Arbitrary polarization converter based on time-coded transmission dual-polarization metasurface

Abstract

The present invention relates to an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface, which belongs to the field of artificial electromagnetic metamaterials. n×n metasurface units are arranged in an array in a two-dimensional plane, and each metasurface unit integrates four switching diodes, wherein two switching diodes in the same polarization direction are connected in pairs through metal patches, and the two switching diodes in the same polarization direction are controlled by the same external control circuit, and the switching diodes of different polarizations are independently controlled by different external control circuits. By independently and periodically switching the bias voltage on the switching diode, the equivalent transmission coefficient of the metasurface can be effectively regulated, thereby converting an arbitrarily polarized incident wave into an arbitrarily polarized outgoing wave at fundamental and harmonic frequency points.

Description

Technical Field

[0001] The present invention relates to the field of artificial electromagnetic metamaterials, and in particular to an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface. Background Art

[0002] Polarization is one of the basic properties of electromagnetic waves, and its effective control is crucial in many fields such as scientific research and engineering applications. In recent years, metasurfaces have been widely used to control the polarization characteristics of electromagnetic waves due to their advantages such as low profile, low cost, and easy processing. In order to adapt to the increasingly complex application environment and increasing application needs, the concept of reconfigurable metasurfaces that integrate multiple different electromagnetic functions by loading active devices such as varactors and switching diodes has been proposed. The electromagnetic function of the metasurface can be switched by switching the working state of the active device. Therefore, the same incident electromagnetic wave can be converted into multiple outgoing waves with different polarizations using the same reconfigurable metasurface device.

[0003] However, most of the reconfigurable polarization conversion devices based on metasurfaces reported so far are reflective, and their polarization control functions are often limited to special polarizations such as circular polarization and linear polarization. However, circular polarization and linear polarization only occupy a very small part of all polarization states, which will restrict the application of the polarization conversion device in non-special polarization scenarios.

[0004] Therefore, in order to adapt to application scenarios that require multiple polarization scattering information, such as polarization radar, polarization imaging, and wireless communication systems based on polarization modulation, it is urgent to explore a design scheme that can convert arbitrarily polarized incident electromagnetic waves into arbitrarily polarized transmitted waves. Summary of the invention

[0005] The purpose of the present invention is to provide an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface to convert an arbitrarily polarized incident electromagnetic wave into an arbitrarily polarized transmitted wave.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] An arbitrary polarization converter based on a time-coded transmission dual-polarization metasurface, comprising: n×n metasurface units and two external control circuits;

[0008] n×n metasurface units are arranged in an array in a two-dimensional plane;

[0009] The metasurface unit includes a first metal patch layer, a second metal patch layer, a third metal patch layer and a fourth metal patch layer which are spaced apart from each other from top to bottom;

[0010] The first metal patch layer includes a pair of orthogonal first resonant structures, in which a rectangular metal patch equivalent to a dipole is cut into a middle patch and two side patches of equal length; a switching diode is connected between the middle patch and one side patch, and a switching diode is connected between the middle patch and the other side patch; the orthogonality is the orthogonality of the x-polarization direction and the y-polarization direction;

[0011] The fourth metal patch layer includes a pair of orthogonal second resonant structures, in which a rectangular metal patch equivalent to a dipole in the second resonant structure is cut into two metal patches of different lengths; the longer metal patch is respectively connected to the third metal patch layer and the middle patch arranged in the same direction;

[0012] All side patches arranged along the x-polarization direction in all metasurface units are connected to an external control circuit through the second metal patch layer, and all side patches arranged along the y-polarization direction in all metasurface units are connected to another external control circuit through the second metal patch layer; the first metal patch layer is used to receive incident electromagnetic waves, and the third metal patch is used as a common electrode; the external control circuit is used to periodically provide a bias voltage to two switching diodes in the first resonant structure through the second metal patch layer, change the anisotropy of the metasurface unit, convert arbitrarily polarized incident electromagnetic waves into arbitrarily polarized outgoing electromagnetic waves at fundamental and harmonic frequencies, and radiate them through the fourth metal patch layer.

[0013] Optionally, the first resonant structure includes: a first rectangular metal patch, a second rectangular metal patch and two switching diodes;

[0014] The first rectangular metal patch and the second rectangular metal patch are arranged in parallel; the length of the first rectangular metal patch is greater than the length of the second rectangular metal patch;

[0015] The first rectangular metal patch is equivalent to a dipole, and the second rectangular metal patch is equivalent to a parasitic bandpass structure;

[0016] The first rectangular metal patch is cut into a middle patch and two side patches of equal length; the opposite sides of the middle patch are respectively connected to the anode of a switching diode and the cathode of another switching diode, the anode of one switching diode is connected to one side patch, and the cathode of the other switching diode is connected to the other side patch; both side patches are connected to the second metal patch layer.

[0017] Optionally, the external control circuit is a field programmable gate array, a programmable arbitrary waveform generator or a single-chip microcomputer, which outputs a bias voltage of 0V or 3.3V;

[0018] When the external control circuit outputs a bias voltage of 0V, a switching diode in the first resonant structure is turned on, so that the transmission phase of the metasurface unit is 0°;

[0019] When the external control circuit outputs a bias voltage of 3.3V, another switching diode in the first resonant structure is turned on, making the transmission phase of the metasurface unit 180°.

[0020] Optionally, the second metal patch layer includes: two bias voltage loading components;

[0021] One bias voltage loading component is respectively connected to an external control circuit and two side patches in the first resonant structure arranged along the x-polarization direction, and another bias voltage loading component is respectively connected to another external control circuit and two side patches in the first resonant structure arranged along the y-polarization direction.

[0022] Optionally, the bias voltage loading component includes: a narrowband line, two quarter-wavelength converters and two fan-shaped branch patches;

[0023] A side patch, a quarter-wavelength transformer and a fan-shaped branch patch in the first resonant structure are connected in sequence;

[0024] Another side patch in the first resonant structure, another quarter-wavelength converter, another fan-shaped branch patch and one end of the narrowband line are connected in sequence, and the other end of the narrowband line is connected to an external control circuit.

[0025] Optionally, the side patch in the first metal patch layer is connected to the second metal patch layer through a first metal via;

[0026] The middle patch in the first metal patch layer is connected to the longer metal patch in the fourth metal patch layer in the same polarization direction through the second metal via;

[0027] The third metal patch layer is connected to the longer metal patch in the fourth metal patch layer through the third metal via.

[0028] Optionally, the third metal patch layer is a square metal patch with two circular areas removed;

[0029] The two second metal vias pass through the two circular areas in a one-to-one correspondence, and the metal vias do not contact the third metal patch layer.

[0030] Optionally, the metasurface unit further includes: a first dielectric layer, a prepreg layer, and a second dielectric layer;

[0031] The first metal patch layer, the first dielectric layer, the second metal patch layer, the prepreg layer, the third metal patch layer, the second dielectric layer and the fourth metal patch layer are sequentially connected and arranged from top to bottom.

[0032] Optionally, the metasurface unit is a transmission anisotropic unit.

[0033] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0034] The present invention discloses an arbitrary polarization converter based on a time-coded transmission dual-polarization metasurface, wherein n×n metasurface units are arranged in an array in a two-dimensional plane, and each metasurface unit integrates four switching diodes, wherein two switching diodes in the same polarization direction are connected in pairs through metal patches, and the two switching diodes in the same polarization direction are controlled by the same external control circuit, and the switching diodes of different polarizations are independently controlled by different external control circuits. By independently and periodically switching the bias voltage on the switching diodes, the equivalent transmission coefficient of the metasurface can be effectively regulated, thereby converting an arbitrarily polarized incident wave into an arbitrarily polarized outgoing wave at fundamental and harmonic frequency points. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A schematic structural diagram of an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface provided in an embodiment of the present invention;

[0037] Figure 2 A three-dimensional schematic diagram of a metasurface unit provided in an embodiment of the present invention; wherein: Figure 2 (a) is a schematic diagram of the viewing angle along the +z direction. Figure 2 (b) is a schematic diagram of the viewing angle along the -z direction;

[0038] Figure 3 A schematic diagram of the transmission coefficient of a metasurface unit provided in an embodiment of the present invention under the incidence of an x-polarized electromagnetic wave; wherein: Figure 3 (a) is a schematic diagram of the transmission amplitude. Figure 3 (b) is a schematic diagram of the transmission phase;

[0039] Figure 4 A schematic diagram of the transmission coefficient of a metasurface unit provided in an embodiment of the present invention under the incidence of a y-polarized electromagnetic wave; wherein: Figure 4(a) is a schematic diagram of the transmission amplitude. Figure 4 (b) is a schematic diagram of the transmission phase;

[0040] Figure 5 A schematic diagram of equivalent transmission amplitude and phase at fundamental wave, +1st harmonic wave and +2nd harmonic wave frequency points of a metasurface unit provided by an embodiment of the present invention under periodic bias voltage modulation with a coding number of 6 in all periods;

[0041] Figure 6 A schematic diagram of a test environment provided for an embodiment of the present invention;

[0042] Figure 7 A schematic diagram of test results of an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface provided in an embodiment of the present invention at a fundamental frequency point under the incidence of a left-handed circularly polarized electromagnetic wave;

[0043] Figure 8 A schematic diagram of test results of an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface provided in an embodiment of the present invention at a +1-order harmonic frequency point under the incidence of a 45° linearly polarized electromagnetic wave;

[0044] Fig. 9 A schematic diagram of the test results of an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface provided in an embodiment of the present invention at the +2nd harmonic frequency point under the incidence of a right-handed circularly polarized electromagnetic wave.

[0045] Explanation of symbols: 1 - first metal patch layer, 2 - first dielectric layer, 3 - second metal patch layer, 4 - prepreg layer, 5 - third metal patch layer, 6 - second dielectric layer, 7 - fourth metal patch layer. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0047] The purpose of the present invention is to provide an arbitrary polarization converter based on a time-coded transmission-type dual-polarization metasurface to convert an arbitrarily polarized incident electromagnetic wave into an arbitrarily polarized transmitted wave.

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] An embodiment of the present invention provides an arbitrary polarization converter based on a time-coded transmissive dual-polarized metasurface, as Figure 1-3 shown, which includes: n×n metasurface units and two external control circuits.

[0050] The n×n metasurface units are arranged in an array in a two-dimensional plane. The metasurface unit includes a first metal patch layer 1, a second metal patch layer 3, a third metal patch layer 5, and a fourth metal patch layer 7 that are spaced apart from top to bottom. The first metal patch layer 1 includes a pair of orthogonal first resonant structures. In the first resonant structure, the rectangular metal patch equivalent to a dipole is truncated into an intermediate patch and two side patches of equal length; a switching diode is connected between the intermediate patch and one side patch, and a switching diode is connected between the intermediate patch and the other side patch; the orthogonality is the orthogonality of the x-polarization direction and the y-polarization direction. The fourth metal patch layer 7 includes a pair of orthogonal second resonant structures. In the second resonant structure, the rectangular metal patch equivalent to a dipole is truncated into two metal patches of unequal length for enhancing electromagnetic coupling; the metal patches with longer lengths are respectively connected to the third metal patch layer 5 and the intermediate patch arranged in the same direction.

[0051] All the side patches arranged in the x-polarization direction in all the metasurface units are connected to an external control circuit through the second metal patch layer 3, and all the side patches arranged in the y-polarization direction in all the metasurface units are connected to another external control circuit through the second metal patch layer 3; the first metal patch layer 1 is used to receive incident electromagnetic waves, and the third metal patch is used as a common electrode; the external control circuit is used to periodically provide a bias voltage for the two switching diodes in the first resonant structure through the second metal patch layer 3, change the anisotropy of the metasurface unit, convert an arbitrarily polarized incident electromagnetic wave into an arbitrarily polarized outgoing electromagnetic wave at the fundamental wave and harmonic frequency points, and radiate it out through the fourth metal patch layer 7.

[0052] By periodically switching the bias voltage provided by the external control circuit, a new degree of freedom of regulation in the time dimension is added. Not only can the working frequency point be extended from the fundamental wave to the fundamental wave and harmonic frequency points within the spectrum based on the Fourier transform, but also by adjusting the equivalent transmission amplitude ratio and phase difference of the x-polarization and y-polarization, an arbitrarily polarized incident electromagnetic wave can be converted into an arbitrarily polarized outgoing wave.

[0053] The metasurface unit is a transmissive anisotropic unit, and the arbitrary polarization converter is formed by periodically extending exactly the same transmissive anisotropic unit in the xy two-dimensional plane, and its electromagnetic characteristics are real-time regulated by the external control circuit. Two independent bias voltages are respectively used to regulate the electromagnetic characteristics of the electromagnetic surface in the x-polarization direction and the y-polarization direction, so the switching diodes in different polarization directions support independent control. And the two switching diodes in the same polarization direction are alternately turned on under the periodic regulation of the same external control circuit.

[0054] The external control circuit is a field programmable gate array, a programmable arbitrary waveform generator or a single-chip microcomputer, which outputs a bias voltage of 0V or 3.3V. When the external control circuit outputs a bias voltage of 0V, one of the switch diodes in the first resonant structure is turned on and the other switch diode is turned off, so that the transmission phase of the metasurface unit is 0°. When the external control circuit outputs a bias voltage of 3.3V, another switch diode in the first resonant structure is turned on and the above-mentioned one switch diode is turned off, so that the transmission phase of the metasurface unit is 180°. That is, under the control of the external control circuit, the transmission phase of the metasurface unit along the x-polarization and y-polarization directions can be independently switched between 0° or 180°.

[0055] Exemplarily, the first resonant structure includes: a first rectangular metal patch, a second rectangular metal patch and two switching diodes. The first rectangular metal patch and the second rectangular metal patch are arranged in parallel; the length of the first rectangular metal patch is greater than the length of the second rectangular metal patch. The first rectangular metal patch is equivalent to a dipole, and the second rectangular metal patch is equivalent to a parasitic bandpass structure. The first rectangular metal patch is cut into a middle patch and two side patches of equal length. Setting the two side patches to equal length helps to keep the transmission amplitude equal when switching the working state of the diode; the opposite sides of the middle patch are respectively connected to the anode of a switching diode and the cathode of another switching diode, the anode of one switching diode is connected to one side patch, and the cathode of the other switching diode is connected to the other side patch; both side patches are connected to the second metal patch layer 3.

[0056] Four switching diodes are integrated in the metasurface unit, of which two switching diodes with the same polarization are connected to each other through metal patches. The external control circuit can alternately provide a bias voltage of 0V or 3.3V to the switching diodes. By adjusting the working state of the switching diodes, the transmission phase of the unit can be switched alternately between 0° and 180°. By independently and periodically switching the bias voltage on the switching diodes, the equivalent transmission coefficient of the metasurface can be effectively adjusted, thereby converting an incident wave of arbitrary polarization into an outgoing wave of arbitrary polarization at the fundamental and harmonic frequencies.

[0057] In one example, the second metal patch layer 3 includes: two bias voltage loading components. One bias voltage loading component is respectively connected to an external control circuit and two side patches in the first resonant structure arranged along the x-polarization direction, and the other bias voltage loading component is respectively connected to another external control circuit and two side patches in the first resonant structure arranged along the y-polarization direction.

[0058] The bias voltage loading component includes: a narrowband line, two quarter-wavelength converters and two fan-shaped branch patches. A side patch, a quarter-wavelength converter and a fan-shaped branch patch in the first resonant structure are connected in sequence. Another side patch, another quarter-wavelength converter, another fan-shaped branch patch and one end of the narrowband line in the first resonant structure are connected in sequence, and the other end of the narrowband line is connected to an external control circuit. The quarter-wavelength converter and the fan-shaped branch patch isolate the narrowband line (bias line) from the resonant structure.

[0059] Specifically, the side patches in the first metal patch layer 1 are connected to the second metal patch layer 3 through the first metal via. The middle patch in the first metal patch layer 1 is connected to the longer metal patch in the fourth metal patch layer 7 in the same polarization direction through the second metal via. The third metal patch layer 5 is connected to the longer metal patch in the fourth metal patch layer 7 through the third metal via.

[0060] Reference Figure 2 The third metal patch layer 5 is a square metal patch with two circular areas removed. The two second metal vias pass through the two circular areas one by one, and the metal vias do not contact the third metal patch layer 5.

[0061] The metasurface unit further includes: a first dielectric layer 2 , a prepreg layer 4 and a second dielectric layer 6 . Figure 2 This is a three-dimensional schematic diagram of the transmission anisotropic unit structure designed in this embodiment, in which the first metal patch layer 1, the first dielectric layer 2, the second metal patch layer 3, the semi-cured layer 4, the third metal patch layer 5, the second dielectric layer 6 and the fourth metal patch layer 7 are connected in sequence from top to bottom along the +z direction.

[0062] In one example, the metal patch is made of copper. The side length of the transmission anisotropic unit is 28mm, and both layers of dielectrics are F4B dielectrics with a dielectric constant of 3.5 and a loss tangent of 0.0018. The thickness of the two dielectric substrates is 1.5mm, and the thickness of the four-layer metal structure is 0.018mm. The dielectric constant of the semi-cured sheet layer is 4.2 and the thickness is 0.2mm. The longer rectangular patch in the first metal patch layer is 18.9mm long and 2.2mm wide, and the shorter rectangular patch is 15.9mm long and 2mm wide.

[0063] The working state where the switching diode with a larger coordinate on the x-axis (y-axis) is turned on and the switching diode with a smaller coordinate on the x-axis (y-axis) is turned off is marked as code "0"; the working state where the switching diode with a larger coordinate on the x-axis (y-axis) is turned off and the switching diode with a smaller coordinate on the x-axis (y-axis) is turned on is marked as code "1". The code "X / Y" is used to represent the working state of the unit, where "X" represents the code of x-polarization and "Y" represents the code of y-polarization. Then, under the incidence of x-polarized electromagnetic waves, the transmission coefficients of the unit in the working states of "0 / 0", "0 / 1", "1 / 0" and "1 / 1" are as follows: Figure 3 When the y-polarized electromagnetic wave is incident, the transmission coefficient of the unit in the working states of "0 / 0", "0 / 1", "1 / 0" and "1 / 1" is as follows: Figure 4 As shown. Figure 3 and Figure 4 It can be seen that the transmission coefficient of x / y polarization is only determined by the working state of the switching diode loaded in the x / y polarization direction, and a 180° phase difference can be formed by adjusting the working state of the diode loaded in the corresponding polarization direction.

[0064] Figure 5 It is a schematic diagram of the equivalent transmission amplitude and phase of the anisotropic unit at the fundamental, +1st harmonic and +2nd harmonic frequency points under the modulation of the periodic bias voltage with a coding number of 6 in one cycle. When the number of codes in one cycle is large enough, the phase of the equivalent transmission coefficient can be continuously changed from 0° to 360°, and the equivalent transmission amplitude can be continuously changed from 0 to 1. By switching the bias voltage loaded on the two polarizations, the equivalent transmission amplitude and transmission phase of the two polarizations can be controlled in real time. By adjusting the equivalent transmission amplitude ratio and phase difference of the x-polarization and y-polarization, any polarization can be generated. Figure 3-Figure 5 Amplitude represents the transmission amplitude, Phase represents the transmission phase, and Frequency represents the frequency.

[0065] The experimental verification was carried out in a standard microwave darkroom. The test environment was Figure 6 As shown. Figures 7 to 9 As shown, this embodiment measures the test results along three arbitrary tracks on the Poincare sphere at the fundamental wave, +1st harmonic and +2nd harmonic under the incidence of left-hand circular polarization, 45° linear polarization and right-hand circular polarization electromagnetic waves, where the hollow five-pointed star represents the incident polarization and the hollow circle represents the test polarization. The test conditions include circularly polarized, linearly polarized and elliptically polarized electromagnetic waves, and all test results are highly consistent with the design goals. The present invention only takes these three tracks as an example, and the design method provided by the present invention can be extended to arbitrary polarizations at harmonic frequency points of various orders. Figure 6In the figure, Network Analyzer means network analyzer, Anechoic chamber means microwave dark chamber, Transmitter means transmitter, Receiver means receiver, Metasurface means metasurface, Dual-linearly polarized means dual-linear polarization, FPGA: Field Programmable Gate Array, CP means circular polarization, and LP means linear polarization. Figure 7-Figure 9 S 1 , S 2 , S 3 is the Poincare sphere coordinate system.

[0066] Compared with the prior art, the present invention has the following advantages:

[0067] 1. The present invention loads active devices (switching diodes) to two polarization directions respectively, and designs independent bias circuits for the two polarizations, which is conducive to independent regulation of the transmission coefficients in the two polarization directions. By using the third metal patch layer as a common electrode, it is helpful to reduce the number of required electrodes. In order to make the transmission coefficients of the two polarizations follow the same change law and reduce the electromagnetic crosstalk between the two polarizations, the sizes of the orthogonal rectangular metal patches in the first metal patch layer and the fourth metal patch layer are basically the same. In order to isolate the bias line structure from the resonant structure (the structure for receiving and radiating electromagnetic waves in the first and fourth metal patch layers), the second metal patch layer adopts designs such as a quarter-wavelength transformer and a fan-shaped branch.

[0068] 2. The present invention not only expands the traditional two-dimensional space electromagnetic control to three-dimensional time-space electromagnetic control, but also expands the operating frequency from the fundamental wave to the fundamental wave and harmonic wave frequency points by redistributing the energy distribution in the spectrum.

[0069] 3. The present invention can switch the periodic bias voltage loaded on the x-polarization and y-polarization in real time through an external control circuit, thereby switching the polarization state of the transmitted wave in real time, thereby providing scattering information of multiple polarizations, and then has application prospects in the fields of polarization imaging, polarization radar and polarization communication.

[0070] 4. The metasurface proposed by the present invention has a simple structure, is easy to design, and has a low manufacturing cost. It can be flexibly moved to other target operating frequency bands by means of proportional scaling. The processing of the time-coded metasurface can be completed by conventional printed circuit board processes, and the external control circuit can be composed of programmable devices such as field programmable gate arrays, programmable arbitrary waveform generators, or single-chip microcomputers.

[0071] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0072] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An arbitrary polarization converter based on a time-coded transmission dual-polarization metasurface. It is characterized in that include: n×n metasurface units and two external control circuits; n×n metasurface units are arranged in an array in a two-dimensional plane; The metasurface unit includes a first metal patch layer, a second metal patch layer, a third metal patch layer and a fourth metal patch layer which are spaced apart from each other from top to bottom; The first metal patch layer includes a pair of orthogonal first resonant structures, in which a rectangular metal patch equivalent to a dipole is cut into a middle patch and two side patches of equal length; A switching diode is connected between the middle patch and one side patch, and a switching diode is connected between the middle patch and another side patch; the orthogonality is the orthogonality of the x-polarization direction and the y-polarization direction; The fourth metal patch layer includes a pair of orthogonal second resonant structures, in which a rectangular metal patch equivalent to a dipole in the second resonant structure is cut into two metal patches of different lengths; the longer metal patch is respectively connected to the third metal patch layer and the middle patch arranged in the same direction; All side patches arranged along the x-polarization direction in all metasurface units are connected to an external control circuit through the second metal patch layer, and all side patches arranged along the y-polarization direction in all metasurface units are connected to another external control circuit through the second metal patch layer; the first metal patch layer is used to receive incident electromagnetic waves, and the third metal patch is used as a common electrode; the external control circuit is used to periodically provide a bias voltage to two switching diodes in the first resonant structure through the second metal patch layer, change the anisotropy of the metasurface unit, convert an arbitrarily polarized incident electromagnetic wave into an arbitrarily polarized outgoing electromagnetic wave at the fundamental and harmonic frequency points, and radiate it through the fourth metal patch layer; The first resonant structure includes: a first rectangular metal patch, a second rectangular metal patch and two switching diodes; The first rectangular metal patch and the second rectangular metal patch are arranged in parallel; the length of the first rectangular metal patch is greater than the length of the second rectangular metal patch; The first rectangular metal patch is equivalent to a dipole, and the second rectangular metal patch is equivalent to a parasitic bandpass structure; The first rectangular metal patch is cut into a middle patch and two side patches of equal length; the opposite sides of the middle patch are respectively connected to the anode of a switching diode and the cathode of another switching diode, the anode of one switching diode is connected to one side patch, and the cathode of the other switching diode is connected to the other side patch; both side patches are connected to the second metal patch layer.

2. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 1, It is characterized in that The external control circuit is a field programmable gate array, a programmable arbitrary waveform generator or a single-chip microcomputer, which outputs a bias voltage of 0V or 3.3V; When the external control circuit outputs a bias voltage of 0V, a switching diode in the first resonant structure is turned on, so that the transmission phase of the metasurface unit is 0°; When the external control circuit outputs a bias voltage of 3.3V, another switching diode in the first resonant structure is turned on, making the transmission phase of the metasurface unit 180°.

3. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 1, It is characterized in that The second metal patch layer includes: two bias voltage loading components; One bias voltage loading component is respectively connected to an external control circuit and two side patches in the first resonant structure arranged along the x-polarization direction, and another bias voltage loading component is respectively connected to another external control circuit and two side patches in the first resonant structure arranged along the y-polarization direction.

4. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 3, It is characterized in that The bias voltage loading component includes: a narrowband line, two quarter-wavelength converters and two fan-shaped branch patches; A side patch, a quarter-wavelength transformer and a fan-shaped branch patch in the first resonant structure are connected in sequence; Another side patch in the first resonant structure, another quarter-wavelength converter, another fan-shaped branch patch and one end of the narrowband line are connected in sequence, and the other end of the narrowband line is connected to an external control circuit.

5. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 1, It is characterized in that The side patches in the first metal patch layer are connected to the second metal patch layer through the first metal via; The middle patch in the first metal patch layer is connected to the longer metal patch in the fourth metal patch layer in the same polarization direction through the second metal via; The third metal patch layer is connected to the longer metal patch in the fourth metal patch layer through the third metal via.

6. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 5, It is characterized in that The third metal patch layer is a square metal patch with two circular areas removed; The two second metal vias pass through the two circular areas in a one-to-one correspondence, and the metal vias do not contact the third metal patch layer.

7. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 1, It is characterized in that The metasurface unit further includes: a first dielectric layer, a prepreg layer, and a second dielectric layer; The first metal patch layer, the first dielectric layer, the second metal patch layer, the prepreg layer, the third metal patch layer, the second dielectric layer and the fourth metal patch layer are sequentially connected and arranged from top to bottom.

8. The arbitrary polarization converter based on the time-coded transmission dual-polarization metasurface according to claim 1, It is characterized in that The metasurface unit is a transmission anisotropic unit.

Images