Terahertz circular polarization orbital angular momentum array antenna

Abstract

The invention provides a terahertz circularly polarized orbital angular momentum array antenna which is composed of six units which are rotationally and symmetrically distributed, the rotation angle is 60 degrees, a graphene patch is arranged on the upper surface of an upper dielectric substrate, and the working frequency of the antenna can be adjusted; the upper dielectric substrate is circular; the metal square parasitic patch layer is located on the lower surface of the upper dielectric substrate, and the working bandwidth and the circular polarization axial ratio bandwidth are expanded. The metal chamfer patch is arranged on the upper surface of the lower dielectric substrate; the metal corner cut patch and the metal rectangular parasitic patch are arranged on the upper surface of the lower dielectric substrate; the supporting columns are located between the upper dielectric substrate and the lower dielectric substrate and are made of polyimide. The metal chamfer patch and the metal rectangular parasitic patch generate circularly polarized electromagnetic waves. The antenna uses a coaxial feed port, stable integer order orbital angular momentum vortex waves with modal values l = 0, + 1 and + 2 and stable fractional order orbital angular momentum vortex waves with modal values l = + 0.5 and + 1.5 can be generated only by adjusting a feed phase difference, and the maximum gain is 15.1 dBi when the modal value l = + 1.

Description

Technical Field

[0001] The present invention relates to the field of orbital angular momentum antennas, in particular to a terahertz circularly polarized orbital angular momentum array antenna. Background Art

[0002] Terahertz (THz) is generally defined as the electromagnetic wave frequency range of 0.1 to 10 THz. This special frequency band in the electromagnetic spectrum lies between microwaves and infrared light, combining the penetrating properties of microwaves with the light wave characteristics of infrared light. With the rapid development of wireless communication technology, the demand for higher data transmission rates and greater network capacity continues to increase. In recent years, the THz frequency band has attracted the attention of numerous researchers due to its excellent properties and enormous potential.

[0003] Electromagnetic waves carry angular momentum and linear momentum during propagation. Angular momentum includes spin angular momentum and orbital angular momentum. Spin angular momentum can be considered the polarization of the electromagnetic wave, while orbital angular momentum is related to the distribution of the electromagnetic wave's spatial phase. Its modal value, l, can theoretically take on any integer value. Furthermore, each mode is orthogonal to the others, and each transmission channel is independent. This provides a new approach to electromagnetic wave reuse that can effectively alleviate the scarcity of spectrum resources.

[0004] The polarization characteristics of an antenna are defined by the spatial orientation of the electric field strength vector of the electromagnetic wave radiated by the antenna in the direction of maximum radiation. Based on the movement of the electric field strength vector, it is classified as linear polarization, circular polarization, and elliptical polarization. Linear polarization is further divided into horizontal polarization and vertical polarization; circular polarization is divided into left-hand circular polarization and right-hand circular polarization. The trajectory of the end of the circularly polarized electric field vector is projected as a circle on a plane perpendicular to the propagation direction. The vector rotates at a constant rate. Due to its strong ability to resist multipath interference, circular polarization has shown significant advantages in wireless communications, navigation, and remote sensing.

[0005] Graphene, a two-dimensional nanomaterial composed of a single-layer hexagonal honeycomb lattice of carbon atoms, boasts ultrahigh electrical conductivity, approaching that of a superconductor. It also exhibits excellent thermal conductivity and chemical stability, making it adaptable to extreme environments. Its excellent tensile strength and low surface density make it suitable for the manufacture of flexible components. By applying an external voltage or varying the doping, the chemical potential of graphene can be adjusted, altering its surface conductivity without changing the antenna structure, thus enabling reconfigurable antenna frequency. Therefore, graphene, with its unique properties, has numerous future applications. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention proposes a terahertz circularly polarized orbital angular momentum array antenna that achieves adjustable operating frequency by adjusting the chemical potential of graphene. Modal value reconfiguration is achieved by simply adjusting the feed phase difference, generating stable integer-order orbital angular momentum vortex waves with modal values l = 0, +1, and +2, and fractional-order orbital angular momentum vortex waves with modal values l = +0.5 and +1.5. The maximum gain is 15.1 dBi at the modal value l = +1. The present invention provides the following technical solutions:

[0007] A terahertz circularly polarized orbital angular momentum array antenna is disclosed. The antenna is a left-hand circularly polarized antenna composed of 6 antenna units. The antenna units are rotationally symmetrically distributed and evenly arranged at a 60° rotation angle to form a ring array antenna. The array antenna includes a graphene patch, an upper dielectric substrate, a metal square parasitic patch, a support column, a metal cut-corner patch, a metal rectangular parasitic patch, a lower dielectric substrate and a metal ground layer. The graphene patch is located on the upper surface of the upper dielectric substrate, the metal square parasitic patch is located on the lower surface of the upper dielectric substrate, the support column is located between the upper and lower dielectric substrates, the metal corner-cut patch and the metal rectangular parasitic patch are on the upper surface of the lower dielectric substrate, the metal ground layer is located on the lower surface of the lower dielectric substrate, and a feeding port is provided at the center of the bottom edge of the metal corner-cut patch. The antenna adopts a coaxial feeding mode, and when the six feeding ports are continuously fed with phase differences of 0°, 30°, 60°, 90°, and 120°, integer-order orbital angular momentum vortex waves with modal values l=0, +1, and +2 and fractional-order orbital angular momentum vortex waves with l=+0.5 and +1.5 are generated.

[0008] Preferably, the upper dielectric substrate and the lower dielectric substrate are both circular, made of SiO2, with a radius of 90 μm; the thickness of the upper dielectric substrate is 0.5 μm, the thickness of the lower dielectric substrate is 1.5 μm, the gap between the upper dielectric substrate and the lower dielectric substrate is 2.5 μm; the relative dielectric constant of the upper dielectric substrate and the lower dielectric substrate is 3.75.

[0009] Preferably, the graphene patch has a side length of 7.65 μm and is square in shape; the metal square parasitic patch has a side length of 12.15 μm; the graphene patch is arranged in a circular array with the center of the circular dielectric substrate as the center, the center of the graphene patch is located 60 μm away from the center of the dielectric substrate, and the metal square parasitic patch is arranged in a circular array with the graphene patch as the center.

[0010] Preferably, the support pillars are cylinders, there are 6 of them, made of polyimide, with a relative dielectric constant of 3.5, a bottom radius of 0.5 μm, and a height of 2.5 μm. The center of the support pillar is 85 μm away from the center of the dielectric substrate.

[0011] Preferably, there are 6 metal corner-cut patches, and the corner-cut patches are distributed in rotational symmetry with a rotation angle of 60°.

[0012] Preferably, the distance between the metal corner cut patch and the metal rectangular parasitic patch is 0.2 μm, the two sides of the metal rectangular parasitic patch are 4.85 μm and 7 μm respectively, and the metal corner cut patch is a rectangular diagonal cut with a side length of 11.8 μm and a cut corner length of 4.8 μm.

[0013] Preferably, the feeding port has a diameter of 2.5 μm, and its center is 56.175 μm away from the center of the dielectric substrate.

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

[0015] By applying voltage and changing doping, the chemical potential of graphene can be adjusted, changing the surface conductivity of graphene without changing the antenna structure, thus achieving adjustable operating frequency. The design achieves a wider operating bandwidth and circularly polarized axial ratio bandwidth, while also achieving higher gain characteristics while generating a greater number of orbital angular momentum vortex waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0017] Figure 1 is a top view of the array structure of the antenna of the present invention;

[0018] Figure 2 is a side view of the array structure of the antenna of the present invention;

[0019] Figure 3 1. It is a unit structure diagram and a cut-corner patch diagram of the antenna of the present invention;

[0020] Figure 4 is the antenna S under different chemical potentials of graphene materials 11 curve chart;

[0021] Figure 5 is the antenna axial ratio curve under different chemical potentials of graphene materials;

[0022] Figure 6 is a gain curve diagram of the antenna modal value l=+1 of the present invention;

[0023] Figure 7 This is a vortex phase diagram of different modal values at 5.7 THz of the present invention. DETAILED DESCRIPTION

[0024] 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.

[0025] In order to make the above-mentioned objects, features and effects of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, an embodiment of the present invention is a terahertz circularly polarized orbital angular momentum array antenna, which is a left-handed circularly polarized antenna composed of 6 antenna units. The antenna units are rotationally symmetrically distributed and are evenly arranged at a rotation angle of 60° and 60 μm from the center to form a circular array antenna.

[0027] like Figure 2 As shown, the array antenna includes a graphene patch, an upper dielectric substrate, a metal square parasitic patch, a support post, a metal corner-cut patch, a metal rectangular parasitic patch, a lower dielectric substrate, and a metal ground layer. The graphene patch is located on the upper surface of the upper dielectric substrate, the metal square parasitic patch is located on the lower surface of the upper dielectric substrate, the support post is located between the upper and lower dielectric substrates, the metal corner-cut patch and the metal rectangular parasitic patch are located on the upper surface of the lower dielectric substrate, and the metal ground layer is located on the lower surface of the lower dielectric substrate. A feed port is located at the center of the bottom edge of the metal corner-cut patch.

[0028] The upper dielectric substrate and the lower dielectric substrate are both circular, made of SiO2, with a radius of 90 μm; the thickness of the upper dielectric substrate is 0.5 μm, the thickness of the lower dielectric substrate is 1.5 μm, and the gap between the upper and lower dielectric substrates is 2.5 μm; the relative dielectric constant of the upper and lower dielectric substrates is 3.75.

[0029] The graphene patch has a side length of 7.65 μm and a square shape. The graphene temperature is 300 K, the chemical potential is 1 eV, and the relaxation time is 1 ps. The metal square parasitic patch has a side length of 12.15 μm. The graphene patch is arranged in a circular array with the center of the circular dielectric substrate as the center. The center of the graphene patch is located 60 μm away from the center of the dielectric substrate. The metal square parasitic patches are arranged in a circular array with the graphene patch as the center.

[0030] The support pillars are cylindrical, there are 6 of them, made of polyimide, with a relative dielectric constant of 3.5, a bottom circle radius of 0.5 μm, and a height of 2.5 μm. The center of the support pillar is 85 μm away from the center of the dielectric substrate.

[0031] There are 6 metal cut-angle patches, which are distributed in rotational symmetry with a rotation angle of 60°; Figure 3 As shown, the distance between the metal corner cut patch and the metal rectangular parasitic patch is 0.2 μm, the two sides of the metal rectangular parasitic patch are 4.85 μm and 7 μm respectively, the metal corner cut patch is a rectangular diagonal cut corner with a side length of 11.8 μm and a cut corner length of 4.8 μm, the feeding port has a diameter of 2.5 μm, and the center is 56.175 μm away from the center of the dielectric substrate.

[0032] By applying voltage, changing doping and other means, the chemical potential of graphene can be adjusted, the surface conductivity of graphene can be changed, and the antenna structure can be kept unchanged, thus achieving the adjustable function of the antenna's operating frequency. By adjusting the chemical potential of graphene between 0.6 and 2.0 eV, the antenna can finally achieve frequency adjustment within the range of 5.3 to 5.7 THz, as shown in the following figure. Figure 4 and Figure 5 The simulation results of Figure 4 is the antenna S under different chemical potentials of graphene materials 11 Curve graph, where the chemical potential range of the left graph is 0.6~1.4eV; the chemical potential range of the right graph is 1.4~2.0eV; Figure 5 The following graphs show the antenna axial ratio under different chemical potentials of graphene materials. The left graph shows a chemical potential range of 0.6–1.4 eV, while the right graph shows a chemical potential range of 1.4–2.0 eV. It can be seen that as the chemical potential increases, the antenna's central operating frequency shifts toward higher frequencies. However, the lowest return loss point for each chemical potential is less than -15 dB, meeting the antenna impedance matching requirements. Furthermore, the antenna's operating bandwidth and 3dB axial ratio bandwidth do not vary significantly. The circularly polarized antenna designed in this invention exhibits excellent performance across the adjustable frequency range.

[0033] Figure 6 The following graph shows the antenna gain versus frequency from 5.0 to 7.0 THz, where the modal value l = +1. The antenna maintains a gain of over 14 dBi within the circularly polarized operating bandwidth, with a maximum gain of 15.1 dBi. In this specific operating frequency band, the antenna exhibits excellent radiation capability, efficiently radiating electromagnetic energy.

[0034] The antenna adopts coaxial feeding mode. When the six feeding ports are continuously fed with phase differences of 0°, 30°, 60°, 90°, and 120°, integer-order orbital angular momentum vortex waves with modal values l = 0, +1, and +2 and fractional-order orbital angular momentum vortex waves with l = +0.5 and +1.5 can be generated, as shown in Figure 2. Figure 7As shown in the figure, the integer-order OAM wavefront phase distribution diagram with modal values l = 0, +1, and +2 shows a uniform and clear spiral shape and phase singularity; however, due to the distortion of the phase diagram caused by the superposition of integer states, the fractional-order OAM wavefront phase distribution diagram with modal values l = +0.5 and +1.5 shows an asymmetric spiral structure.

[0035] The following table shows the differences between some published patent solutions and the present invention. Among them, Document 1 is a high-gain, low-sidelobe-level circularly polarized OAM antenna based on amplitude- and phase-controlled superlens loading (CN117039449A), Document 2 is a circularly polarized orbital angular momentum antenna (CN108736154A), and Document 3 is a terahertz circularly polarized on-chip antenna with orbital angular momentum performance (CN115810907A).

[0036]

[0037] The antennas designed in References 1 and 2 both operate in the microwave frequency band. Reference 1 uses a loaded superlens to increase the antenna gain to 15.7 dBi. However, the superlens antenna has the disadvantage of a small operating bandwidth, with its relative bandwidth not reaching 10%, and its structure is not easy to generate orbital angular momentum vortex waves with multi-modal values.

[0038] In summary, compared with other publicly reported circularly polarized orbital angular momentum array antennas operating in the terahertz band, the above design achieves a larger operating bandwidth and circularly polarized axial ratio bandwidth, and achieves higher gain characteristics while being able to generate more modal number orbital angular momentum vortex waves.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A terahertz circularly polarized orbital angular momentum array antenna, characterized in that: The antenna is a left-hand circularly polarized antenna, consisting of 6 antenna units, which are rotationally symmetrically distributed and evenly arranged at a 60° rotation angle to form a circular array antenna; The array antenna includes a graphene patch, an upper dielectric substrate, a metal square parasitic patch, a support post, a metal corner-cut patch, a metal rectangular parasitic patch, a lower dielectric substrate, and a metal ground layer. The graphene patch is located on the upper surface of the upper dielectric substrate, the metal square parasitic patch is located on the lower surface of the upper dielectric substrate, the support post is located between the upper and lower dielectric substrates, the metal corner-cut patch and the metal rectangular parasitic patch are located on the upper surface of the lower dielectric substrate, and the metal ground layer is located on the lower surface of the lower dielectric substrate. A feed port is provided at the center of the bottom edge of the metal corner-cut patch. The antenna adopts a coaxial feeding method. When the six feeding ports are continuously fed with phase differences of 0°, 30°, 60°, 90°, and 120°, integer-order orbital angular momentum vortex waves with modal values l = 0, +1, and +2 and fractional-order orbital angular momentum vortex waves with l = +0.5 and +1.5 are generated.

2. The terahertz circularly polarized orbital angular momentum array antenna according to claim 1, characterized in that: The upper dielectric substrate and the lower dielectric substrate are both circular, made of SiO2, with a radius of 90 μm; the thickness of the upper dielectric substrate is 0.5 μm, the thickness of the lower dielectric substrate is 1.5 μm, and the gap between the upper dielectric substrate and the lower dielectric substrate is 2.5 μm; The relative dielectric constant of the upper dielectric substrate and the lower dielectric substrate is 3.

75.

3. The terahertz circularly polarized orbital angular momentum array antenna according to claim 2, characterized in that: The graphene patch has a side length of 7.65 μm and a square shape; the metal square parasitic patch has a side length of 12.15 μm; the graphene patch is arranged in a circular array with the center of the circular dielectric substrate as the center, the center of the graphene patch is located 60 μm away from the center of the dielectric substrate, and the metal square parasitic patches are arranged in a circular array with the graphene patch as the center.

4. The terahertz circularly polarized orbital angular momentum array antenna according to claim 1, characterized in that: The support pillars are cylindrical, there are 6 of them, made of polyimide, with a relative dielectric constant of 3.5, a bottom circle radius of 0.5 μm, and a height of 2.5 μm. The center of the support pillar is 85 μm away from the center of the dielectric substrate.

5. The terahertz circularly polarized orbital angular momentum array antenna according to claim 4, characterized in that: There are 6 metal corner-cut patches, and the corner-cut patches are distributed in rotational symmetry with a rotation angle of 60°.

6. The terahertz circularly polarized orbital angular momentum array antenna according to claim 5, characterized in that: The distance between the metal corner cut patch and the metal rectangular parasitic patch is 0.2 μm. The two sides of the metal rectangular parasitic patch are 4.85 μm and 7 μm respectively. The metal corner cut patch is a rectangular diagonal cut patch with a side length of 11.8 μm and a cut corner length of 4.8 μm.

7. The terahertz circularly polarized orbital angular momentum array antenna according to claim 5, characterized in that: The feeding port has a diameter of 2.5 μm and a center thereof is 56.175 μm away from the center of the dielectric substrate.

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