A dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler

Abstract

The present invention discloses a dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler, which is composed of a surface wave guiding zone and a surface wave radiation zone. The surface wave guiding zone has four layers, with the first and third layers from top to bottom being F4B dielectric substrates, the second layer between the first and third layers being a thin layer of pure metal plate, and the fourth layer at the bottom being another thin layer of pure metal plate. The surface wave radiation zone follows the surface wave guiding zone along the x-direction and is composed of the same type of active adjustable metasurface units arranged in a simple repetitive manner in the x and y directions. The umbrella-shaped metal structure includes a left curved arm, a right curved arm, a middle straight rod, and bias leads on both sides. The technical effect of this invention is that it can realize the relatively independent design and regulation of the two radiation channels, and realize the dynamic control switching of the surface wave to two orthogonal circularly polarized radiation directions.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial electromagnetic metasurfaces, and in particular to a dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler. Background Art

[0002] Surface waves are a special type of electromagnetic wave mode that exists at the interface between two different dielectric materials, with the metal-dielectric interface being the most typical. The electromagnetic field distribution of surface waves is confined near the interface, and the wavelength propagating along the interface is smaller than the wavelength of free-space electromagnetic waves, while the corresponding wave vector is larger than the wave vector of free-space electromagnetic waves. Due to these special physical properties such as subwavelength, field localization, and strong dispersion, surface waves have great application prospects in new photonic integrated circuits, new absorbing materials, new surface wave antennas, and electromagnetic near-field sensors. Due to the different modes, surface waves cannot generally be directly generated by free-space wave irradiation. How to efficiently convert the two is an important fundamental issue in realizing surface wave applications. Traditional electromagnetic mode coupling technologies use devices such as prisms and gratings, but their efficiency is not very high and they are relatively large in size.

[0003] Artificial electromagnetic metasurfaces, also known as metasurfaces, are two-dimensional artificial structural functional materials that, through artificially designed periodic structures, can freely control the amplitude, phase, polarization, and waveform characteristics of electromagnetic waves. One type of phase gradient metasurface is a metasurface unit with different reflection phases arranged in a certain gradient direction, thereby changing the propagation direction of the reflected / refracted electromagnetic wave. Recent studies have shown that phase gradient metasurfaces can achieve efficient mutual coupling and conversion between surface waves and free-space waves. Many different forms of free-space wave-to-surface wave couplers have been developed, with their operating frequency bands continuously improved, mode types increased, and wavefront control capabilities increased. In addition, some couplers have also been developed that convert surface waves into free-space wave radiation.

[0004] Most existing couplers that convert surface waves into free-space wave far-field radiation operate in a single linear polarization mode and are designed to implement surface wave coupled radiation based on the classic passive phase gradient metasurface structure. However, once designed and manufactured, the radiation direction cannot be changed. These shortcomings limit their prospects for practical application.

[0005] To address the problems and shortcomings of these existing methods, the present invention discloses a dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiating coupler. Compared to other surface wave planar antennas, this invention features two orthogonal circularly polarized radiating channels. By incorporating active control devices, these two radiating channels can be independently designed and controlled, enabling dynamic switching of surface wave radiation to two orthogonal circularly polarized radiation directions. Summary of the Invention

[0006] The object of the present invention is to provide a dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler to solve the problems raised in the above background technology.

[0007] To achieve the above-mentioned purpose, the invention provides the following technical solutions: a dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler, which is composed of a surface wave guiding region and a surface wave radiation region;

[0008] The surface waveguide region has four layers. From top to bottom, the first and third layers are F4B dielectric substrates. The second layer between the first and third layers is a thin layer of pure metal plate. The fourth layer at the bottom is another thin layer of pure metal plate.

[0009] The starting end of the surface waveguide zone has a total of four side-by-side waveguide ports for feeding excitation;

[0010] The surface wave radiation zone follows the surface wave guiding zone along the x-direction and is formed by simply repeating the same active tunable metasurface units in the x- and y-directions.

[0011] The active adjustable metasurface unit is composed of an umbrella-shaped metal structure, an F4B dielectric substrate layer, and a metal backplane layer covered with all metal from top to bottom.

[0012] The umbrella-shaped metal structure includes a left curved arm, a right curved arm, a middle straight rod and bias leads on both sides;

[0013] The shapes of the left and right curved arms are a left arm arc and a right arm arc drawn with the center of the middle straight rod as the center of the circle;

[0014] The left arm arc and the right arm arc have the same radius, and a PIN diode is loaded in the middle;

[0015] The left curved arm and the right curved arm each have a coplanar DC bias lead, through which the positive electrode of the DC power supply can be loaded onto the positive electrode of the PIN diode;

[0016] The bottom end of the middle straight rod is connected to the bottom metal backplane through a metal via, and the negative electrode of the DC power supply can be loaded onto the negative electrode of the PIN diode through the via.

[0017] Preferably, the first layer and the third layer of the surface waveguide region are F4B dielectric substrates with thicknesses of 3 mm and =1 mm.

[0018] Preferably, the thickness of the F4B dielectric substrate layer of the active adjustable metasurface unit is =4 mm.

[0019] Preferably, the relative dielectric constant of the F4B dielectric substrate is 2.65, and the loss tangent value is 0.001.

[0020] Preferably, the working states of the PIN diode are divided into two types: "on" and "off", corresponding to loading or not loading the bias voltage respectively; under the incidence of left-hand circularly polarized wave or right-hand circularly polarized wave, the co-polarized reflection phase of the active adjustable metasurface unit corresponding to the "on" and "off" states of the left-arm or right-arm PIN diode differs by 180°; the left-arm or right-arm PIN diode can be independently controlled to control the reflection phase of the left-hand circularly polarized wave or the right-hand circularly polarized wave to change by 180° without causing the reflection phase of the right-hand circularly polarized wave or the left-hand circularly polarized wave to change.

[0021] Preferably, the active adjustable metasurface units with the same x-coordinate in the surface wave radiation area have their DC bias leads connected in series in a row along the y-direction, and the same bias voltage can be applied to the entire row at the same time, while a row of active adjustable metasurface units with different x-coordinates can apply different bias voltages, forming a phase modulation of the surface wave in the x-direction; the phase modulation method in the x-direction is selected in a periodically repeated manner, that is, several units are formed into a group, the bias states within the group are the same, and the bias states between the groups are different, and are arranged alternately in the "1" and "0" states; if a group has N metasurface units, then one modulation cycle requires 2N metasurface units.

[0022] Preferably, the surface wave radiation direction is changed by dynamically switching the bias voltage of each row in the surface wave radiation area, and the bias voltages of the left arm and the right arm are independently controlled, thereby independently controlling the radiation directions of the left-hand circular polarization and right-hand circular polarization channels.

[0023] Compared with the existing technology, the beneficial effects of the invention are: the dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler uses PIN diodes as switching components to control the metasurface structure of orthogonal circularly polarized independent dual channels. On the one hand, it can realize the independent design and regulation of the two circularly polarized radiations; on the other hand, it can manually and dynamically switch the working states of the two circularly polarized channels in real time to change the radiation direction, which can meet more application requirements of surface wave far-field directional radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the working mode of an embodiment of the dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler of the present invention, wherein: the virtual and real beams represent the changes in the directional radiation beam before and after the working state is switched;

[0025] Figure 2Schematic diagram of the surface waveguide region structure provided in an embodiment of the present invention, wherein: (a) is a schematic diagram of the waveguide port used for feeding; (b) is a three-dimensional view of a small structure of the waveguide region; (c) is a top-down schematic diagram of the surface waveguide region, with four protrusions at the far left end for accommodating the waveguide ports shown in (a); and (d) is a dispersion curve of the eigenstate surface wave in the waveguide region;

[0026] Figure 3 Schematic diagram of the active tunable metasurface unit structure and its circular polarization response performance provided by an embodiment of the present invention, wherein: (a) is a schematic diagram of the reflective metasurface unit structure, (b) is the simulation result of the reflection amplitude of the four coding states of the unit structure under circular polarization incidence, (c) is the simulation result of the co-polarization reflection phase of the four coding states under left-hand circularly polarized wave incidence, and (d) is the simulation result of the co-polarization reflection phase of the four coding states under right-hand circularly polarized wave incidence;

[0027] Figure 4 Schematic diagram of the equivalent circuit model of the SKYWORKS SMP1320 PIN diode in the "1" and "0" states used in the embodiments of the present invention;

[0028] Figure 5 Schematic diagrams of three working modes provided for embodiments of the present invention, wherein: (a) is the reflection phase distribution of two circularly polarized channels when the left-arm PIN diode applies "1" and "0" states alternately row by row along the x-direction, denoted as coupler working mode A; (d) is the far-field radiation simulation result at 10 GHz for coupler working mode A; (b) is the reflection phase distribution of two circularly polarized channels when the right-arm PIN diode applies "1" and "0" states alternately two rows along the x-direction, denoted as coupler working mode B; (e) is the far-field radiation simulation result at 10 GHz for coupler working mode B; (c) is the reflection phase distribution of two circularly polarized channels when the left-arm PIN diode applies "1" and "0" states alternately three rows along the x-direction, denoted as coupler working mode C; (d) is the far-field radiation simulation result at 10 GHz for coupler working mode C;

[0029] Figure 6 Schematic diagram of the radiation performance of samples of embodiments of the present invention and the results of their testing, where: (a) is a photo of the antenna sample, (b) is the far-field test environment and layout, (c) is the far-field radiation of 10 GHz operating mode A, (d) is the far-field radiation of 10 GHz operating mode B, and (e) is the far-field radiation of 10 GHz operating mode C. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Reference Figure 1 The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler of this embodiment includes: (1) a surface wave guiding region; and (2) a surface wave radiating region. The surface wave guiding region is used to transmit TM mode surface waves, and the surface wave radiating region applies phase modulation to the surface waves, converting them into electromagnetic wave radiation in two channels: left-hand circular polarization and right-hand circular polarization.

[0032] The surface waveguide zone has four layers. From top to bottom, the first and third layers are F4B dielectric substrates. The second layer between the first and third layers is a thin layer of pure metal plate. The fourth layer at the bottom is another thin layer of pure metal plate. On the left side of the surface waveguide zone, there are four side-by-side waveguide ports, which are fed and excited by the monopoles within them. The function of the surface waveguide zone is to first transition the radiation from the waveguide port into a surface wave mode with a certain wave vector value. The surface waveguide zone supports the propagation of eigenstate surface wave modes and can guide surface waves with specific wave vector characteristics to the subsequent surface wave radiation zone structure.

[0033] Reference Figure 2 (a) is a schematic diagram of the waveguide feeding port, which is a rectangular waveguide with a length, width, height and metal wall thickness of =19 mm, =21.8 mm, =14.8 mm, b=1.5 mm, built-in monopole antenna as excitation, antenna length =6 mm.

[0034] Reference Figure 2 (b) is a local stereoscopic diagram of the surface waveguide region, where the thicknesses of the first and third F4B dielectric substrates are =3 mm, =1 mm, the second layer is a thin layer of pure metal plate with a thickness of less than 0.02 mm, and the fourth layer is the bottom layer of pure metal plate with no limit on thickness.

[0035] Reference Figure 2 (c) is a top view of the surface waveguide region, where the length of the waveguide region in the x-direction is c=187.5 mm and the width in the y-direction is =150 mm, width of the four protruding parts on the left =21.8 mm, depth =19 m, used to place four waveguide ports for feeding.

[0036] Reference Figure 2 (d) is the dispersion curve of the upper eigenstate surface wave in the surface waveguide region. The wave vector value of the surface wave at 10 GHz is =1.08 , where The wave vector value of free space.

[0037] The surface wave radiation zone follows the surface wave guiding zone along the x direction and is formed by simply repeating the same active adjustable metasurface units in the x and y directions.

[0038] Reference Figure 3 (a) The active adjustable metasurface unit comprises a three-layer structure: from top to bottom, an umbrella-shaped metal structure, an F4B dielectric substrate layer, and a metal backplane layer covered with all metal.

[0039] The umbrella-shaped metal structure consists of three parts: a left curved arm, a right curved arm, and a central straight rod. The left and right curved arms are shaped like arcs centered on the center of the central straight rod, with the left and right arcs having the same radius. A PIN diode is loaded in the middle. Each arm has a coplanar DC bias lead, through which the positive terminal of the DC power supply can be connected to the positive terminal of the PIN diode. The bottom end of the central straight rod is connected to the underlying metal backplane via a metal via, through which the negative terminal of the DC power supply can be connected to the negative terminal of the PIN diode.

[0040] The working state of the PIN diode can be divided into two types: "on" and "off", corresponding to loading or not loading the bias voltage. Figure 4 In this example, a SKYWORKS SMP1320 PIN diode is used. The equivalent circuit model shows that the equivalent capacitance of the PIN diode changes significantly between the "on" and "off" states, enabling current conduction and cutoff to achieve switching.

[0041] The "on" and "off" states of a PIN diode can be represented by binary encoding as "1" and "0," respectively. Furthermore, the two PIN diodes in the left and right arms have four possible state combinations: "11," "10," "01," and "00," where the first binary digit represents the state of the left-arm PIN diode, and the second binary digit represents the state of the right-arm PIN diode. By optimizing the metal structure, it is possible to achieve a 180° phase difference between the co-polarized reflections corresponding to the "1" and "0" states of the left (right) PIN diode when incident with a left-handed circularly polarized wave (a right-handed circularly polarized wave) at a predetermined operating frequency. The corresponding optimized parameters in this example are p=10 mm, d=4 mm, r=3.6 mm, w=0.9 mm, v=0.2 mm, s=0.5 mm, t=1.85 mm, m=3.4 mm, n=0.4 mm, αL=αR=140°, β=65°, and γ=72°.

[0042] Reference Figure 3 (b) The co-polarization reflection amplitude coefficient of the active tunable metasurface unit can reach above 0.8 at 10 GHz in the four working states of "11", "10", "01" and "00".

[0043] Reference Figure 3 (c) The reflection phases for the left-arm "1" and "10" states are essentially the same, as are the reflection phases for the left-arm "0" and "01" states. The reflection phase difference between the left-arm "1" and left-arm "0" states is nearly 180°. In other words, the reflection phase of a co-polarized signal with left-hand circular polarization is essentially unaffected by the right arm.

[0044] Reference Figure 3 (d) The reflected phases for the right arm "1" ("11") and "10") are essentially the same, and the reflected phases for the right arm "0" ("01") and "00") are essentially the same. The reflected phase difference between the two states of right arm "1" and right arm "0" is nearly 180°. In other words, the co-polarized reflected phase for right-hand circularly polarized incident light is essentially unaffected by the left arm.

[0045] That is to say, by independently controlling the left-arm (right-arm) PIN diode to control the reflected phase of the left-hand circularly polarized wave (right-hand circularly polarized wave) to change by 180°, the reflected phase of the right-hand circularly polarized wave (left-hand circularly polarized wave) will basically not change.

[0046] The active adjustable metasurface units with the same x-coordinate in the surface wave radiation area have DC bias leads connected in series in a row along the y-direction. The same bias voltage can be applied to the entire row at the same time, while a row of active adjustable metasurface units with different x-coordinates can apply different bias voltages, thus forming a phase modulation of the surface wave in the x-direction. Generally, the phase modulation method in the x-direction is selected in a periodically repeated manner, that is, a number of units are formed into a group, the bias states within the group are the same, and the bias states between the groups are different, and they are arranged alternately in the two states of "1" and "0". If a group has N metasurface units, then one modulation cycle requires 2N metasurface units. According to the theory of electromagnetic wave diffraction, this modulation method can provide the surface wave with an additional wave vector that is opposite to the direction of the surface wave wave vector. , the calculation formula is (1)

[0047] Where p is the periodic interval of the metasurface unit. The direction of the directional radiation after coupling is calculated accordingly. , the calculation formula is (2)

[0048] By dynamically switching the bias voltage of each row, different additional wave vectors can be obtained. , realizing the change of surface wave radiation direction. And the bias voltage of the left and right arms can be controlled independently, thereby independently controlling the radiation direction of the left-hand circularly polarized and right-hand circularly polarized channels.

[0049] Reference Figure 5 , three working states of the dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler of this example are given. Figure 5 (a) shows the situation where N=1 metasurface units are grouped together and the left arm bias voltage is periodically modulated, which is recorded as working state A. Figure 5 (b) shows the situation where N=2 metasurface units are grouped together and the bias voltage of the right arm is periodically modulated, which is recorded as working state B. Figure 5 (c) shows the case where N = 3 metasurface units are grouped together and the left arm bias voltage is periodically modulated, which is recorded as working state C. According to formula (2), the theoretical radiation directions of the three working states at a frequency of 10 GHz are calculated to be -24.8°, 19.3°, and 35.5°, respectively. Figure 5 (d) shows the far-field radiation simulation results of the coupler in working state A, with the main lobe direction of radiation being -27.8°. Figure 5 (e) shows the far-field radiation simulation results of the coupler in working state B, with the radiation main lobe direction being 18.0°. Figure 5 (f) shows the far-field radiation simulation results of the coupler in operating state C, with the main lobe direction of radiation at 35.0°. The simulation results are basically consistent with the theoretical calculations.

[0050] In order to further verify the effectiveness of this design method, a set of dynamically adjustable surface wave orthogonal circular polarization dual-channel far-field directional radiation coupler samples that are exactly the same as those in the above simulations were manufactured using PCB technology. Figure 6 (a) The far-field radiation characteristics of the sample were tested in a microwave darkroom. The test environment is as follows: Figure 6 (b) See Figure 6 (c) Figure 6 (d) and Figure 6 (e) Test results at 10 GHz for operating states A, B, and C. The main lobe radiation angles are -20°, 21°, and 39°, respectively. The simulation results are largely consistent with theoretical calculations, demonstrating the effectiveness of this design.

[0051] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0052] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler, characterized by: It is composed of two parts: surface wave guiding area and surface wave radiation area; The surface waveguide region has four layers. From top to bottom, the first and third layers are F4B dielectric substrates. The second layer between the first and third layers is a thin layer of pure metal plate. The fourth layer at the bottom is another thin layer of pure metal plate. The starting end of the surface waveguide zone has a total of four side-by-side waveguide ports for feeding excitation; The surface wave radiation zone follows the surface wave guiding zone along the x-direction and is formed by simply repeating the same active tunable metasurface units in the x- and y-directions. The active adjustable metasurface unit is composed of an umbrella-shaped metal structure, an F4B dielectric substrate layer, and a metal backplane layer covered with all metal from top to bottom. The umbrella-shaped metal structure includes a left curved arm, a right curved arm, a middle straight rod and bias leads on both sides; The shapes of the left and right curved arms are a left arm arc and a right arm arc drawn with the center of the middle straight rod as the center of the circle; The left arm arc and the right arm arc have the same radius, and a PIN diode is loaded in the middle; The left curved arm and the right curved arm each have a coplanar DC bias lead, through which the positive electrode of the DC power supply can be loaded onto the positive electrode of the PIN diode; The bottom end of the middle straight rod is connected to the bottom metal backplane through a metal via, and the negative electrode of the DC power supply can be loaded onto the negative electrode of the PIN diode through the via.

2. The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler according to claim 1, characterized in that: The first and third layers of the surface waveguide region are F4B dielectric substrates with thicknesses of =3 mm, =1 mm.

3. The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler according to claim 1, characterized in that: The thickness of the F4B dielectric substrate layer of the active adjustable metasurface unit is =4 mm.

4. The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler according to claim 1, characterized in that: The relative dielectric constant of the F4B dielectric substrate is 2.65, and the loss tangent value is 0.

001.

5. The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler according to claim 1, characterized in that: The PIN diode has two working states: "on" and "off", corresponding to loading or not loading a bias voltage, respectively. When a left-hand circularly polarized wave or a right-hand circularly polarized wave is incident, the co-polarized reflection phase of the active adjustable metasurface unit corresponding to the "on" and "off" states of the left-arm or right-arm PIN diode differs by 180°. The left-arm or right-arm PIN diode can be independently controlled to control the reflection phase of the left-hand circularly polarized wave or the right-hand circularly polarized wave to change by 180° without causing a change in the reflection phase of the right-hand circularly polarized wave or the left-hand circularly polarized wave.

6. The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler according to claim 1, characterized in that: Actively adjustable metasurface units with the same x-coordinate in the surface wave radiation zone have their DC bias leads connected in series in a row along the y-direction. The same bias voltage can be applied to the entire row at the same time, while a row of actively adjustable metasurface units with different x-coordinates can be applied with different bias voltages, thereby forming phase modulation of the surface wave in the x-direction. The phase modulation method in the x-direction is selected in a periodically repeated manner, that is, several units are grouped into a group, the bias states within the group are the same, and the bias states between the groups are different, and the two states of "1" and "0" are arranged alternately. If a group has N metasurface units, then one modulation cycle requires 2N metasurface units.

7. The dynamically adjustable surface wave orthogonal circularly polarized dual-channel far-field directional radiation coupler according to claim 1, characterized in that: By dynamically switching the bias voltage of each row in the surface wave radiation area, the surface wave radiation direction is changed, and the bias voltages of the left arm and the right arm are independently controlled, thereby independently controlling the radiation directions of the left-hand circular polarization and right-hand circular polarization channels.

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