A transmissive linearly polarized rotating surface

Abstract

This application belongs to the field of polarized antenna technology and relates to a transmissive linearly polarized rotating surface, including a polarization conversion array, which comprises multiple polarization conversion units. Each polarization conversion unit includes a dielectric layer, a first transmissive layer, and a second transmissive layer. The first transmissive layer includes four arc-shaped strip-shaped patches spaced apart. One end of each patch is located on one diagonal of the dielectric layer, and the other end is located on the other diagonal. The four patches are centrally symmetrically distributed to form a windmill-like structure. A diode is connected to one corresponding end of two opposing patches, and the diode is located on the diagonal of the dielectric layer. The second transmissive layer is connected to the first transmissive layer, and their structures are identical and orthogonal. Changing the voltage of the diodes allows for the rotational control of the linear polarization. This application can modulate linearly polarized incident waves into linearly polarized waves with different tilt angles.

Description

Technical Field

[0001] This application relates to the field of polarized antenna technology, and in particular to a transmissive linearly polarized rotating surface. Background Technology

[0002] Polarization, as an important fundamental parameter besides amplitude, frequency, and phase of electromagnetic waves, describes the vector characteristics of electromagnetic waves. Because targets exhibit a "polarization shift effect" when illuminated by electromagnetic waves, polarization information can be used to deduce the target's physical properties such as size, attitude, and structure. The application of polarization information in modern radar technology has great potential to enhance radar's detection, anti-jamming, classification, and identification capabilities.

[0003] In existing technologies, to enable radars to acquire and utilize polarization information, the method of adding polarization channels is usually adopted, such as dual-polarization radar and fully polarization radar; however, adding polarization channels means a significant increase in development costs and a significant increase in implementation complexity.

[0004] In recent years, with the development of electromagnetic metasurfaces, a number of research works related to polarization control have emerged. By loading diodes into the metasurface structure, rapid switching between different polarization states can be achieved, with switching speeds reaching the level of hundreds of nanoseconds, which has the potential to achieve intra-pulse and inter-pulse control of radar signals.

[0005] However, most current research focuses on the conversion between special polarization states, such as the conversion of linear polarization to orthogonal linear polarization or the conversion of linear polarization to circular polarization. The number of adjustable polarization states is small, which limits its application in radar scenarios. Summary of the Invention

[0006] Therefore, it is necessary to provide a transmissive linearly polarized rotating surface that can modulate linearly polarized incident waves into linearly polarized waves with different tilt angles to address the aforementioned technical problems.

[0007] A transmissive linearly polarized rotating surface includes: a polarization conversion array, wherein the polarization conversion array includes a plurality of array-distributed polarization conversion units;

[0008] The polarization conversion unit includes: a square dielectric layer, a first transmission layer disposed on top of the dielectric layer, and a second transmission layer disposed at the bottom of the dielectric layer;

[0009] The first transmissive layer includes: four first patches arranged in an arc-shaped strip structure and spaced apart; one end of each first patch is located on one diagonal of the dielectric layer, and the other end extends toward the corner of the dielectric layer and is located on another diagonal of the dielectric layer; the four first patches are centrally symmetrically distributed about the center of the dielectric layer, so that the first transmissive layer forms a windmill-shaped structure; one corresponding end of two opposing first patches is connected by a diode, and the diode is located on the diagonal of the dielectric layer;

[0010] The second transmission layer is connected to the first transmission layer, and the two have the same structure and are orthogonal to each other;

[0011] By changing the voltage of the diode, the state of the diode gradually changes between fully conducting and fully cut off, thereby achieving rotational control of linear polarization.

[0012] In one embodiment, the first transmissive layer further includes four second patches that correspond one-to-one with the four first patches;

[0013] The second patch includes a first part and a second part; both the first part and the second part are strip-shaped structures, and one end of the first part is connected to the middle of the second part, so that the second patch forms a "T" shaped structure.

[0014] The other end of the first part of the second patch is connected to the other end of the corresponding first patch.

[0015] In one embodiment, the first transmissive layer further includes: two third patches;

[0016] Two third patches are respectively disposed on two first patches connected to the diode and correspond one-to-one; one corresponding end of the third patch is connected to the middle of the corresponding first patch, and the other corresponding end extends towards the edge of the dielectric layer;

[0017] An inductor is provided on the third patch.

[0018] In one embodiment, the first portion is a straight strip structure, and the first portion is located on the diagonal of the dielectric layer;

[0019] The second part is an arc-shaped strip structure, and the second part protrudes towards the corner of the dielectric layer.

[0020] In one embodiment, the angle between the length direction of the third patch and any diagonal direction of the dielectric layer is 45°.

[0021] In one embodiment, changing the voltage of the diode to gradually change the state of the diode between fully conducting and fully cut off includes:

[0022] Keep the voltage of the diode on the first transmission layer constant, and change the voltage of the diode on the second transmission layer so that the state of the diode on the second transmission layer gradually changes between fully conducting and fully cut off.

[0023] Alternatively, the voltage of the diode on the second transmission layer can be kept constant, while the voltage of the diode on the first transmission layer can be changed, so that the state of the diode on the first transmission layer gradually changes between fully conducting and fully cut off.

[0024] In one embodiment, it further includes: a polarization reflection array, the polarization reflection array being spaced above the polarization conversion array to form a Fabry-Perot resonant cavity.

[0025] In one embodiment, the polarization reflection array includes: a plurality of array-distributed polarization reflection units;

[0026] The polarized reflection unit includes: a substrate layer and a reflective layer disposed on top of the substrate layer;

[0027] The reflective layer includes multiple spaced arrays of reflective patches, which are strip-shaped to form a fence-like structure.

[0028] In one embodiment, the polarization reflection unit corresponds one-to-one with the polarization conversion unit;

[0029] The substrate layer has a square structure, and the four sides of the substrate layer are parallel to the four sides of the dielectric layer, respectively.

[0030] The two ends of the reflective patch are respectively connected to a set of opposite edges on the top of the substrate layer.

[0031] In one embodiment, the reflective patch is a linear strip structure, with any two reflective patches arranged in parallel and the distance between any two adjacent reflective patches being equal.

[0032] The aforementioned transmissive linearly polarized rotating surface is a polarization time-varying metasurface, which has the following beneficial effects:

[0033] 1) A polarization conversion array (i.e., a polarization control surface, also an amplitude modulation surface) was designed. The first patch is a radial arm with an arc-shaped strip structure, and two first patches are connected by diodes. It has the ability to independently control the orthogonal polarization amplitude. It can control the transmitted wave in any direction by adjusting the amplitude ratio of the orthogonal polarization components of the transmitted electromagnetic wave, and control the transmitted wave into linear polarization with different tilt angles. It realizes the rotational control of the linear polarization tilt angle and the conversion between multiple polarization states, and has the ability to control the polarization state of electromagnetic waves in real time. At the same time, by changing the output voltage of the external control circuit at both ends of the diode in real time, the bias voltage of the diode is controlled in real time, thereby realizing the dynamic control of polarization. The electronically controlled variable polarization control has the advantages of fast control speed (control speed can reach hundreds of ns) and high control accuracy. It can realize the intra-pulse and inter-pulse polarization control of radar signals, and has great application potential in radar systems. In addition, the design of the first patch can have a larger inductance in a limited area, improve angular stability, and facilitate miniaturization.

[0034] 2) A second patch was further designed to generate an equivalent capacitance between adjacent polarization conversion units, thereby changing the equivalent circuit, which is beneficial for accurately controlling the amplitude ratio of quadrature polarization and improving the linear polarization control effect.

[0035] 3) A third patch and inductor were further designed to block the AC signal generated when the metasurface is irradiated.

[0036] 4) Further, based on the design of a polarization conversion array to achieve linear polarization rotational control, a polarization reflection array (i.e., a polarization reflection surface) is designed and spaced apart from the polarization conversion array. The polarization control surface and the polarization reflection surface are cascaded to form a Fabry-Perot resonant cavity. Electromagnetic waves undergo multiple reflections, polarization conversions, and retransmissions between the resonant cavities, which can improve the working bandwidth of the polarization rotation surface, the transmittance of electromagnetic waves, and the energy conversion efficiency. At the same time, it reduces losses (including dielectric loss, reflection loss, diode power consumption, etc.), and the performance is stable within a 10% relative bandwidth, ensuring that the radar detection performance does not degrade. Compared with the existing technology that only achieves polarization conversion at a single frequency point or in an extremely narrow frequency band, this application has obvious bandwidth and energy conversion advantages, which can better match the radar system and increase the degree of freedom for radar target identification methods.

[0037] 5) In addition, unlike most polarization control research that uses a reflective structure, the structure designed in this application is a transmissive structure. When the transmissive polarization control surface is mounted on the antenna aperture and used in conjunction with the radar antenna, it will not cause additional obstruction. Moreover, the energy attenuation can be controlled within 1.5dB and the transmittance is above 87%.

[0038] 6) It should also be noted that this application only needs to be loaded in front of the antenna aperture of the radar system (specifically: loaded as a cladding layer onto the single-polarization radar antenna aperture, so that the original radar antenna and the polarizer together constitute a polarization antenna system), without modifying the antenna system. It can be flexibly disassembled and enriches the information detection dimensions of the single-polarization radar in a low-cost manner, thereby providing a new growth point for improving the radar target identification capability. It has high reliability, balances performance and cost, and is easy to implement in engineering. Attached Figure Description

[0039] Figure 1 This is a three-dimensional schematic diagram of a transmissive linearly polarized rotating surface in one embodiment;

[0040] Figure 2 This is a top view of a polarization conversion unit in a transmissive linearly polarized rotating surface in one embodiment;

[0041] Figure 3 This is a schematic diagram illustrating the principle of a transmission-type linearly polarized rotating surface controlling the linear polarization tilt angle by adjusting the amplitude ratio of the orthogonal polarization components in one embodiment.

[0042] Figure 4 This is a schematic diagram illustrating the principle of improving the working bandwidth and energy transmission efficiency of a transmissive linearly polarized rotating surface by constructing a Fabry-Perot resonant cavity in one embodiment.

[0043] Figure 5 This is a graph showing the variation of the amplitude of the main polarization and cross-polarization transmission coefficients with the resistance value (bias voltage) when the voltage of the diode on the second transmission layer remains constant and the voltage of the diode on the first transmission layer is changed in a polarization conversion array of a transmissive linearly polarized rotating surface in one embodiment.

[0044] Figure 6 In one embodiment, a phase difference diagram between orthogonally polarized waves is generated when the voltage of the diode on the second transmission layer remains constant and the voltage of the diode on the first transmission layer is changed in a polarization conversion array of a transmissive linearly polarized rotating surface.

[0045] Figure 7 In one embodiment, a polarization conversion array of a transmissive linearly polarized rotating surface maintains a constant voltage on the diodes in the second transmissive layer while changing the voltage on the diodes in the first transmissive layer, showing the total transmission coefficient.

[0046] Figure 8 This is a graph showing the change in linear polarization tilt angle when the voltage of the diode on the second transmission layer remains constant and the voltage of the diode on the first transmission layer is changed in a polarization conversion array of a transmissive linearly polarized rotating surface in one embodiment.

[0047] Figure 9This is a diagram showing the transmission performance of a polarization reflection array of a transmissive linearly polarized rotating surface for x-polarized and y-polarized waves in one embodiment.

[0048] Figure 10 This is a diagram showing the reflection performance of a polarization reflection array of a transmissive linearly polarized rotating surface for u-polarized waves and v-polarized waves in one embodiment.

[0049] Figure 11 This is a graph showing the variation of the main polarization transmission coefficient with resistance value (bias voltage) when the voltage of the diode on the second transmission layer is kept constant and the voltage of the diode on the first transmission layer is changed in a transmissive linearly polarized rotating surface in one embodiment.

[0050] Figure 12 This is a graph showing the variation of the cross-polarization transmission coefficient with resistance value (bias voltage) when the voltage of the diode on the second transmission layer is kept constant and the voltage of the diode on the first transmission layer is changed in a transmissive linearly polarized rotating surface in one embodiment.

[0051] Figure 13 In one embodiment, a phase difference diagram between orthogonally polarized waves is generated when the voltage of the diode on the second transmission layer is kept constant and the voltage of the diode on the first transmission layer is changed on a transmissive linearly polarized rotating surface.

[0052] Figure 14 In one embodiment, a transmissive linearly polarized rotating surface maintains a constant voltage on the diode in the second transmissive layer while changing the voltage on the diode in the first transmissive layer, showing the total transmission coefficient.

[0053] Figure 15 This is a graph showing the change in linear polarization tilt angle when the voltage of the diode on the second transmission layer is kept constant and the voltage of the diode on the first transmission layer is changed in a transmissive linearly polarized rotating surface according to one embodiment.

[0054] Figure 16 This is a graph showing the variation of the main polarization transmission coefficient with resistance value (bias voltage) when the voltage of the diode on the first transmission layer is kept constant and the voltage of the diode on the second transmission layer is changed in a transmissive linearly polarized rotating surface in one embodiment.

[0055] Figure 17 This is a graph showing the variation of the cross-polarization transmission coefficient with resistance value (bias voltage) when the voltage of the diode on the first transmission layer is kept constant and the voltage of the diode on the second transmission layer is changed in a transmissive linearly polarized rotating surface in one embodiment.

[0056] Figure 18In one embodiment, a phase difference diagram between orthogonally polarized waves is generated when the voltage of the diode on the first transmission layer remains constant and the voltage of the diode on the second transmission layer is changed on a transmissive linearly polarized rotating surface.

[0057] Figure 19 In one embodiment, a transmissive linearly polarized rotating surface maintains a constant voltage on the diode in the first transmissive layer and changes the voltage on the diode in the second transmissive layer, showing the total transmission coefficient.

[0058] Figure 20 This is a graph showing the change in linear polarization tilt angle when the voltage of the diode on the first transmission layer remains constant and the voltage of the diode on the second transmission layer is changed in a transmissive linearly polarized rotating surface according to one embodiment.

[0059] Figure 21 This is a distribution diagram of the polarization state of a y-polarized electromagnetic wave on a Poincaré sphere after being modulated by a transmissive linearly polarized rotating surface, as shown in one embodiment.

[0060] Figure label:

[0061] Polarization conversion unit a; dielectric layer 11; first transmission layer 12, first patch 121, second patch 122, third patch 123, inductor 124, diode 125; second transmission layer 13;

[0062] Polarized reflective unit b; substrate layer 21; reflective layer 22;

[0063] Incident wave Ey; transmitted wave T; reflected wave F. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0065] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0066] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this application, "multiple sets" means at least two sets, such as two sets, three sets, etc., unless otherwise explicitly specified.

[0067] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0068] Furthermore, the technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this application.

[0069] This application provides a transmissive linearly polarized rotating surface, such as Figure 1 and Figure 2 As shown, in one embodiment, it includes: a polarization conversion array.

[0070] The polarization conversion array includes multiple array-distributed polarization conversion units, each of which includes a dielectric layer, a first transmission layer, and a second transmission layer.

[0071] The dielectric layer is a supporting component that provides loading positions for the first and second transmission layers; the dielectric layer has a square structure.

[0072] The first transmissive layer is located on top of the dielectric layer and includes: four first patches, four second patches, two third patches, two inductors, and one diode.

[0073] The first patch has an arc-shaped strip structure, with one end located on one diagonal of the dielectric layer and the other end extending towards the corner of the dielectric layer and located on the other diagonal of the dielectric layer. The first patch protrudes towards the edge of the dielectric layer. The four first patches are evenly spaced and are centrally symmetrical about the center of the dielectric layer, so that the first transmission layer forms a windmill-shaped structure.

[0074] The second patch includes: a first part and a second part; both the first part and the second part are strip-shaped structures, and one end of the first part is connected to the middle of the second part so that the second patch forms a "T" shape; four second patches correspond one-to-one with four first patches, and the other end of the first part on the second patch is connected to the other end of the corresponding first patch.

[0075] The third patch has a strip-shaped structure. The two third patches are respectively disposed on the two first patches connected to the diode and correspond one-to-one. One corresponding end of the two third patches is connected to the middle of the corresponding first patch, and the other corresponding end extends towards the edge of the dielectric layer to serve as a feed line.

[0076] The inductor corresponds one-to-one with the third patch, and the inductor is located on the corresponding third patch.

[0077] The diode is positioned between corresponding ends of two opposing first patches (with a gap between corresponding ends of the other two opposing first patches), and is located diagonally on the dielectric layer. The two ends of the diode are connected to an external control circuit (specifically, existing technology) to change the diode's voltage. Specifically, the diode can be a PIN diode.

[0078] The second transmission layer is located at the bottom of the dielectric layer and is connected to the first transmission layer (the specific connection method belongs to the prior art, such as: metallized via). The second transmission layer and the first transmission layer have the same structure and are orthogonal to each other.

[0079] Preferably, the first part is a straight strip structure and is located on the diagonal of the dielectric layer; the second part is an arc-shaped strip structure that is symmetrical about the first part and protrudes towards the corner of the dielectric layer; the above arrangement can ensure the realization of polarization control in the xy direction and polarization control in the uv direction.

[0080] More preferably, the angle between the length direction of the third patch and any diagonal direction of the dielectric layer is 45° to ensure good physical isolation and achieve dual polarization.

[0081] More preferably, the diodes in the first and second transmission layers are of the same type to ensure symmetry.

[0082] In this embodiment, orthogonal polarization refers to the electric field vector directions of a pair of electromagnetic waves being perpendicular to each other. Here, two pairs of orthogonal polarized waves are defined: one pair refers to electromagnetic waves with polarization directions along the x and y directions, denoted as xy polarized waves; the other pair refers to electromagnetic waves with polarization directions along the u and v directions, denoted as uv polarized waves. The angle between the xy and uv directions is 45°. The xy polarized wave can be further decomposed into uv polarized waves.

[0083] Any polarized wave can be represented by mutually orthogonal polarized waves. When the amplitude of the orthogonal polarized waves is changed while the phase difference between them remains constant, the tilt angle of the composite polarization will change, which manifests as a rotation of the linear polarization azimuth angle (defined as twice the tilt angle).

[0084] By changing the voltage of the diode, the state of the diode gradually changes between fully conducting and fully cut off, thus achieving rotational control of linear polarization. Specifically, the voltage of the diode on the first transmission layer is kept constant (i.e., the diode remains open), and the voltage of the diode on the second transmission layer is changed, causing the state of the diode on the second transmission layer to gradually change between fully conducting and fully cut off, resulting in a gradual increase in the equivalent resistance and achieving rotational control of linear polarization; or, the voltage of the diode on the second transmission layer is kept constant (i.e., the diode remains open), and the voltage of the diode on the first transmission layer is changed, causing the state of the diode on the first transmission layer to gradually change between fully conducting and fully cut off, resulting in a gradual increase in the equivalent resistance and achieving rotational control of linear polarization.

[0085] By changing the bias voltage across the PIN diode, the PIN diode can accurately represent different resistance values, thereby altering the equivalent circuit of the polarization conversion array, changing the equivalent impedance of the metasurface, and consequently changing the amplitude ratio of the horizontal to vertical polarization components in a pair of orthogonal polarized waves. This causes the amplitude ratio between the orthogonal polarization components to change after the electromagnetic wave passes through the polarization conversion array, resulting in changes in the intensity and direction of the electric field after vector synthesis. Consequently, the polarization state of the synthesized electromagnetic wave also changes, achieving real-time, near-continuous control of the amplitude ratio of orthogonal polarized waves. The equidistant linear polarization azimuth angle control effect can modulate the linearly polarized wave into a near-equatorial orbit (polarization state distributed along the equator on the Poincaré sphere) linear polarization that covers half of the equatorial orbit. By selecting an appropriate bias voltage, the tilt angle of the transmitted wave polarization state can be changed at equal intervals, achieving the effect of linear polarization rotation.

[0086] like Figure 3 As shown, taking the incident wave as a linearly polarized wave in the y-direction as an example, after being modulated by a linearly polarized rotating surface, the transmitted wave can be represented by the Jones matrix as follows:

[0087]

[0088] Among them, t αβ This represents the transmission coefficient (transmission coefficient) that converts a beta-polarized wave into an α-polarized wave upon incident incidence. Both α and β can take the values ​​x or y, and here t... yy =t uu +t vv t xy =t uu -t vvx and y are a pair of orthogonal polarized waves, u and v are a pair of orthogonal polarized waves, and uv rotates 45° clockwise relative to x and y.

[0089] Typically, if the transmitted wave is elliptically polarized, then the angle t (tilt angle) between the principal axis of the ellipse and the y-axis can be expressed as:

[0090]

[0091] Among them, f xy =arg(t) yy )-arg(t xy ).

[0092] Therefore, by adjusting the transmission coefficients of the main polarization and cross-polarization, the tilt angle of linear polarization can be controlled. Furthermore, the phase difference between the orthogonal polarization components should be as consistent as possible to ensure that the synthesized polarized wave is linearly polarized.

[0093] In another embodiment, the system further includes a polarization reflection array, spaced above the polarization conversion array to form a Fabry-Perot resonant cavity. Polarization components that would otherwise be unable to pass through the polarization conversion array are converted into orthogonally polarized waves by the polarization reflection array and reflected back to the polarization conversion array. At this point, based on the transmissivity of the polarization conversion array to orthogonal polarized waves, the reflected polarization waves can pass through the polarization conversion array significantly. It should be noted that the spacing between the polarization reflection array and the polarization conversion array is prior art. For example, an air layer may be placed between the polarization reflection array and the polarization conversion array, and a non-metallic support column may be provided in the air layer; or a foam layer may be placed between the polarization reflection array and the polarization conversion array.

[0094] Preferably, the polarization reflection array includes: a plurality of arrayed polarization reflection units; the polarization reflection unit includes: a substrate layer and a reflective layer disposed on top of the substrate layer; the reflective layer includes a plurality of spaced arrayed reflective patches, the reflective patches being strip-shaped structures, so that the reflective layer forms a fence-like structure.

[0095] More preferably, the polarization reflection unit and the polarization conversion unit correspond one-to-one. The substrate layer has a square structure, and the four sides of the substrate layer are parallel to the four sides of the dielectric layer. The two ends of the reflective patch are connected to a pair of opposite sides at the top of the substrate layer to filter incident waves from different directions, allowing only incident waves perpendicular to the length direction of the reflective patch to pass through; for example, Figure 1 The polarization reflection unit in the image only has partial reflection function for uv orthogonally polarized waves.

[0096] More preferably, the reflective patch is a linear strip structure, with any two reflective patches arranged in parallel and the distance between any two adjacent reflective patches being equal, so that the reflective layer has different filtering effects on polarized waves in different directions. Specifically, it has the function of blocking the transmission of polarized waves parallel to the reflective patch, while it has a good transmission effect on polarized waves perpendicular to the reflective patch, and it has a partial reflection effect on polarized waves at a 45° angle to the reflective patch.

[0097] In this embodiment, as Figure 4 As shown, due to factors such as electromagnetic wave reflection and active device losses, the loss is relatively large and the transmittance is low. A Fabry-Pérot resonant cavity is constructed. According to the Fabry-Pérot (FP) resonance principle, the polarization reflection array has a partial reflection function for orthogonally polarized waves (specifically uv-polarized waves). The electromagnetic wave undergoes multiple reflections, polarization conversions, and retransmissions between the resonant cavities. Finally, the transmittance of the incident wave after passing through the linearly polarized rotating surface is effectively improved. Furthermore, the above process can effectively reduce the differences at different frequency points, thereby further improving the operating bandwidth.

[0098] It should be noted that the first transmission layer, the second transmission layer, and the reflective layer are all made of metallic materials, while the dielectric layer and the substrate layer are all made of non-metallic materials.

[0099] The aforementioned transmissive linearly polarized rotating surface is a polarization time-varying metasurface, which has the following beneficial effects:

[0100] 1) A polarization conversion array (i.e., a polarization control surface, also an amplitude modulation surface) was designed. The first patch is a radial arm with an arc-shaped strip structure, and two first patches are connected by diodes. It has the ability to independently control the orthogonal polarization amplitude. It can control the transmitted wave in any direction by adjusting the amplitude ratio of the orthogonal polarization components of the transmitted electromagnetic wave, and control the transmitted wave into linear polarization with different tilt angles. It realizes the rotational control of the linear polarization tilt angle and the conversion between multiple polarization states, and has the ability to control the polarization state of electromagnetic waves in real time. At the same time, by changing the output voltage of the external control circuit at both ends of the diode in real time, the bias voltage of the diode is controlled in real time, thereby realizing the dynamic control of polarization. The electronically controlled variable polarization control has the advantages of fast control speed (control speed can reach hundreds of ns) and high control accuracy. It can realize the intra-pulse and inter-pulse polarization control of radar signals, and has great application potential in radar systems. In addition, the design of the first patch can have a larger inductance in a limited area, improve angular stability, and facilitate miniaturization.

[0101] 2) A second patch was further designed to generate an equivalent capacitance between adjacent polarization conversion units, thereby changing the equivalent circuit, which is beneficial for accurately controlling the amplitude ratio of quadrature polarization and improving the linear polarization control effect.

[0102] 3) A third patch and inductor were further designed to block the AC signal generated when the metasurface is irradiated.

[0103] 4) Further, based on the design of a polarization conversion array to achieve linear polarization rotational control, a polarization reflection array (i.e., a polarization reflection surface) is designed and spaced apart from the polarization conversion array. The polarization control surface and the polarization reflection surface are cascaded to form a Fabry-Perot resonant cavity. Electromagnetic waves undergo multiple reflections, polarization conversions, and retransmissions between the resonant cavities, which can improve the working bandwidth of the polarization rotation surface, the transmittance of electromagnetic waves, and the energy conversion efficiency. At the same time, it reduces losses (including dielectric loss, reflection loss, diode power consumption, etc.), and the performance is stable within a 10% relative bandwidth, ensuring that the radar detection performance does not degrade. Compared with the existing technology that only achieves polarization conversion at a single frequency point or in an extremely narrow frequency band, this application has obvious bandwidth and energy conversion advantages, which can better match the radar system and increase the degree of freedom for radar target identification methods.

[0104] 5) In addition, unlike most polarization control research that uses a reflective structure, the structure designed in this application is a transmissive structure. When the transmissive polarization control surface is mounted on the antenna aperture and used in conjunction with the radar antenna, it will not cause additional obstruction. Moreover, the energy attenuation can be controlled within 1.5dB and the transmittance is above 87%.

[0105] 6) It should also be noted that this application only needs to be loaded in front of the antenna aperture of the radar system (specifically: loaded as a cladding layer onto the single-polarization radar antenna aperture, so that the original radar antenna and the polarizer together constitute a polarization antenna system), without modifying the antenna system. It can be flexibly disassembled and enriches the information detection dimensions of the single-polarization radar in a low-cost manner, thereby providing a new growth point for improving the radar target identification capability. It has high reliability, balances performance and cost, and is easy to implement in engineering.

[0106] When the voltage of the diode on the second transmission layer remains constant while the voltage of the diode on the first transmission layer is changed, the transmission performance (including transmission characteristics and polarization control capability) of the polarization conversion array for orthogonally polarized electromagnetic waves is analyzed. The results are as follows: Figures 5 to 8 As shown.

[0107] like Figure 5 As shown, T11 represents the transmission coefficient of the main polarization component (y-polarization), T21 represents the transmission coefficient of the cross-polarization component (x-polarization), and the values ​​in parentheses after T11 and T21 are the resistance values ​​of the PIN diode in the first transmission layer. Figure 5It can be seen that after the electromagnetic wave passes through the single-layer polarization conversion array structure, the amplitude of the orthogonal polarization component is modulated separately, and it shows different trends as the diode resistance value changes. Among them, the amplitude of the main polarization component increases with the increase of the resistance value, while the amplitude of the cross polarization component decreases with the increase of the resistance value.

[0108] like Figure 6 As shown, R U This represents the resistance of the first transmission layer. The diagram shows 10 different resistance values ​​for the first transmission layer. Figure 6 It can be seen that after electromagnetic waves pass through this structure, there is a phase difference of about 180° between the orthogonal polarization components.

[0109] like Figure 7 As shown, R U This represents the resistance of the first transmission layer. The diagram shows 10 different resistance values ​​for the first transmission layer. Figure 7 It is known that the transmittance of electromagnetic waves through a single-layer polarization conversion array is low, with a minimum of about 70%.

[0110] like Figure 8 As shown, R U This represents the resistance of the first transmission layer. The diagram shows 10 different resistance values ​​for the first transmission layer. Figure 8 It can be seen that the single-layer polarization conversion array structure can change the tilt angle of the linear polarization wave within the range of [-45°, 0]. According to the structural symmetry, when the bias voltage across the first transmission layer PIN diode is kept constant and the bias voltage across the second transmission layer PIN diode is changed in real time, the tilt angle of the linear polarization wave can vary within the range of [0, 45°].

[0111] The transmission performance of the polarization reflection array for orthogonally polarized waves was analyzed, and the results are as follows: Figure 9 As for Figure 10 As shown, T yy With T xy R represents the transmission coefficients of the y-polarized component and the x-polarized component when the incident wave is y-polarized, respectively. uu With R vu Let represent the reflection coefficients of the u-polarized and v-polarized components, respectively, when the incident wave is u-polarized. Figure 9 and Figure 10 It can be seen that the incident wave is polarized in the y direction and is perpendicular to the metal grid, and the electromagnetic wave with orthogonal polarization components propagates in the Fabry-Perot resonant cavity.

[0112] To further verify that this application has good variable polarization function, simulation experiments were conducted using CST software in conjunction with MATLAB software to examine the polarization control capability, bandwidth and energy transmission performance of the linearly polarized rotating surface composed of a polarization conversion array and a polarization reflection array.

[0113] When the voltage of the diode on the second transmission layer remains constant while the voltage of the diode on the first transmission layer is changed on the transmissive linearly polarized rotating surface, the transmission characteristics and polarization modulation capability of the linearly polarized rotating surface for transmitted waves are analyzed. The results are as follows: Figures 11 to 15 As shown, T11 represents the transmission coefficient of the main polarization component (y-polarization), T21 represents the transmission coefficient of the cross-polarization component (x-polarization), and the values ​​in parentheses after T11 and T21 are the resistance values ​​of the PIN diode of the first transmission layer, R. U This represents the resistance of the first transmission layer. The diagram shows 10 different resistance values ​​for the first transmission layer. Figures 11 to 15 It can be seen that after electromagnetic waves irradiate the linearly polarized rotating surface, as the bias voltage across the first transmission layer decreases, the corresponding PIN diode changes from a fully conducting state (corresponding to a resistance value of 1Ω) to a cutoff state (corresponding to a resistance value of 2kΩ). At this time, the transmittance of the main polarized electromagnetic wave component gradually increases, while the transmittance of the cross-polarized electromagnetic wave component gradually decreases. During the change of resistance value, the phase difference between the two orthogonal polarized components remains basically at -180°, and the tilt angle of the transmitted wave varies within the range of [-45°, 0]. Compared with the control effect of a single-layer polarization conversion array structure, in the frequency range of 9.1GHz-10.1GHz, the tilt angle change trend obtained after control by the linearly polarized rotating surface is more gradual, exhibiting more stable broadband performance, and the transmittance increases from 70% to 90%.

[0114] When the voltage of the diode on the first transmission layer of the transmissive linearly polarized rotating surface remains constant while the voltage of the diode on the second transmission layer is changed, the transmission characteristics and polarization modulation capability of the linearly polarized rotating surface for transmitted waves are analyzed. The results are as follows: Figures 16 to 20 As shown, T11 represents the transmission coefficient of the main polarization component (y-polarization), T21 represents the transmission coefficient of the cross-polarization component (x-polarization), and the values ​​in parentheses after T11 and T21 are the resistance values ​​of the PIN diode of the first transmission layer, R. V This represents the resistance of the second transmission layer. The diagram shows 10 different resistance values ​​for the second transmission layer. Figures 16 to 20 It can be seen that when the bias voltage at both ends of the second transmission layer of the linearly polarized rotating surface is changed, the phase difference between the orthogonal polarization components remains near 0°, and the modulation effect is manifested as the tilt angle changing in the range of [0, 45°], and the transmittance is increased to 87%.

[0115] like Figure 21 As shown, by sequentially adjusting the bias voltages across the diodes on the first and second transmission layers, a linear polarization rotation effect with 5° tilt angles can be obtained, resulting in the distribution trajectory of the corresponding polarization states on the Poincaré sphere. It can be seen that the linearly polarized incident wave can be modulated into near-orbital linear polarization that covers half of the equatorial orbit.

[0116] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0117] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A transmissive linearly polarized rotating surface, characterized in that, include: A polarization conversion array, comprising a plurality of array-distributed polarization conversion units; The polarization conversion unit includes: a square dielectric layer, a first transmission layer disposed on top of the dielectric layer, and a second transmission layer disposed at the bottom of the dielectric layer; The first transmissive layer includes: four first patches arranged in an arc-shaped strip structure and spaced apart; one end of each first patch is located on one diagonal of the dielectric layer, and the other end extends toward the corner of the dielectric layer and is located on another diagonal of the dielectric layer; the four first patches are centrally symmetrically distributed about the center of the dielectric layer, so that the first transmissive layer forms a windmill-shaped structure; one corresponding end of two opposing first patches is connected by a diode, and the diode is located on the diagonal of the dielectric layer; The second transmission layer is connected to the first transmission layer, and the two have the same structure and are orthogonal to each other; By changing the voltage of the diode, the state of the diode gradually changes between fully conducting and fully cut off, thereby achieving rotational control of linear polarization.

2. The transmissive linearly polarized rotating surface according to claim 1, characterized in that, The first transmissive layer further includes: four second patches that correspond one-to-one with the four first patches; The second patch includes a first part and a second part; both the first part and the second part are strip-shaped structures, and one end of the first part is connected to the middle of the second part, so that the second patch forms a "T" shaped structure. The other end of the first part of the second patch is connected to the other end of the corresponding first patch.

3. The transmissive linearly polarized rotating surface according to claim 2, characterized in that, The first transmissive layer further includes: two third patches; Two third patches are respectively disposed on two first patches connected to the diode and correspond one-to-one; one corresponding end of the third patch is connected to the middle of the corresponding first patch, and the other corresponding end extends towards the edge of the dielectric layer; The third patch is equipped with an inductor.

4. The transmissive linearly polarized rotating surface according to claim 3, characterized in that, The first part is a straight strip structure, and the first part is located on the diagonal of the dielectric layer; The second part is an arc-shaped strip structure, and the second part protrudes towards the corner of the dielectric layer.

5. A transmissive linearly polarized rotating surface according to claim 4, characterized in that, The angle between the length direction of the third patch and any diagonal direction of the dielectric layer is 45°.

6. A transmissive linearly polarized rotating surface according to claim 5, characterized in that, Changing the voltage of the diode to gradually change its state between fully conducting and fully cut off includes: Keep the voltage of the diode on the first transmission layer constant, and change the voltage of the diode on the second transmission layer so that the state of the diode on the second transmission layer gradually changes between fully conducting and fully cut off. Alternatively, the voltage of the diode on the second transmission layer can be kept constant, while the voltage of the diode on the first transmission layer can be changed, so that the state of the diode on the first transmission layer gradually changes between fully conducting and fully cut off.

7. A transmissive linearly polarized rotating surface according to any one of claims 1 to 6, characterized in that, Also includes: A polarization reflection array is spaced above the polarization conversion array to form a Fabry-Perot resonant cavity.

8. A transmissive linearly polarized rotating surface according to claim 7, characterized in that, The polarization reflection array includes: a plurality of polarization reflection units distributed in an array; The polarized reflection unit includes: a substrate layer and a reflective layer disposed on top of the substrate layer; The reflective layer includes multiple spaced arrays of reflective patches, which are strip-shaped to form a fence-like structure.

9. A transmissive linearly polarized rotating surface according to claim 8, characterized in that, Each polarization reflection unit corresponds to one polarization conversion unit; The substrate layer has a square structure, and the four sides of the substrate layer are parallel to the four sides of the dielectric layer, respectively. The two ends of the reflective patch are respectively connected to a set of opposite edges on the top of the substrate layer.

10. A transmissive linearly polarized rotating surface according to claim 9, characterized in that, The reflective patch has a linear strip structure, with any two reflective patches arranged in parallel and the distance between any two adjacent reflective patches being equal.

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