Reflection type polarization conversion antenna with adjustable stop band

Abstract

The invention discloses a reflection type polarization conversion antenna with an adjustable stop band, which works in an X wave band and is composed of a dielectric substrate, a metal resonance structure layer arranged on one side of the dielectric substrate and a metal reflection layer arranged on the other side of the dielectric substrate, and the metal resonance structure layer comprises two groups of mutually nested symmetrical split circular ring resonance units. Through the technical means of translation, parameter adjustment and the like, the two groups of resonance units generate symmetry difference, so that different resonance units generate mutually counteracted surface current responses at a specific frequency, and a stop band for polarization conversion suppression is formed in a continuous working frequency band; the position and suppression intensity of the stop band can be controlled by adjusting the structural parameters of each resonance unit. While broadband high-efficiency polarization conversion is realized, a tunable narrowband polarization conversion zero point is introduced, and the tunable narrowband polarization conversion zero point has the advantages of simple structure, high regulation degree of freedom and good incident angle stability, and is suitable for communication, radar and signal monitoring systems of millimeter wave and microwave frequency bands.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic metamaterials and antenna technology, specifically to a nonlocal polarization conversion metasurface structure for microwave and millimeter-wave bands and its design method, and particularly to a reflective polarization conversion metasurface with tunable polarization conversion stopband characteristics in a continuous operating frequency band. Background Technology

[0002] With the development of technologies such as wireless communication, radar detection, electronic countermeasures, and signal monitoring, higher demands are being placed on the modulation of electromagnetic wave polarization states. Polarization converters, as crucial devices for achieving electromagnetic wave polarization state modulation, have been widely applied in antenna systems, stealth technology, and information processing systems.

[0003] Traditional polarization converters are typically implemented using anisotropic or multilayer dielectric structures, which limit their operating bandwidth and make it difficult to introduce suppression of specific frequencies while achieving wideband polarization conversion. To meet the application requirements in complex electromagnetic environments, researchers have proposed polarization conversion metasurface structures with stopband characteristics. These structures maintain wideband polarization conversion capabilities while suppressing polarization conversion within a predetermined narrow frequency band, thereby achieving spectral selectivity.

[0004] In recent years, nonlocal metasurfaces based on high-quality factor resonant modes in periodic structures have gradually attracted attention. Related research shows that by rationally designing periodic structures, narrowband resonant characteristics can be introduced into the continuous spectrum, and used for applications such as beamforming, filtering, and polarization control. However, most existing technologies use a single resonant unit or introduce symmetry breaking within the unit to achieve stopband functionality, resulting in limited degrees of freedom in adjustment. The stopband position and performance are difficult to adjust flexibly, and there are shortcomings in achieving multi-frequency or extended stopbands.

[0005] Therefore, there is an urgent need for a nonlocal polarization conversion metasurface structure and its design method that is simple in structure, has a high degree of controllability, and can introduce an adjustable polarization conversion stopband within the continuous operating frequency band, so as to meet the needs of practical engineering applications. Summary of the Invention

[0006] To address the aforementioned shortcomings in existing technologies, the present invention aims to provide a nonlocal polarization conversion metasurface structure with an adjustable stopband and its design method. By introducing structural parameter differences at the supercell level, it achieves a balance between broadband polarization conversion and narrowband polarization conversion suppression. A further objective of this invention is to achieve flexible adjustment of the center frequency and suppression intensity of the polarization conversion stopband by controlling the structural parameters of different resonant units, thereby improving the design freedom and engineering applicability of the metasurface.

[0007] To achieve the above-mentioned objectives, the specific technical solution adopted by this invention is as follows:

[0008] A nonlocal polarization conversion metasurface structure with tunable stopband, characterized in that:

[0009] It includes a dielectric substrate, a metal resonant structure layer disposed on one side of the dielectric substrate, and a metal reflective layer disposed on the other side of the dielectric substrate, wherein the dielectric substrate, the metal resonant structure layer and the metal reflective layer are stacked along the same rectangular coordinate system.

[0010] The dielectric substrate is a flat plate structure, and its material is F4Bm350 high-frequency dielectric material; the metal resonant structure layer and the metal reflective layer are both made of metal materials.

[0011] The metal resonant structure layer is composed of multiple periodically arranged supercells, each supercell including at least a first resonant unit and a second resonant unit, the first resonant unit and the second resonant unit differing in geometric structural parameters.

[0012] Under electromagnetic wave incident conditions, the first resonant unit and the second resonant unit generate surface current responses with equivalent amplitude and opposite direction at a predetermined frequency, thereby suppressing the polarization conversion at that frequency and forming at least one polarization conversion stopband within the continuous operating frequency band; the center frequency and suppression intensity of the polarization conversion stopband can be controlled by adjusting the structural parameters of the first resonant unit and the second resonant unit.

[0013] The resonant unit is preferably a ring-shaped metal resonant structure, and the radius parameters of the first resonant unit and the second resonant unit are different; multiple resonant units are arranged in a periodic nested manner in the plane to form a nonlocal metasurface structure.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. By introducing resonant units with different structural parameters at the supercell level, narrowband polarization conversion suppression function is achieved while maintaining wideband polarization conversion performance;

[0016] 2. The position and suppression intensity of the polarization conversion stopband can be adjusted by structural parameters, which is intuitive and offers high design freedom;

[0017] 3. By adopting a nonlocal periodic structure, the metasurface maintains stable polarization conversion performance under oblique incidence conditions within a certain range;

[0018] 4. It has a simple structure, is easy to process and manufacture, and is suitable for engineering applications in the microwave and millimeter-wave frequency bands. It has good practical value and promotion prospects. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the structure of a single resonant unit in one embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the planar structure of a supercell composed of multiple resonant units;

[0021] Figure 3 This is a schematic diagram of the periodic array structure of the nonlocal polarization conversion metasurface of the present invention;

[0022] Figure 4 This is a schematic diagram of the polarization conversion response of the metasurface of the present invention at different frequencies. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent transformations or substitutions made by those skilled in the art without departing from the technical solution of the present invention should fall within the protection scope of the present invention.

[0024] Example 1: Single-band nonlocal polarization conversion metasurface structure

[0025] (I) Structural Composition

[0026] The dielectric substrate is a rectangular flat plate structure, and its material is F4Bm350 high-frequency dielectric material. The preferred thickness of the dielectric substrate is 2 mm, the dielectric constant is about 3.5, and the loss tangent is less than 0.002.

[0027] The metal reflective layer is disposed on the bottom surface of the dielectric substrate and is used to reflect incident electromagnetic waves. The preferred material for the reflective layer is a copper metal layer.

[0028] The metal resonant structure layer is disposed on the top surface of the dielectric substrate, and its material is preferably a copper metal layer.

[0029] The metal resonant structure layer is composed of multiple periodically arranged supercells, which are periodically arranged in two orthogonal directions in the plane to form a nonlocal metasurface structure.

[0030] (ii) Supercell structure

[0031] Each supercell includes at least a first resonant unit and a second resonant unit. Both the first and second resonant units are toroidal metal resonant structures, but their geometric dimensions are different.

[0032] In this embodiment, the equivalent radius of the first resonant unit is denoted as r1, and the equivalent radius of the second resonant unit is denoted as r2, and r1 ≠ r2.

[0033] Preferably, the first resonant unit and the second resonant unit are nested within the same supercell, so that different resonant units form nonlocal resonant modes under electromagnetic coupling.

[0034] The equivalent period of the supercell is P, where P can be selected according to the operating frequency band. In millimeter-wave applications, P is preferably located in the range of 8 mm to 15 mm.

[0035] (III) Operating frequency band and polarization conversion characteristics

[0036] When a linearly polarized electromagnetic wave is incident perpendicularly onto the metasurface, the metal resonant structure layer can achieve a highly efficient reflective polarization conversion from linear polarization to orthogonal linear polarization within the non-stopband frequency range.

[0037] By adjusting the size difference between the first resonant unit and the second resonant unit, they can generate surface current distributions with similar amplitudes and opposite directions at a specific frequency, thereby causing the overall surface currents to cancel each other out, suppressing the polarization transition at that frequency, and forming a polarization transition stopband.

[0038] In this embodiment, the metasurface operates in the frequency band of 11 GHz to 18 GHz, forming a polarization conversion stopband around 13.5 GHz, where the polarization conversion rate is significantly reduced and the co-polarization reflection component is enhanced.

[0039] Example 2: Single-band nonlocal polarization conversion metasurface structure

[0040] Based on Embodiment 1, the polarization conversion stopband characteristics can be tuned by changing the geometric dimensions of the first resonant unit and the second resonant unit.

[0041] Specifically:

[0042] When the difference between |r1 − r2| is increased, the suppression strength of the polarization switching stopband is enhanced;

[0043] As the difference between |r1 − r2| decreases, the polarization switching stopband gradually weakens until it disappears;

[0044] By synchronously adjusting the absolute dimensions of r1 and r2, the center frequency of the stopband can be shifted as a whole.

[0045] This allows for flexible control of the center frequency and suppression depth of the polarization conversion stopband within a continuous operating frequency band.

[0046] Example 3: Case Study on Incident Angle Stability

[0047] Based on the above embodiments, the working performance of the nonlocal polarization conversion metasurface under different incident angle conditions was verified.

[0048] The results show that the metasurface can maintain stable polarization conversion performance and polarization conversion stopband characteristics under normal incidence and oblique incidence conditions within a certain range, indicating that the structure has good incident angle stability and is suitable for power supply and application requirements in practical engineering environments.

[0049] As can be seen from the above embodiments, the nonlocal polarization conversion metasurface structure proposed in this invention is as follows:

[0050] 1. Achieve high-efficiency polarization conversion over a wide bandwidth;

[0051] 2. Introduce a tunable polarization switching stopband in the continuous spectrum;

[0052] 3. Achieve spectral selectivity control by adjusting structural parameters;

[0053] 4. It has the advantages of simple structure, easy processing, and strong engineering applicability.

Claims

1. A nonlocal polarization conversion metasurface structure with tunable stopband, characterized in that, include: A top metal resonant structure layer (1), a dielectric substrate (2), and a bottom metal reflective layer (3) are all disposed in the same rectangular coordinate system; wherein: The metal resonant structure layer (1) is a periodically arranged plurality of symmetrically split rings, with each pair of rings forming a square supercell. The two sets of units are defined as the first resonant unit (11) and the second resonant unit (12), respectively. The first resonant unit (11) is located at the center of the cell, and the second resonant unit (12) is divided into four equal parts and located at the four corners of the cell, forming a complete ring with the adjacent cells of the same structure. The first resonant unit (11) and the second resonant unit (12) are given different radii to achieve controllable symmetry breaking. The dielectric substrate (2) is square and has the same side length as the metal resonant structure layer (1). The bottom metal reflective layer (3) is square and has the same side length as the metal resonant structure layer (1) and the dielectric substrate (2). The metal resonant structure layer (1) has a test fixing hole (13) on its periphery; the dielectric substrate (2) has a test fixing hole (21) on its periphery; and the bottom metal reflective layer (3) has a test fixing hole (31) on its periphery.

2. The reflective polarization conversion antenna with adjustable stopband according to claim 1, characterized in that, The overall structure of the antenna exhibits a high degree of periodic symmetry, with the central region being a reflective operating area and the outermost metal resonator structure at the edge serving to provide a periodic structure for the internal structure.

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