermediate dielectric layer, a metal floor layer, a second intermediate dielectric layer, a feed network layer, a third intermediate dielectric layer and a DC bias network layer which are pressed together in sequence; The metal patch layer includes a plurality of rectangular patch units, and the lower surface of each patch unit is connected to the feed network layer in a vertical direction through a first feed column; the feed network layer adopts a parallel feed network to supply power to the patch unit through a coaxial feeding method; a second feed column is arranged on each side of the first feed column to connect the patch unit and the DC bias network layer; the metal floor layer is provided with a plurality of gaps at corresponding positions for passing the first feed column and the second feed column; the DC bias network layer includes a plurality of mutually parallel straight metal strips, and a bias current is provided to the rectangular patch unit through the second feed column; The rectangular patch unit includes the following two structures: (1) It comprises a central patch and a first square ring and a second square ring arranged outward in sequence, and notches of the same length are symmetrically arranged on the upper and lower sides along the y-axis direction of the plane; pin diodes connecting the first square ring and the second square ring are arranged on both sides of the upper and lower notches along the x-axis direction of the plane, and the direction of the pin diode is from the second square ring to the first square ring; (2) It includes a central patch and a first square ring and a second square ring arranged outward in sequence, wherein first notches of the same length are symmetrically arranged on the upper and lower sides along the y-axis direction of the plane; second notches of the same length are symmetrically arranged on the left and right sides along the x-axis direction of the plane; and PIN diodes connected to the notches are arranged on the upper and lower sides along the direction of the first notch, and the PIN diodes are in the same direction; The coaxial feeding point of the feeding network layer does not coincide with the axis of the central patch; each pin diode is vertically mapped to the metal strip of the DC bias network layer, and the DC bias network layer provides bias current.

2. According to the phase gradient-based coded metasurface antenna array structure of claim 1, it is characterized in that: The feed network layer supplies power to the rectangular patch units through a power divider according to the number of the rectangular patch units.

3. The phase gradient-based coded metasurface antenna array structure according to claim 1, characterized in that: The first intermediate dielectric layer, the second intermediate dielectric layer, and the third intermediate dielectric layer are all made of polytetrafluoroethylene F4B material, with a dielectric constant of 2.65 and a loss tangent value of 0.001; the metal patch layer, the metal floor layer, the feed network layer, and the DC bias network layer are all made of a conductivity of σ=5.8×10 7 s / m copper material.

4. A method for designing a phase gradient-based coded metasurface antenna array structure as described in any one of claims 1 to 3, characterized in that: The following steps are involved: Step S1, designing the original theoretical size of the antenna rectangular patch unit based on requirements and theoretical formulas; Step S2, using a coaxial feeding method, deriving the preliminary positions of the coaxial metal feeding posts of the two patch units, that is, the distance between the coaxial feeding point and the center point according to the theoretical calculation formula of the coaxial feeding point position, and obtaining the optimal position by simulating and optimizing the parameters; Step S3, by adjusting the structural type of the rectangular patch unit and the size and notch position of the square ring in different structures, the cross-polarized scattering phase of the designed coded metasurface antenna array structure in the on-off state of the four diodes satisfies the phase difference of 180°±37°; from Step S4: By analyzing the impedance matching of the current and the port, the sizes of the rectangular patch and the two square rings in the center of the unit are further adjusted to optimize the radiation characteristics of the coded metasurface antenna array structure; Step S5: Based on the rectangular patch unit arrangement of the metal patch layer, a coaxial feeding network is designed using a Wilkinson power divider model, and a corresponding coaxial feeding network structure is designed; Step S6: Based on the number of matrix patch units, design a corresponding DC bias network layer to supply power to each switch PIN diode; Step S7, combining the metal patch layer structure, the feed network layer and the DC bias network layer for simulation optimization; Step S8, the optimized metal patch layer, feed network layer and DC bias network layer are respectively spaced and combined with an intermediate dielectric layer, pressed in sequence, and the first feed column and the second feed column are assembled to obtain the designed coded metasurface antenna array structure.

5. The design method of a phase gradient-based coded metasurface antenna array structure according to claim 4, characterized in that: The specific method of designing the feed network layer using the Wilkinson power divider model in step S5 is as follows: Step S5.1, dividing the rectangular patch unit into m / 4 2*2 first-level small sub-arrays according to the rectangular patch unit specification m*m in the metal patch layer, and equally feeding the antenna units in the first-level small sub-array; Step S5.2, further divide the primary small sub-array into m / 16 secondary large sub-arrays of 4*4; perform power division feeding on the secondary large sub-array; Step S5.3, the connection points of the sub-arrays at each level of the feed network are chamfered, and a concentric ring hole with an inner radius of 0.25 and an outer radius of 0.75 is dug around the coaxial metal column connecting the radiation patch layer and the feed network layer, wherein the holes are filled with the medium interspersed through each layer, and the holes interspersed through the metal floor layer are filled with air.

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