Omnidirectional scanning leaky-wave antenna based on unidirectional edge mode

Abstract

The invention belongs to the technical field of antennas, and discloses an omnidirectional scanning leaky-wave antenna based on a one-way edge mode, which comprises a one-way waveguide formed by sequentially splicing a metal layer, an air layer and a photonic crystal, and the one-way waveguide has the one-way edge mode in an air light cone. Wherein the photonic crystal is formed by embedding periodically arranged square dielectric cylinders in a yttrium iron garnet background, a static magnetic field is applied to the photonic crystal in the z direction, and periodic hollow holes are formed in a metal layer of the one-way waveguide. According to the invention, the structure is simple, the photonic crystal forbidden band is low, and the full-space scanning capability from backward end emission, lateral radiation and forward end emission is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and in particular relates to an omnidirectional scanning leaky-wave antenna based on a unidirectional edge mode. Background Art

[0002] A unidirectional edge mode refers to an electromagnetic wave mode that can only propagate in one direction. It is immune to backscattering caused by defects (or bends) because there is no reverse propagation mode in the system.

[0003] Non-reciprocal devices are often essential elements in optical systems. Ideal non-reciprocal devices ensure perfect unidirectional signal transmission within the system. In addition to eliminating destructive feedback to the transmitting source, they can also greatly simplify the design of optical systems by suppressing multipath reflections between devices, and significantly improve the system's stability against manufacturing defects and environmental changes.

[0004] The frequency characteristics of a photonic crystal are closely related to its unit cell structure (such as aperture size and arrangement). For example, by changing the period length or porosity of a photonic crystal, its bandgap range and corresponding frequency can be adjusted.

[0005] Currently, leaky-wave antennas mainly include leaky-wave antennas based on artificial surface plasmons and traditional periodic microstrip leaky-wave antennas. However, photonic crystal leaky-wave antennas based on unidirectional edge modes are rarely mentioned. How to design them to have excellent leaky-wave performance is a challenging problem.

[0006] Chinese patent application publication number CN117410692A discloses "a side-beam scanning leaky-wave antenna based on a yttrium iron garnet cylindrical array," which can achieve side-beam scanning, but the beam scanning angle of its structure is very limited and the leakage method is not simple enough.

[0007] The photonic crystal leaky-wave antennas proposed in SCI papers such as "Broadside Radiation From Chern Photonic Topological Insulators" and "Tunable directional radiation and reception based on magneto-optical photonic crystal waveguides" are restricted by their photonic crystal structure. Their photonic bandgap is relatively high and cannot pass through the entire air light cone, resulting in a very limited scanning angle. Summary of the Invention

[0008] The purpose of the present invention is to provide an omnidirectional scanning leaky-wave antenna based on a unidirectional edge mode, which has a simple structure, a low photonic crystal bandgap, and the ability to scan the entire space from rear end-fire, through lateral radiation, and then to forward end-fire.

[0009] To achieve the above object, the technical solution adopted by the present invention is: An omnidirectional scanning leaky-wave antenna based on a unidirectional edge mode includes a unidirectional waveguide composed of a metal layer, an air layer, and a photonic crystal spliced in sequence. The unidirectional waveguide has a unidirectional edge mode within an air light cone. The photonic crystal is composed of periodically arranged square dielectric columns embedded in an yttrium iron garnet background, and a static magnetic field is applied to the photonic crystal along the z direction. The metal layer of the unidirectional waveguide is provided with periodic hollow holes.

[0010] Several optional methods are also provided below, but they are not intended to be additional limitations on the above-mentioned overall solution. They are merely further supplements or optimizations. Under the premise that there are no technical or logical contradictions, each optional method can be combined separately for the above-mentioned overall solution, or multiple optional methods can be combined.

[0011] Preferably, the periodic hollow holes are located in the middle of the metal layer.

[0012] Preferably, the lattice constant of the photonic crystal is a, and the side length of the square dielectric column is 0.25a-0.45a.

[0013] Preferably, the periodic hollow holes have a period constant of a, and the position of each hollow hole corresponds to the position of the square dielectric column.

[0014] Preferably, the thickness of the air layer is 0.85a-1.00a.

[0015] Preferably, the dispersion curve of the unidirectional waveguide in the unidirectional edge mode passes through the entire air light cone and is continuous at k=0, where k is a wave vector.

[0016] Preferably, the relative dielectric constant of the square dielectric column is relatively high, ranging from 170 to 200.

[0017] Preferably, the edge height of the photonic crystal is h, and h>0.

[0018] Preferably, the omnidirectional scanning leaky wave antenna has a full-space scanning mode from backward to forward as the operating frequency increases when the magnetic induction intensity of the static magnetic field is fixed; or has a full-space scanning mode from backward to forward as the magnetic induction intensity of the static magnetic field decreases at a fixed operating frequency.

[0019] The present invention provides an omnidirectional scanning leaky-wave antenna based on a unidirectional edge mode, which supports a unidirectional edge mode within an air light cone, and a dispersion curve that passes through the entire air light cone and is continuous at the wave vector k=0. The yttrium-iron-garnet (YIG) photonic crystal has a wide bandgap characteristic, and the bandgap position is significantly shifted downward. The leaky-wave antenna of the present invention is simple to operate and has the ability to scan the entire space from rear end-fire, through lateral radiation, and then to forward end-fire. It supports both omnidirectional scanning of a fixed magnetic frequency beam and omnidirectional scanning of a fixed frequency magnetic field beam, and can be applied to radar, beam control, space optical communication and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the two-dimensional structure of the omnidirectional scanning leaky-wave antenna based on the unidirectional edge mode of the present invention; Figure 2 Schematic diagram of the two-dimensional structure of the periodic unit structure of the omnidirectional scanning leaky wave antenna based on the unidirectional edge mode of the present invention; Figure 3 Schematic diagram of the two-dimensional structure of the photonic crystal unit cell of the present invention; Figure 4 (a) is the energy band diagram of the photonic crystal of the present invention when no external magnetic field is applied. Figure 4 (b) is the energy band diagram of the photonic crystal of the present invention when an external magnetic field is applied; Figure 5 (a) is a schematic diagram of a unidirectional waveguide structure. Figure 5 (b) is a schematic diagram of unidirectional waveguide transmission. Figure 5 (c) is the dispersion curve of the unidirectional waveguide edge mode; Figure 6 This is a graph showing the edge mode dispersion of the omnidirectional scanning leaky-wave antenna of the present invention; Figure 7 (a) is the far-field gain diagram of the omnidirectional scanning leaky-wave antenna of the present invention at different frequencies. Figure 7 (b) is a schematic diagram of the backward, side, and forward radiation of the omnidirectional scanning leaky-wave antenna of the present invention at different frequencies; Figure 8 (a) is the far-field gain diagram of the omnidirectional scanning leaky-wave antenna of the present invention under different magnetic fields, Figure 8 (b) is a schematic diagram of the backward, sideways and forward radiation of the omnidirectional scanning leaky wave antenna of the present invention under different magnetic fields. DETAILED DESCRIPTION

[0021] 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] Example 1: like Figure 1-Figure 2 As shown in FIG, the omnidirectional scanning leaky wave antenna based on the unidirectional edge mode of this embodiment includes a unidirectional waveguide composed of a metal layer, an air layer and a photonic crystal spliced in sequence. The photonic crystal layer of the unidirectional waveguide is composed of a periodic array of square dielectric columns in a YIG background, and an external magnetic field is applied in the z direction. The cross-sectional length of the unidirectional waveguide is set in the x direction, and the width is set in the y direction, so the z direction is the direction perpendicular to the xy plane. Figure 3 As shown, the photonic crystal lattice constant is a = 0.00672mm, the side length of the square dielectric column is 0.35a, and the operating frequency is 4.28GHz. When no external magnetic field is applied, the energy band diagram of the photonic crystal of this embodiment is as shown in FIG. Figure 4 As shown in (a), there is no obvious photon band gap within a certain frequency range. By applying an external magnetic field (static magnetic field, the magnetic field size is 1600G), the energy band diagram of the photonic crystal changes as follows Figure 4 As shown in (b), a wide photonic bandgap of 9.3% can be generated, and the bandgap position is significantly lower than that of traditional photonic crystals that support unidirectional edge modes. The thickness of the air layer is d = 0.9288a, and the outermost layer is truncated by a metal sheet.

[0024] In this embodiment, the photonic crystal YIG exhibits gyromagnetic properties under the action of an external magnetic field, and its relative magnetic permeability has the following form: Where, is the relative magnetic permeability, is the imaginary part, and are the first parameter and the second parameter respectively, and in this embodiment , , represents the characteristic angular frequency of the YIG material, represents the precession angular frequency, where is the gyromagnetic ratio, is the magnetic field strength of the external magnetic field, represents the angular frequency, Represents the loss of YIG material.

[0025] In order to achieve a significant effect, the relative dielectric constant of YIG is taken as , the relative dielectric constant of the square medium .

[0026] like Figure 5 As shown, in this embodiment, the photonic crystal boundary is cut so that the YIG edge height h=0.41275a. At this time, the structure of the unidirectional waveguide is as follows Figure 5 As shown in (a) in the figure, the unidirectional waveguide thus obtained supports a unidirectional edge mode in the air light cone, as shown in Figure 5 As shown in (b), the unidirectional edge mode is at the edge of the photonic crystal and the air, and is a leakage mode, such as Figure 5 As shown in (c), the leakage mode dispersion curve passes through the entire air light cone and is continuous at k=0. Therefore, it is very convenient to achieve mode leakage into free space by simply opening a hole in the metal sheet.

[0027] In order to achieve leakage, this embodiment periodically punches holes in the metal layer of the unidirectional waveguide, where the period constant is a and the aperture width is w=0.354a. Figure 6 As shown in the figure, the dispersion curve of the leaky-wave antenna of this embodiment passes through the entire air light cone in leakage mode and is continuous at k = 0. This embodiment simulates the metal layer as a perfect electric conductor, and the dispersion relation, far-field amplitude, and transmission simulation of the leaky-wave unit structure of this embodiment are obtained by numerical calculation using finite element simulation.

[0028] In this embodiment, by fixing the external magnetic field (the magnetic induction intensity of the external magnetic field is fixed at 1600G) and adjusting the working frequency, the leaky wave antenna can achieve full space scanning capability from rear end firing, lateral radiation, and then forward end firing. The leaky wave results are as follows: Figure 7 shown. Figure 7 Figure (a) shows the radiation angle and gain of the omnidirectional scanning leaky-wave antenna at different frequencies. It can be seen that the leaky-wave antenna in this embodiment achieves omnidirectional (180-degree) scanning in the upper half space from -90 degrees to 90 degrees with high gain. Figure 7 (b) shows the schematic diagram of the backward end-fire, side radiation, and forward end-fire of the leaky wave antenna at different frequencies (4.263 GHz, 4.275 GHz, and 4.285 GHz).

[0029] Example 2: Based on the leaky wave antenna structure of Example 1, this embodiment adjusts the magnetic induction intensity of the external magnetic field by fixing the operating frequency (the operating frequency is fixed at 4.28 GHz). The leaky wave antenna can achieve full-space scanning capability from rear end-fire, through lateral radiation, and then to forward end-fire. The leaky wave results are as follows: Figure 8 shown. Figure 8 Figure (a) shows the radiation angle and gain of the omnidirectional scanning leaky-wave antenna under different magnetic fields. It can be seen that the leaky-wave antenna in this embodiment achieves omnidirectional (180-degree) scanning in the upper half space from -90 degrees to 90 degrees with high gain. Figure 8 (b) shows the schematic diagram of the backward end-fire, side radiation and forward end-fire of the leaky wave antenna under different magnetic fields (1611G, 1600G and 1592G).

[0030] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0031] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An omnidirectional scanning leaky wave antenna based on a unidirectional edge mode, characterized in that: The omnidirectional scanning leaky-wave antenna based on a unidirectional edge mode includes a unidirectional waveguide composed of a metal layer, an air layer, and a photonic crystal spliced in sequence. The unidirectional waveguide has a unidirectional edge mode within the air light cone, wherein the photonic crystal is composed of periodically arranged square dielectric columns embedded in an yttrium iron garnet background, and a static magnetic field is applied to the photonic crystal along the z direction. The metal layer of the unidirectional waveguide is provided with periodic hollow holes.

2. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 1, characterized in that: The periodic hollow holes are located in the middle of the metal layer.

3. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 1, characterized in that: The lattice constant of the photonic crystal is a, and the side length of the square dielectric column is 0.25a-0.45a.

4. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 3, characterized in that: The periodic constant of the periodic hollow holes is a, and the position of each hollow hole corresponds to the position of the square dielectric column.

5. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 3, characterized in that: The thickness of the air layer is 0.85a-1.00a.

6. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 1, characterized in that: The dispersion curve of the unidirectional waveguide in the unidirectional edge mode passes through the entire air light cone and is continuous at k=0, where k is a wave vector.

7. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 1, characterized in that: The relative dielectric constant of the square dielectric column is 170-200.

8. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 1, characterized in that: The edge height of the photonic crystal is h, and h>0.

9. The omnidirectional scanning leaky wave antenna based on a unidirectional edge mode according to claim 1, characterized in that: The omnidirectional scanning leaky wave antenna has a full-space scanning mode from backward to forward as the operating frequency increases when the magnetic induction intensity of the static magnetic field is fixed; or has a full-space scanning mode from backward to forward as the magnetic induction intensity of the static magnetic field decreases at a fixed operating frequency.

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