Transmission-type linearly polarized rotating surface

Abstract

The invention belongs to the technical field of polarized antennas, and relates to a transmission-type linear polarization rotating surface, which comprises a polarization conversion array, and the polarization conversion array comprises a plurality of polarization conversion units. The polarization conversion unit comprises a dielectric layer, a first transmission layer and a second transmission layer; the first transmission layer comprises four first patches which are of an arc-shaped strip-shaped structure and are distributed at intervals; one end of the first patch is arranged on one diagonal line of the dielectric layer, and the other end of the first patch is arranged on the other diagonal line of the dielectric layer; the four first patches are distributed in a central symmetry manner, so that the first transmission layer forms a windmill-shaped structure; corresponding ends of the two opposite first patches are connected through a diode, and the diode is arranged on the diagonal line of the dielectric layer; the second transmission layer and the first transmission layer are connected, have the same structure and are mutually orthogonal; and the voltage of the diode is changed to realize rotation regulation and control of linear polarization. According to the invention, the linearly polarized incident waves can be regulated into linearly polarized waves with different inclination angles.

Description

Technical Field

[0001] The present application relates to the technical field of polarized antennas, and in particular to a transmissive linearly polarized rotating surface. Background Art

[0002] Polarization, as an important basic parameter other than the amplitude / frequency / phase of electromagnetic waves, describes the vector characteristics of electromagnetic waves. Since a target will experience a "polarization effect" when it is irradiated by electromagnetic waves, the polarization information can be used to invert the target's physical properties such as size, posture and structure. The application of polarization information in modern radar technology has great potential to improve radar's detection, anti-interference, classification and recognition capabilities.

[0003] In the prior art, in order to enable the radar to have a certain ability to obtain and utilize polarization information, the method of adding polarization channels is usually adopted, such as dual-polarization radar and full-polarization radar; however, adding polarization channels means a significant increase in research and 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 in the metasurface structure, fast switching between different polarization states can be achieved. The switching speed can reach hundreds of nanoseconds, which has the potential to achieve intra-pulse and inter-pulse control of radar signals.

[0005] However, most current research work focuses on the conversion between special polarization states, such as the conversion of linear polarization to orthogonal linear polarization or linear polarization to circular polarization. There are few adjustable polarization states, which limits its application in radar scenarios. Summary of the invention

[0006] Based on this, it is necessary to provide a transmission-type linearly polarized rotating surface to address the above-mentioned technical problems, which can control the linearly polarized incident wave into a linearly polarized wave with different inclination angles.

[0007] A transmission type linear polarization rotating surface comprises: a polarization conversion array, wherein the polarization conversion array comprises a plurality of polarization conversion units distributed in an array;

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

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

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

[0011] The voltage of the diode is changed so that the state of the diode gradually changes between full conduction and full cutoff, so as to realize the rotation regulation of linear polarization.

[0012] In one embodiment, the first transmission layer further includes: four second patches corresponding to the four first patches one by one;

[0013] The second patch includes: a first part and a second part; the first part and the second part are both 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 on the second patch is connected to the other end of the corresponding first patch.

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

[0016] The two third patches are respectively arranged on the two first patches connected to the diodes and correspond to each other one by one; one corresponding end of the third patch is connected to the middle of the corresponding first patch, and the other corresponding end extends toward the edge direction of the dielectric layer;

[0017] The third patch is provided with an inductor.

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

[0019] The second portion is an arc-shaped strip structure, and the second portion protrudes toward the corner end 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 so that the state of the diode gradually changes between fully turned on and fully turned off includes:

[0022] Keeping the voltage of the diode on the first transmission layer unchanged, and changing 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 turned on and fully turned off;

[0023] Or, the voltage of the diode on the second transmission layer is kept unchanged, and the voltage of the diode on the first transmission layer is changed, so that the state of the diode on the first transmission layer gradually changes between fully turned on and fully turned off.

[0024] In one embodiment, it further includes: a polarization reflection array, wherein the polarization reflection array is arranged above the polarization conversion array at intervals to form a Fabry-Perot resonant cavity.

[0025] In one embodiment, the polarization reflection array comprises: a plurality of polarization reflection units distributed in an array;

[0026] The polarization reflection unit comprises: a substrate layer and a reflection layer arranged on the top of the substrate layer;

[0027] The reflective layer includes a plurality of reflective patches distributed in an interval array, and the reflective patches are strip-shaped structures, so that the reflective layer forms a fence-shaped structure.

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

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

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

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

[0032] The above-mentioned transmission type linear polarization rotating surface is a polarization time-varying control metasurface, which has the following beneficial effects:

[0033] 1) A polarization conversion array (i.e., polarization control surface, also amplitude modulation surface) is designed. The first patch is a radiation arm of an arc-shaped strip structure and two first patches are connected by a diode. It has the ability to independently control the orthogonal polarization amplitude. It can control the transmitted wave in any direction by controlling the amplitude ratio of the orthogonal polarization components of the transmitted electromagnetic wave, and control the transmitted wave to a linear polarization with different inclination angles, thereby realizing the rotation control of the linear polarization inclination angle and the conversion between multiple polarization states. It has the ability to control the polarization state of the electromagnetic wave 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 dynamic polarization control. The electrically controlled variable polarization control has the advantages of fast control speed (control speed can reach hundreds of nanoseconds) and high control accuracy. It can realize 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 the angle stability, and is conducive to miniaturization.

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

[0035] 3) The third patch and inductor were further designed to isolate the AC signal generated when the metasurface was illuminated.

[0036] 4) Further, based on the design of a polarization conversion array to achieve rotational control of linear polarization, a polarization reflection array (i.e., a polarization reflection surface) is designed, which is 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. The electromagnetic wave undergoes multiple reflections, polarization conversions, and retransmissions between the resonant cavities, which can improve the working bandwidth of the polarization rotation surface, the transmittance of the electromagnetic wave, and the energy conversion rate; at the same time, the loss (including dielectric loss, reflection loss, diode power consumption, etc.) is reduced, and the performance is stable within a relative bandwidth of 10%, ensuring that the radar detection performance does not decrease; compared with the prior art that only realizes polarization conversion within a single frequency point or an extremely narrow frequency band, the present application has obvious bandwidth advantages and energy conversion advantages, can better match the radar system, and increase the degree of freedom for the radar target identification method.

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

[0038] 6) It is also necessary to explain that the present application only needs to be loaded in front of the antenna aperture of the radar system (specifically: it is loaded as a covering to the aperture of the single-polarization radar antenna, so that the original radar antenna and the polarizer together constitute a variable polarization antenna system). There is no need to modify the antenna system. It can not only be flexibly disassembled, but also enrich the single-polarization radar information detection dimension in a low-cost manner, thereby providing a new growth point for the improvement of radar target recognition capabilities. It has high reliability, takes into account both performance and cost, and is easy to implement engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a three-dimensional schematic diagram of a transmission type linear polarization rotating surface in one embodiment;

[0040] Figure 2 A top view of a polarization conversion unit in a transmission type linear polarization rotation surface according to an embodiment;

[0041] Figure 3 A schematic diagram of the principle of regulating the linear polarization inclination angle of a transmission-type linear polarization rotating surface by regulating the amplitude ratio of orthogonal polarization components in an embodiment;

[0042] Figure 4 A schematic diagram of the principle of improving the working bandwidth and energy transmission efficiency of a linearly polarized rotating surface by constructing a Fabry-Perot resonant cavity in a transmission-type linearly polarized rotating surface in an embodiment;

[0043] Figure 5 A graph showing the variation trend 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 is kept unchanged and the voltage of the diode on the first transmission layer is changed for a polarization conversion array of a transmission type linear polarization rotating surface in one embodiment;

[0044] Figure 6 A phase difference diagram between orthogonal polarized waves when a polarization conversion array of a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer;

[0045] Figure 7 A total transmission coefficient diagram of a polarization conversion array of a transmission type linear polarization rotating surface in one embodiment when the voltage of the diode on the second transmission layer is kept unchanged and the voltage of the diode on the first transmission layer is changed;

[0046] Figure 8 A curve diagram of linear polarization tilt angle variation when a polarization conversion array of a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer;

[0047] Fig. 9A diagram showing the transmission performance of a polarization reflection array of a transmission type linear polarization rotating surface for x-polarized waves and y-polarized waves in one embodiment;

[0048] Fig.10 is a graph showing the reflection performance of a polarization reflection array of a transmission-type linearly polarized rotating surface for u-polarized waves and v-polarized waves in one embodiment;

[0049] Fig.11 A graph showing a variation trend of the amplitude of the main polarization transmission coefficient with the resistance value (bias voltage) when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer;

[0050] Fig.12 A graph showing a variation trend of the cross-polarization transmission coefficient amplitude with the resistance value (bias voltage) when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer;

[0051] Fig.13 A phase difference diagram between orthogonal polarized waves when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer;

[0052] Fig.14 A total transmission coefficient diagram of a transmission type linear polarization rotation surface in one embodiment when the voltage of the diode on the second transmission layer is kept unchanged and the voltage of the diode on the first transmission layer is changed;

[0053] Fig.15 A curve diagram of a linear polarization tilt angle change when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer;

[0054] Fig.16 A diagram showing a variation trend of the amplitude of the main polarization transmission coefficient with the resistance value (bias voltage) when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the first transmission layer unchanged and changes the voltage of the diode on the second transmission layer;

[0055] Fig.17 A graph showing a variation trend of the cross-polarization transmission coefficient amplitude with the resistance value (bias voltage) when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the first transmission layer unchanged and changes the voltage of the diode on the second transmission layer;

[0056] Fig.18A phase difference diagram between orthogonal polarized waves when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of the diode on the first transmission layer unchanged and changes the voltage of the diode on the second transmission layer;

[0057] Fig.19 A total transmission coefficient diagram of a transmission type linear polarization rotation surface in one embodiment when the voltage of the diode on the first transmission layer is kept unchanged and the voltage of the diode on the second transmission layer is changed;

[0058] Fig. 20 A curve diagram of a linear polarization tilt angle change when a transmission type linear polarization rotating surface in one embodiment keeps the voltage of a diode on a first transmission layer unchanged and changes the voltage of a diode on a second transmission layer;

[0059] Fig.21 This is a distribution diagram of the polarization state of a y-polarized electromagnetic wave on a Poincaré sphere after being regulated by a transmission-type linear polarization rotating surface in an embodiment.

[0060] Reference numerals:

[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] Polarization reflection unit b; substrate layer 21; reflection layer 22;

[0063] Incident wave Ey; transmitted wave T; reflected wave F. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0065] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0066] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "multiple groups" means at least two groups, such as two groups, three groups, etc., unless otherwise clearly and specifically defined.

[0067] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0068] In addition, the technical solutions between the various embodiments of the present application can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0069] The present application provides a transmission type linear polarization 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: a plurality of polarization conversion units distributed in an array, and the polarization conversion unit includes: a dielectric layer, a first transmission layer and a second transmission layer.

[0071] The dielectric layer is a supporting component, providing a loading position for the first transmission layer and the second transmission layer; the dielectric layer is a square structure.

[0072] The first transmission layer is arranged on the top of the dielectric layer, and comprises: four first patches, four second patches, two third patches, two inductors and a diode.

[0073] The first patch is an arc-shaped strip structure, one end of which is arranged on a diagonal line of the dielectric layer, and the other end extends toward the corner end of the dielectric layer and is arranged on another diagonal line of the dielectric layer, and the first patch protrudes toward the edge of the dielectric layer; the four first patches are distributed at equal intervals 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; the first part and the second part are both strip 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 structure; the four second patches correspond one to one with the 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 is in a strip structure, and two third patches are respectively arranged on the two first patches connected to the diode and correspond to each other; one corresponding end of the two third patches is connected to the middle of the corresponding first patch, and the other corresponding end extends toward the edge of the dielectric layer to serve as a feed line.

[0076] The inductor corresponds to the third patch one by one, and the inductor is arranged on the corresponding third patch.

[0077] The diode is arranged between one corresponding end of two first patches facing each other (there is a gap between one corresponding end of the other two first patches facing each other), and the diode is arranged on the diagonal line of the dielectric layer; the two ends of the diode are connected to an external control circuit (the specific external control circuit is the prior art) to change the voltage of the diode. Specifically, the diode can be a PIN diode.

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

[0079] Preferably, the first part is a linear strip structure, and the first part is arranged on the diagonal of the dielectric layer; the second part is an arc-shaped strip structure axially symmetrically distributed about the first part, and the second part protrudes toward the corner end of the dielectric layer; the above arrangement can ensure the realization of polarization regulation in the xy direction and polarization regulation in the uv direction.

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

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

[0082] In this embodiment, orthogonal polarization refers to that the directions of the electric field vectors of a pair of electromagnetic waves are perpendicular to each other. Two pairs of orthogonal polarized waves are defined here. One pair refers to electromagnetic waves with polarization directions along the x and y directions, which are recorded as xy polarized waves, and the other pair refers to electromagnetic waves with polarization directions along the u and v directions, which are recorded as UV polarized waves. The angle between the xy direction and the UV direction is 45°, wherein 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 and the phase difference between the two is kept unchanged, the inclination of the synthetic polarization will change, which is manifested as a rotation of the linear polarization azimuth (the azimuth is defined as 2 times the inclination).

[0084] The voltage of the diode is changed so that the state of the diode gradually changes between full conduction and full cutoff to achieve rotational regulation of linear polarization. Specifically, the voltage of the diode on the first transmission layer is kept unchanged (i.e., both ends of the diode remain open), and the voltage of the diode on the second transmission layer is changed so that the state of the diode on the second transmission layer gradually changes between full conduction and full cutoff, so that the equivalent resistance gradually increases, and rotational regulation of linear polarization is achieved; or, the voltage of the diode on the second transmission layer is kept unchanged (i.e., both ends of the diode remain open), and the voltage of the diode on the first transmission layer is changed so that the state of the diode on the first transmission layer gradually changes between full conduction and full cutoff, so that the equivalent resistance gradually increases, and rotational regulation of linear polarization is achieved.

[0085] By changing the bias voltage at both ends of the PIN diode, the PIN diode can accurately represent different resistance values, thereby changing the equivalent circuit of the polarization conversion array, changing the equivalent impedance of the metasurface, and then changing the amplitude ratio of the horizontal polarization component to the vertical polarization component in a pair of orthogonal polarization waves, so that the amplitude ratio between the orthogonal polarization components changes after the electromagnetic wave passes through the polarization conversion array, and the intensity and direction of the electric field after vector synthesis change, and the polarization state of the synthesized electromagnetic wave will also change accordingly, realizing real-time and near-continuous control of the amplitude ratio of the orthogonal polarization wave; the linear polarization azimuth control effect at equal angle intervals can control the linear polarization wave to be a near-equatorial orbit (polarization state is distributed along the equator on the Poincaré sphere) linear polarization that covers half of the equatorial orbit; by selecting a suitable bias voltage, the inclination angle of the polarization state of the transmitted wave can be changed at equal intervals to achieve the effect of linear polarization rotation.

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

[0087]

[0088] Among them, t αβ It represents the transmission coefficient (transmission coefficient) of the incident β-polarized wave converted into α-polarized wave. Both α and β can be x or y. Here, t yy =t uu +t vv ,t xy =t uu -t vv, x 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 xy.

[0089] Usually, the transmitted wave is elliptically polarized, and the angle t (inclination) between the main 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 amplitude of the transmission coefficient of the main polarization and the cross polarization, the linear polarization tilt angle can be adjusted. In addition, the phase difference between the orthogonal polarization components should be as consistent as possible to ensure that the synthetic polarized wave is linearly polarized.

[0093] In another embodiment, it also includes: a polarization reflection array, the polarization reflection array is arranged above the polarization conversion array at intervals to form a Fabry-Perot resonant cavity, and the polarization components that originally cannot pass through the polarization conversion array are converted into orthogonal polarization waves after the polarization reflection array and reflected back to the polarization conversion array. At this time, according to the transmittance of the polarization conversion array to the orthogonal polarization waves, it can be known that the polarization waves after reflection can largely pass through the polarization conversion array. It should be noted that how to arrange the polarization reflection array and the polarization conversion array at intervals belongs to the prior art, for example: there is an air layer between the polarization reflection array and the polarization conversion array, and a non-metallic support column is provided in the air layer, or there is a foam layer between the polarization reflection array and the polarization conversion array.

[0094] Preferably, the polarized reflection array comprises: a plurality of polarized reflection units distributed in an array; the polarized reflection unit comprises: a substrate layer and a reflection layer arranged on the top of the substrate layer; the reflection layer comprises a plurality of reflection patches distributed in an array at intervals, the reflection patches are strip structures, so that the reflection layer forms a fence-like structure.

[0095] Further preferably, the polarization reflection unit corresponds to the polarization conversion unit one by one, the substrate layer is a square structure, and the four sides of the substrate layer are respectively parallel to the four sides of the dielectric layer, and the two ends of the reflection patch are respectively connected to a group of opposite sides on the top of the substrate layer to filter incident waves in different directions and only allow incident waves perpendicular to the length direction of the reflection patch to pass; for example, Figure 1 The polarization reflection unit in the system only has a partial reflection function for UV orthogonal polarization waves.

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

[0097] In this embodiment, if Figure 4 As shown in the figure, due to the reflection of electromagnetic waves and the loss of active devices, the loss is large and the transmittance is low. A Fabry-Perot resonant cavity is constructed. According to the Fabry-Perot (FP) resonance principle, the polarization reflective array has a partial reflection function for orthogonal polarized waves (specifically uv polarized waves here). The electromagnetic waves undergo 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 will be effectively improved. In addition, the above-mentioned process can effectively weaken the differences at different frequency points, thereby further improving the working bandwidth.

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

[0099] The above-mentioned transmission type linear polarization rotating surface is a polarization time-varying control metasurface, which has the following beneficial effects:

[0100] 1) A polarization conversion array (i.e., polarization control surface, also amplitude modulation surface) is designed. The first patch is a radiation arm of an arc-shaped strip structure and two first patches are connected by a diode. It has the ability to independently control the orthogonal polarization amplitude. It can control the transmitted wave in any direction by controlling the amplitude ratio of the orthogonal polarization components of the transmitted electromagnetic wave, and control the transmitted wave to a linear polarization with different inclination angles, thereby realizing the rotation control of the linear polarization inclination angle and the conversion between multiple polarization states. It has the ability to control the polarization state of the electromagnetic wave 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 dynamic polarization control. The electrically controlled variable polarization control has the advantages of fast control speed (control speed can reach hundreds of nanoseconds) and high control accuracy. It can realize 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 the angle stability, and is conducive to miniaturization.

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

[0102] 3) The third patch and inductor were further designed to isolate the AC signal generated when the metasurface was illuminated.

[0103] 4) Further, based on the design of a polarization conversion array to achieve rotational control of linear polarization, a polarization reflection array (i.e., a polarization reflection surface) is designed, which is 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. The electromagnetic wave undergoes multiple reflections, polarization conversions, and retransmissions between the resonant cavities, which can improve the working bandwidth of the polarization rotation surface, the transmittance of the electromagnetic wave, and the energy conversion rate; at the same time, the loss (including dielectric loss, reflection loss, diode power consumption, etc.) is reduced, and the performance is stable within a relative bandwidth of 10%, ensuring that the radar detection performance does not decrease; compared with the prior art that only realizes polarization conversion within a single frequency point or an extremely narrow frequency band, the present application has obvious bandwidth advantages and energy conversion advantages, can better match the radar system, and increase the degree of freedom for the radar target identification method.

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

[0105] 6) It is also necessary to explain that the present application only needs to be loaded in front of the antenna aperture of the radar system (specifically: it is loaded as a covering to the aperture of the single-polarization radar antenna, so that the original radar antenna and the polarizer together constitute a variable polarization antenna system). There is no need to modify the antenna system. It can not only be flexibly disassembled, but also enrich the single-polarization radar information detection dimension in a low-cost manner, thereby providing a new growth point for the improvement of radar target recognition capabilities. It has high reliability, takes into account both performance and cost, and is easy to implement engineering.

[0106] When the polarization conversion array keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer, the transmission performance of the polarization conversion array for orthogonal polarization electromagnetic waves (including transmission characteristics and polarization control capabilities) is analyzed. The results are as follows: Figures 5 to 8 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 brackets after T11 and T21 are the resistance values ​​of the PIN diode of the first transmission layer. Figure 5It can be seen that after the electromagnetic wave passes through the single-layer polarization conversion array structure, the amplitudes of the orthogonal polarization components are modulated separately, and show different change trends with the change of the diode resistance value. Among them, the amplitude of the main polarization component increases with the increase of the resistance value, and the amplitude of the cross-polarization component decreases with the increase of the resistance value.

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

[0109] like Figure 7 As shown, R U represents the resistance of the first transmission layer, and the legend shows 10 different resistance values ​​of the first transmission layer. Figure 7 It can be seen that the transmittance of electromagnetic waves passing through a single-layer polarization conversion array is relatively low, with the lowest being around 70%.

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

[0111] The transmission performance of the polarization reflective array for orthogonal polarization waves is analyzed. The results are as follows: Fig. 9 As Fig.10 As shown, where T yy With T xy They represent 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 They represent the reflection coefficients of the u-polarization component and the v-polarization component respectively when the incident wave is u-polarization. Fig. 9 and Fig.10 It can be seen that the polarization direction of the incident wave is in the y direction and is perpendicular to the metal grid, and the electromagnetic wave of the orthogonal polarization component is transmitted in the Fabry-Perot resonant cavity.

[0112] In order to further verify that the present application has good polarization changing function, simulation experiments were carried out using CST software and MATLAB software to examine the polarization control ability, bandwidth and energy transmission performance of the linearly polarized rotating surface composed of the polarization conversion array and the polarization reflection array.

[0113] When the transmission type linear polarization rotating surface keeps the voltage of the diode on the second transmission layer unchanged and changes the voltage of the diode on the first transmission layer, the transmission characteristics and polarization control ability of the linear polarization rotating surface to the transmitted wave 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 brackets after T11 and T21 are the resistance values ​​of the PIN diode of the first transmission layer, R U represents the resistance of the first transmission layer, and the legend shows 10 different resistance values ​​of the first transmission layer. Figures 11 to 15 It can be seen that after the electromagnetic wave irradiates the linear polarization rotation surface, as the bias voltage at both ends of the first transmission layer decreases, the corresponding PIN diode changes from a fully conductive state (corresponding to a resistance value of 1Ω) to a cut-off state (corresponding to a resistance value of 2kΩ). At this time, the transmittance of the main polarization electromagnetic wave component gradually increases, while the transmittance of the cross-polarization electromagnetic wave component gradually decreases. In the process of resistance value change, the phase difference between the two orthogonal polarization components is basically maintained at -180°, and the inclination angle of the transmitted wave varies in the range of [-45°, 0]. Compared with the control effect of the single-layer polarization conversion array structure, in the frequency range of 9.1GHz-10.1GHz, the inclination angle obtained after the linear polarization rotation surface control has a gentler change trend, showing a more stable broadband performance, and the transmittance is increased from 70% to 90%.

[0114] When the transmission type linear polarization rotating surface keeps the voltage of the diode on the first transmission layer unchanged and changes the voltage of the diode on the second transmission layer, the transmission characteristics and polarization control ability of the linear polarization rotating surface to the transmitted wave 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 brackets after T11 and T21 are the resistance values ​​of the PIN diode of the first transmission layer, R V represents the resistance of the second transmission layer, and the legend shows 10 different resistance values ​​of 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 linear polarization rotating surface is changed, the phase difference between the orthogonal polarization components remains near 0°, the control effect is manifested as the tilt angle changes in the range of [0, 45°], and the transmittance is increased to 87%.

[0115] like Fig.21 As shown, by adjusting the bias voltage across the diode on the first transmission layer and the bias voltage across the diode on the second transmission layer in turn, a linear polarization rotation effect with an inclination interval of 5° can be obtained, and the distribution trajectory of the corresponding polarization state on the Poincaré sphere is obtained. It can be seen that the linearly polarized incident wave can be adjusted to a near-orbit linear polarization covering half of the equatorial orbit.

[0116] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0117] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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 above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A transmission type linear polarization rotating surface, characterized in that: include: A polarization conversion array, the polarization conversion array comprising a plurality of polarization conversion units distributed in an array; The polarization conversion unit comprises: a square dielectric layer, a first transmission layer arranged on the top of the dielectric layer, and a second transmission layer arranged on the bottom of the dielectric layer; The first transmission layer comprises: four first patches in an arc-shaped strip structure and spaced apart; one end of the first patch is arranged on a diagonal line of the dielectric layer, and the other end extends toward the corner end of the dielectric layer and is arranged on another diagonal line of the dielectric layer; the four first patches are centrally symmetrically distributed about the center of the dielectric layer, so that the first transmission layer forms a windmill-shaped structure; one corresponding end of two opposite first patches is connected by a diode, and the diode is arranged on the diagonal line of the dielectric layer; The second transmission layer is connected to the first transmission layer, and the structures of the two are completely the same and orthogonal to each other; The voltage of the diode is changed so that the state of the diode gradually changes between full conduction and full cutoff, so as to realize the rotation regulation of linear polarization.

2. The transmission type linear polarization rotating surface according to claim 1, characterized in that: The first transmission layer further includes: four second patches corresponding to the four first patches one by one; The second patch includes: a first part and a second part; the first part and the second part are both 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 on the second patch is connected to the other end of the corresponding first patch.

3. The transmission type linear polarization rotating surface according to claim 2, characterized in that: The first transmission layer further includes: two third patches; The two third patches are respectively arranged on the two first patches connected to the diodes and correspond to each other one by one; one corresponding end of the third patch is connected to the middle of the corresponding first patch, and the other corresponding end extends toward the edge direction of the dielectric layer; The third patch is provided with an inductor.

4. The transmission type linear polarization rotating surface according to claim 3, characterized in that: The first portion is a linear strip structure, and the first portion is arranged on a diagonal line of the dielectric layer; The second portion is an arc-shaped strip structure, and the second portion protrudes toward the corner end of the dielectric layer.

5. The transmission type linear polarization 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. The transmission type linear polarization rotating surface according to claim 5, characterized in that: Changing the voltage of the diode so that the state of the diode gradually changes between fully conducting and fully cutting off, comprising: Keeping the voltage of the diode on the first transmission layer unchanged, and changing 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 turned on and fully turned off; Or, the voltage of the diode on the second transmission layer is kept unchanged, and the voltage of the diode on the first transmission layer is changed, so that the state of the diode on the first transmission layer gradually changes between fully turned on and fully turned off.

7. A transmission type linear polarization rotating surface according to any one of claims 1 to 6, characterized in that: Also includes: A polarization reflection array is arranged above the polarization conversion array at intervals to form a Fabry-Perot resonant cavity.

8. The transmission type linear polarization rotating surface according to claim 7, characterized in that: The polarization reflection array comprises: a plurality of polarization reflection units distributed in an array; The polarization reflection unit comprises: a substrate layer and a reflection layer arranged on the top of the substrate layer; The reflective layer includes a plurality of reflective patches distributed in an interval array, and the reflective patches are strip-shaped structures, so that the reflective layer forms a fence-shaped structure.

9. The transmission type linear polarization rotating surface according to claim 8, characterized in that: The polarization reflection unit corresponds to the polarization conversion unit one by one; The substrate layer is a square structure, and the four sides of the substrate layer are respectively parallel to the four sides of the dielectric layer; Two ends of the reflective patch are respectively connected to a group of opposite edges on the top of the substrate layer.

10. The transmission type linear polarization rotating surface according to claim 9, characterized in that: The reflective patch is a linear strip structure, any two reflective patches are arranged in parallel, and the distance between any two adjacent reflective patches is equal.

Images