A polarization reconfigurable converter based on active metasurface

Abstract

The present invention provides a polarization reconfigurable converter based on an active metasurface, wherein the polarization converter unit is composed of a single metasurface unit and a PIN diode, and each metasurface unit is composed of three layers of metal, three layers of dielectrics, and metallized vias connecting the top layer and the bottom layer. The polarization state of the reflected wave is controlled by controlling the peripheral voltage. The reflected wave can be a co-polarized wave or a cross-polarized wave. The converter is not only polarization-controllable for linear polarized waves, but also polarization-controllable for circular polarized waves. The operating frequency range of the structure covers the X-band, has a wide relative bandwidth, and has a high conversion efficiency within the entire bandwidth. The present invention is simple in design, has a small peripheral control voltage and a simple control circuit, is thin in thickness, has good versatility, can be designed in different operating frequency bands by adjusting the size structure, and is easy to promote and apply. It has potential application value in radar cross-section reduction and wireless communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of artificial electromagnetic materials, and in particular relates to a polarization reconfigurable converter based on an active metasurface. Background Art

[0002] Under information conditions, the polarization of electromagnetic waves is an important research content of electromagnetic wave space propagation. In communication technology, different polarizations have different propagation characteristics. Combined with the polarization characteristics of the transmitting and receiving antennas, the best transmission and reception of electromagnetic waves can be achieved. For example: Medium wave broadcasting uses vertical polarization propagation. Because of the characteristics of radio waves, if horizontally polarized radio waves propagate, polarized currents will be generated on the surface of the earth. The polarized currents are affected by the impedance of the earth, causing the electric field signal to attenuate, and the vertical polarization method is not easy to generate polarized currents; television, FM radio and shortwave broadcasting generally use horizontal polarization. Long-distance shortwave broadcasting is an ionospheric reflection propagation method. In the study of radar anti-interference, the interference of enemy horizontal polarized waves can be suppressed by the antenna operation of vertically polarized waves. Polarization is extremely important in electronic warfare, so the antenna needs to be reconfigurable for co-polarization and cross-polarization for both linear polarization and circular polarization. Usually, a pair of antennas has only one polarization, and a complex feeding network is required to achieve polarization control of the antenna. Therefore, a polarization converter is needed to achieve co-polarization and cross-polarization control for both linear polarization and circular polarization. Therefore, converters that meet the above polarization controllability have important new uses in modern radar, communications, electronic reconnaissance and jamming. Summary of the invention

[0003] The purpose of the present invention is to provide a polarization reconfigurable converter based on an active metasurface to solve the problem of achieving co-polarization and cross-polarization regulation for both linear polarized waves and circular polarized waves.

[0004] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0005] A polarization reconfigurable converter based on an active metasurface, comprising a plurality of polarization converter units;

[0006] The polarization converter unit includes a metasurface unit, each of which is added with a PIN diode;

[0007] The feeding of each column of metasurface units is controlled by the same signal; the control signals of all columns of metasurface units are connected to one end of the entire metasurface unit array for centralized control.

[0008] Furthermore, each metasurface unit also includes an upper dielectric substrate, a lower dielectric substrate, a solidified sheet, two metal feed through holes and three metal layers;

[0009] The three metal layers are respectively a metal patch at the top layer, a metal backplane in the middle, and a feeder layer at the bottom layer;

[0010] The metal patch of the top layer is arranged on the upper part of the upper dielectric substrate;

[0011] The curing sheet is arranged between the upper dielectric substrate and the lower dielectric substrate to adhere the upper dielectric substrate and the lower dielectric substrate together;

[0012] The intermediate metal back plate is arranged at the lower part of the upper dielectric substrate;

[0013] The metal feed through hole penetrates the upper dielectric substrate and the lower dielectric substrate and connects the metal patch on the top layer and the feed line layer on the bottom layer;

[0014] Each column of the DC feeder line of the bottom feeder line layer is finally connected to a signal control board at one end of the array, and the on-off of the PIN diode is controlled by controlling the peripheral voltage.

[0015] Furthermore, there are two sectors at the connection between the feed line and the metal feed through hole, which suppress the AC transmission to the DC feed line and reduce the influence of the feed line on the metal patch on the top layer.

[0016] Furthermore, the on and off states of the PIN diode are changed, and the reflection phase difference in the u direction is changed while maintaining the amplitude total reflection in the u direction; the size of the metal patch on the top layer is changed so that the reflection phase difference in the u direction is 180 degrees when the PIN diode is on and off, and the amplitude in the v direction is fully reflected, and the phase remains unchanged in the on and off states, thereby realizing the reconfiguration of the reflected wave into a co-polarized wave and a cross-polarized wave, wherein the u direction is the direction rotated 45° counterclockwise with respect to the x-axis, and the v direction is the direction rotated 45° clockwise with respect to the x-axis.

[0017] Furthermore, the PIN diode can be turned on when the voltage is 1V, and has a small peripheral control voltage.

[0018] Furthermore, the material of the upper dielectric substrate and the lower dielectric substrate is microwave composite material F4B.

[0019] The polarization reconfigurable converter based on active metasurface of the present invention has the following advantages:

[0020] 1. The principle of the present invention is simple. It only needs to change the peripheral control voltage to adjust the polarization state of the reflected wave in real time. The present invention uses multiple basic units to form an array and is controlled by the same signal, which can reduce the interference caused by different boundaries on the unit reflection coefficient and also reduce the complexity of the feed network design.

[0021] 2. The present invention is based on active metasurface technology and has the advantages of simple structure, low profile, reconfigurability, easy processing and relatively wide bandwidth compared with traditional polarization converters.

[0022] 3. The present invention is based on active metasurface technology. This structure can not only reconstruct the polarization of linearly polarized waves, but also reconstruct the polarization of circularly polarized waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1( a ) is a schematic diagram of a top metal patch of a single unit of the present invention;

[0024] FIG1( b ) is a schematic diagram of a single unit bottom DC feed layer of the present invention;

[0025] FIG. 1( c ) is an intermediate metal layer of the present invention;

[0026] FIG. 1( d ) is a side view of a single unit of the present invention;

[0027] Figure 2 The x, y, u, v coordinate system and the decomposition of the electric field u direction in both x and y directions are shown;

[0028] Figure 3 (a) is a schematic diagram of an equivalent circuit of the SMV1320-040LF PIN diode of the present invention when it is in an off state;

[0029] Figure 3 (b) is a schematic diagram of an equivalent circuit of the SMV1320-040LF PIN diode of the present invention when in a conducting state;

[0030] Figure 4 (a) is a schematic diagram showing a comparison of the reflection amplitude and phase simulation when the PIN tube of the present invention is disconnected and under the excitation of u and v polarized waves;

[0031] Figure 4 (b) is a schematic diagram showing a comparison of the reflection amplitude and phase simulation under the excitation of u and v polarized waves when the PIN tube of the present invention is turned on;

[0032] Figure 5 (a) is a comparison between simulation and actual measurement of the present invention in the disconnected state under x-polarized wave excitation;

[0033] Figure 5 (b) is a comparison between simulation and actual measurement of the present invention in the conduction state under x-polarized wave excitation;

[0034] Figure 5 (c) is a comparison between simulation and actual measurement of the present invention in the disconnected state under left-hand circularly polarized wave excitation;

[0035] Figure 5 (d) is a comparison between simulation and actual measurement of the present invention in the conduction state under left-hand circularly polarized wave excitation;

[0036] Figure 6 Schematic diagram of a polarization reconfigurable converter based on an active metasurface of the present invention.

[0037] Explanation of the markings in the figure: 1. PIN diode; 2. Metal feeding through hole; 3. Feeding line; 4. Upper dielectric substrate; 5. Curing sheet; 6. Lower dielectric substrate; 7. Middle metal backplane. DETAILED DESCRIPTION

[0038] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a polarization reconfigurable converter based on an active metasurface of the present invention in conjunction with the accompanying drawings.

[0039] like Figure 6 As shown, the present invention includes multiple polarization converter units, each polarization converter unit includes a metasurface unit, and each metasurface unit adds a PIN diode 1; the feeding of each column of metasurface units is controlled by the same signal; the control signals of all columns of metasurface units are connected to one end of the entire metasurface unit array for centralized control.

[0040] FIG1 shows the basic structure of a single metasurface unit, each of which further includes an upper dielectric substrate 4, a lower dielectric substrate 6, a layer of curing sheet 5, two metal feed through holes 2 and three layers of metal. The three layers of metal are respectively a metal patch at the top layer, a middle metal back plate 7 and a bottom feed line layer; the metal patch at the top layer is arranged on the upper part of the upper dielectric substrate 4; the curing sheet 5 is arranged between the upper dielectric substrate 4 and the lower dielectric substrate 6 to adhere the upper dielectric substrate 4 and the lower dielectric substrate 6 together; the middle metal back plate 7 is arranged at the lower part of the upper dielectric substrate 4; the metal feed through hole 2 penetrates the upper dielectric substrate 4 and the lower dielectric substrate 6 and connects the metal patch at the top layer and the feed line layer at the bottom layer; each column of DC feed lines 3 at the bottom feed line layer is finally connected to a signal control board at one end of the array, and the on-off of the PIN diode 1 is controlled by controlling the peripheral voltage.

[0041] As shown in Figure 1(a), the PIN diode 1 is attached to the surface of the metal patch on the top layer, as shown in Figure 2, where the orientation of the PIN diode 1 is along the u direction, where the u direction is 45° counterclockwise from the x-axis, and the v direction is 45° clockwise from the x-axis. In this way, the on and off of the PIN diode 1 will change the equivalent circuit of the u direction of a single unit, but will have no effect on the equivalent circuit in the v direction. By optimizing the size of the patch in the metasurface unit, the reflection amplitude is close to 1 when it is turned on and off, but the phase difference is around 180°. Since the PIN tube is perpendicular to the v direction, the on and off of the PIN tube has no effect on the equivalent circuit of the metasurface unit in the v direction. Figure 4They are the amplitude and phase responses of the PIN tube in different states under the excitation of u and v polarized waves respectively.

[0042] The metal patch on the top layer regulates the amplitude and phase of the electromagnetic wave, and the middle metal backplane 7 is used as an AC ground to prevent the transmission of electromagnetic waves. As shown in FIG1(c), two circular holes are opened on the middle metal backplane 7. As shown in FIG1(d), the diameters of the two circular holes are larger than the diameters of the metal feed through-holes 2 to prevent the ground from contacting the metal feed through-holes 2. As shown in FIG1(b), the metal feed through-holes 2 are used to bridge the bottom DC feeder line 3 with the metal patch on the top layer. The two DC feeder lines 3 on the bottom layer are used for feeding, and there are two sectors at the connection between the feeder line 3 and the metal feed through-hole 2. The function of the sectors is to suppress the transmission of AC to the DC feeder line and reduce the influence of the feeder line 3 on the metal patch on the top layer.

[0043] The material of the upper dielectric substrate (4) and the lower dielectric substrate (6) is a microwave composite material F4B, with a dielectric constant of 2.4. A thin curing sheet 5 is provided in the middle to bond the upper and lower dielectric layers together, with a thickness of 0.16 mm and a dielectric constant of 4.2. The size of each metasurface unit is 17*17*3 mm.

[0044] The control voltage of the present invention is 1V. Since the equivalent circuit of the PIN diode is different when it is turned on and off, as shown in the attached figure Figure 3 (a) and Figure 3 (b) When it is on, its equivalent circuit is an inductor connected in series with a resistor, and when it is off, it is equivalent to an inductor connected in series with a resistor.

[0045] from Figure 4 (a) and Figure 4 It can be seen from (b) that the reflection amplitudes are all above -1dB, indicating that the reflection efficiency is relatively high. By comparing the reflection phases, it can be seen that the reflection phases are different in different states, and the phase difference between the two states is about 180°. For v-polarized wave excitation, the reflection amplitude and phase remain almost unchanged in the on and off states. According to electromagnetic field theory, when PIN diode 1 is turned on, for x-polarized or y-polarized wave excitation, the reflected wave is still a co-polarized wave, and for a circularly polarized wave excitation, it is a cross-polarized wave reflection. When the PIN diode is disconnected, for x-polarized or y-polarized wave excitation, the reflected wave is still a cross-polarized wave, and for a circularly polarized wave excitation, it is a co-polarized wave reflection.

[0046] In order to verify the effectiveness of the designed structure, it was simulated in the electromagnetic simulation software CST and measured in a microwave darkroom. Figure 5 (a) Figure 5 (b) Figure 5 (c) and Figure 5(d) A comparison chart of simulation and actual measurement is given, R represents the inverse coefficient, wherein the first and second lower tables of R represent the incident wave polarization and the reflected wave polarization, respectively. It can be seen from the figure that the simulation and the actual measurement have a fairly high consistency, and the present invention covers the X-band from the 7.4-12GHz frequency range. The conversion efficiency is within -1dB. In addition, the linear polarization and circular polarization simulation curves are consistent, which makes it have a very huge application value in communications and radar scattering cross sections.

[0047] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A polarization reconfigurable converter based on an active metasurface, characterized in that: comprising a plurality of polarization converter units; The polarization converter unit comprises a metasurface unit, each of which is added with a PIN diode (1); The feeding of each column of metasurface units is controlled by the same signal; the control signals of all columns of metasurface units are connected to one end of the entire metasurface unit array for centralized control; Each metasurface unit also includes an upper dielectric substrate (4), a lower dielectric substrate (6), a solidification sheet (5), two metal feed through holes (2) and three metal layers; The three metal layers are respectively a top metal patch, a middle metal backplane (7), and a bottom feeder layer; The top metal patch is arranged on the upper part of the upper dielectric substrate (4); The two top metal patches are connected by a PIN diode (1); The curing sheet (5) is arranged between the upper dielectric substrate (4) and the lower dielectric substrate (6) to adhere the upper dielectric substrate (4) and the lower dielectric substrate (6) together; The intermediate metal back plate (7) is arranged at the lower part of the upper dielectric substrate (4); The metal feed through hole (2) penetrates the upper dielectric substrate (4) and the lower dielectric substrate (6) and connects the metal patch on the top layer and the feed line layer on the bottom layer; Each column of DC feeder wires (3) of the bottom feeder wire layer is ultimately connected to a signal control board at one end of the array, and controls the on and off of the PIN diode (1) by controlling the peripheral voltage; The on and off states of the PIN diode (1) are changed, and the reflection phase difference in the u direction between the on and off states is changed while maintaining the amplitude total reflection in the u direction; the size of the metal patch on the top layer is changed so that the reflection phase difference in the u direction is 180 degrees when the PIN diode (1) is on and off, and the amplitude total reflection in the v direction is simultaneously achieved, and the phase remains unchanged in the on and off states, thereby realizing the reconfiguration of the reflected wave into a co-polarized wave and a cross-polarized wave, wherein the u direction is a direction rotated 45 degrees counterclockwise with respect to the x-axis, and the v direction is a direction rotated 45 degrees clockwise with respect to the x-axis.

2. The polarization reconfigurable converter based on active metasurface according to claim 1, characterized in that: The connection between the feed line (3) and the metal feed through hole (2) has two fans, which suppress the transmission of alternating current to the direct current feed line and reduce the influence of the feed line (3) on the metal patch on the top layer.

3. The polarization reconfigurable converter based on active metasurface according to claim 1, characterized in that: The PIN diode (1) can be turned on when the voltage is 1V.

4. The polarization reconfigurable converter based on active metasurface according to claim 1, characterized in that: The material of the upper dielectric substrate (4) and the lower dielectric substrate (6) is microwave composite material F4B.

Images