A microstrip antenna using orbital angular momentum of graphene

Abstract

The application discloses a kind of track angular momentum microstrip antennas using graphene, including dielectric substrate, the lower surface of the dielectric substrate is equipped with ground metal layer, the upper surface of the dielectric substrate is equipped with annular graphene layer and metal patch, the metal patch is inside annular graphene layer, 4 feed ports are uniformly arranged on the metal patch, the feed port penetrates metal patch, dielectric substrate and ground metal layer.This antenna is light in quality, simple in structure, easy to process and only needs to adjust the phase difference of feed to produce stable modal number l=-2, 0 and +2 orbital angular momentum vortex wave, in addition, by adding graphene material, the performance is more excellent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of orbital angular momentum antennas, and mainly relates to a graphene microstrip antenna of orbital angular momentum. BACKGROUND

[0002] Nowadays, the mobile Internet is rapidly growing, and mobile terminals are widely popularized, and spectrum resource shortage again becomes a big problem in the field of wireless communication. In order to overcome this problem, there are mainly two methods to improve the system capacity: (1) developing new spectrum resources. For example, using higher frequency electromagnetic wave communication. (2) Using new technology to improve the spectrum utilization rate. For example, the advanced technologies such as simultaneous full duplex and large-scale multiple-input multiple-output used in 5G mobile communication system. But these means only use the polarization, amplitude, frequency and phase of the signal as four degrees of freedom to modulate information, which all belong to the linear degrees of freedom of electromagnetic wave.

[0003] According to the classical electromagnetic theory, the momentum of electromagnetic wave has two kinds of linear momentum and angular momentum, and the angular momentum can be divided into spin angular momentum (SAM) and orbital angular momentum (OAM). SAM is related to the polarization state of electromagnetic wave, mainly manifested as left-handed circular polarization, right-handed circular polarization and linear polarization; OAM is related to the spatial phase distribution of electromagnetic wave. After that, people found that the multiplexing communication system based on orbital angular momentum has orthogonality, high spectrum utilization rate, high transmission rate and multi-dimensionality compared with the traditional system. The academia has proved through experiments that the mode multiplexing of orbital angular momentum vortex wave is a new kind of multiplexing mode. Therefore, the discovery of orbital angular momentum provides a new solution direction for improving the spectrum utilization rate and system capacity.

[0004] Graphene is a two-dimensional super material formed by honeycomb-shaped arrangement of single-layer carbon atoms in the same plane, and is widely used in electromagnetic and other fields because of its excellent material properties. It has excellent electrical, thermal, mechanical and optical properties, and the electrical conductivity is adjustable.

[0005] With the in-depth study of orbital angular momentum, there are more and more ways to generate orbital angular momentum, such as using antenna array, reflector antenna and super surface antenna, but most of the orbital angular momentum antennas have problems such as complex structure, high processing precision requirement and complex operation to change the mode. SUMMARY

[0006] The application aims to provide a graphene microstrip antenna capable of generating orbital angular momentum, which is light in quality, simple in structure, easy to process, and only needs to adjust the feed phase difference to generate stable orbital angular momentum vortex waves with mode numbers l=-2, 0 and +2, and the performance is more excellent by adding graphene material.

[0007] In order to achieve the above object, the solution of the present application is:

[0008] An orbital angular momentum microstrip antenna using graphene, the antenna comprises a dielectric substrate, the lower surface of the dielectric substrate is provided with a grounding metal layer, the upper surface of the dielectric substrate is provided with a ring-shaped graphene layer and a metal patch, the metal patch is located inside the ring-shaped graphene layer, 4 feeding ports are uniformly arranged on the metal patch, and the feeding ports penetrate through the metal patch, the dielectric substrate and the grounding metal layer.

[0009] Further, the dielectric substrate is circular, with a radius of 40mm and a thickness of 1mm.

[0010] Further, the metal patch is ring-shaped, with an inner radius of 6.8mm and an outer radius of 16mm.

[0011] Further, the inner radius and the outer radius of the graphene layer are 20mm and 40mm respectively.

[0012] Further, the graphene temperature T of the graphene layer is 300K, the chemical potential μ is 0.9eV, and the relaxation time τ is 1ps. c

[0013] Further, the 4 feeding ports are circular, with a radius of 1.5mm, and the distance e between the center of each feeding port and the center of the metal patch is 11.4mm.

[0014] Further, the antenna adopts a coaxial feeding mode, when the continuous phase difference of the 4 feeding ports is 90° or -90°, a vortex wave with mode number l=-2 or +2 is generated; when the continuous phase difference of any two opposite feeding ports is 180°, a vortex wave with mode number l=0 is generated.

[0015] Further, there is a gap between the graphene layer and the metal patch.

[0016] Compared with the prior art, the present application has the following advantages: by adding graphene, the performance of the present application is more superior than that of the orbital angular momentum microstrip antenna without graphene, the feeding port can achieve better impedance matching and energy output, and the present application has smaller return loss; the antenna designed in the present application can generate stable OAM vortex waves with mode numbers l=-2, 0 and +2 by adjusting the feeding phase difference; the antenna designed in the present application has a simple structure, easy mode change, and good vortex wave characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural diagram of the antenna of the present application, wherein 1-4 in the figure are 4 feeding ports. ​

[0018] Figure 2 is a cross-sectional view of the antenna of the present invention;

[0019] Figure 3 The return loss S of the antenna using graphene material and the metal antenna without graphene material is 11 Parameter comparison chart;

[0020] Figure 4 are the vortex wave phase diagrams of different modes at 14.9 GHz, where (a) is the vortex wave phase diagram when the mode number is -2; (b) is the vortex wave phase diagram when the mode number is 0; (c) is the vortex wave phase diagram when the mode number is +2;

[0021] Figure 5 is the S of the antenna at different chemical potentials of graphene 11 parameter;

[0022] Figure 6 These are the wavefront phase diagrams of the vortex wave with mode number l = -2 when working at different graphene chemical potentials at 14.9 GHz, where (a) is the wavefront phase diagram of the vortex wave with mode number l = -2 when the chemical potential is equal to 0.1 eV; (b) is the wavefront phase diagram of the vortex wave with mode number l = -2 when the chemical potential is equal to 0.3 eV; (c) is the wavefront phase diagram of the vortex wave with mode number l = -2 when the chemical potential is equal to 0.5 eV; (d) is the wavefront phase diagram of the vortex wave with mode number l = -2 when the chemical potential is equal to 0.7 eV; and (e) is the wavefront phase diagram of the vortex wave with mode number l = -2 when the chemical potential is equal to 0.9 eV. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] like Figure 1 and 2 As shown, an embodiment of the present invention is an orbital angular momentum microstrip antenna using graphene, which is composed of a graphene layer, a metal patch, a dielectric substrate, a grounded metal layer, and a feed port. The graphene temperature of the graphene layer is T = 300K, and the chemical potential μ is c=0.9eV, relaxation time τ =1ps, annular shape, inner and outer radii a = 20mm and b = 40mm respectively; the metal patch is a circular ring, with inner and outer radii c = 6.8mm and d = 16mm respectively, placed on the upper surface of the dielectric substrate, in the same plane as the graphene layer; the dielectric substrate is placed between the metal patch and the grounded metal layer, in a circular shape, with a radius and thickness r = 40mm and h = 1mm respectively; the grounded metal layer is the same shape and size as the dielectric substrate and is placed on the lower surface of the dielectric substrate; the four feeding ports of the antenna are all circular, with a radius of 1.5mm, and the distance from the center of the port to the center of the structure is e = 11.4mm, evenly distributed on the metal patch, throughout the entire structure. After the structural design is completed, the feeding ports are fed with different phases using coaxial feeding to excite vortex waves: when the four feeding ports are fed with a continuous phase difference of 90° or -90°, vortex waves with a modal number of l = -2 or +2 can be generated; when the feeding ports 1 and 3 (or feeding ports 2 and 4) are fed with a continuous phase difference of 180°, a vortex wave with a modal number of l = 0 can be generated.

[0025] To verify the performance improvement after adding graphene, the graphene material of the graphene layer was replaced with metal and then simulated and compared with the performance of the two antennas. When the input impedance is set to 50Ω, the impedance matching is good, which can effectively reduce the energy reflection (i.e., return loss) in each coaxial feed port. After completing the impedance matching, the power of each of the four feed ports is set to 1W. Because the designed orbital angular momentum antenna structure is highly symmetrical, only the return loss of feed port 1 needs to be simulated. The simulated return loss is S 11 The parameters are Figure 3 The center frequencies of the graphene OAM antenna and the metal OAM antenna are both around 14.9 GHz. When the antenna works at the center frequency, the S 11 Only -23dB, while the S of graphene OAM antenna 11 It reached -47dB, a decrease of 24dB, indicating that the feeding port of the graphene OAM antenna achieved better impedance matching and energy output, and the antenna performance was optimized.

[0026] Furthermore, the wavefront phase distribution and mode number are the two most important indicators of the generation of orbital angular momentum vortex waves. The far-field phase distribution diagram of the antenna designed by the present invention is obtained by simulation as follows: Figure 4 shown. Figure 4The (a) in the figure is a phase diagram generated by phase-continuous phase difference 90 DEG orthogonal feeding of four feeding ports, two clockwise helical phase curves can be seen in the figure, and the phase of the two curves changes by 360 DEG, and there is a center phase singularity, corresponding to the vortex beam of mode number l=-2, the result shows that the phase of the electromagnetic wave front radiated out changes helically with the spatial azimuth angle, and the graphene orbital angular momentum antenna designed in the application can generate vortex waves with good performance; Figure 4 The (b) in the figure is a phase diagram generated by phase-continuous phase difference 180 DEG orthogonal feeding of feeding ports 1 and 3 (or feeding ports 2 and 4), a ring formed by helical phase can be clearly seen in the figure, and the phase of the ring changes by 360 DEG, and there is a center phase singularity, corresponding to the vortex wave of mode number l=0. Figure 4 The (c) in the figure is a phase diagram generated by phase-continuous phase difference-90 DEG orthogonal feeding of four feeding ports, two counterclockwise helical phase curves can be seen in the figure, and the phase of the two curves changes by 360 DEG, and there is a center phase singularity, corresponding to the vortex wave of mode number l=+2. In summary, the graphene orbital angular momentum antenna designed in the application can generate stable vortex waves of mode number l=-2, 0 and +2.

[0027] The chemical potential of graphene can be changed by applying a bias magnetic field or an electric field at both ends of the graphene, and the change of the chemical potential of graphene will affect the performance of the antenna, so the performance of the antenna can be improved by adjusting the chemical potential of graphene. The simulation obtains the change of the S 11 parameters of the antenna with the chemical potential, as shown in the figure. Figure 5 When the chemical potential is 0.9eV, the S 11 of the graphene orbital angular momentum antenna is-47dB, and at this time, the performance of the antenna is significantly optimized compared with the antenna when the chemical potential is 0.1eV. Therefore, the performance of the graphene orbital angular momentum antenna designed in the application can be optimized by adjusting the chemical potential of graphene.

[0028] Meanwhile, the influence of the chemical potential of graphene on the mode number and wave front phase of the excited vortex wave also needs to be studied. Since the mode number l=0 of the vortex wave generated by the designed graphene orbital angular momentum antenna corresponds to a plane wave, the helical phase distribution cannot be observed, so only the vortex wave of mode number l=±2 needs to be studied, and the helical phase values of the two vortex waves are the same and the directions are opposite, so only one of the mode numbers needs to be studied, and here the vortex wave of mode number l=-2 is studied, and the simulation result is as shown in the figure. Figure 6It can be seen that the change of the chemical potential of graphene does not affect the mode number and wavefront phase of the vortex wave. The mode number of the vortex wave excited by the orbital angular momentum antenna is very stable, and even if the inevitable electromagnetic divergence and energy loss occur in the antenna during radiation, the mode number of the vortex wave will remain unchanged.

[0029] The above examples are used to explain and illustrate the present application, but not to limit the present application, and any modification and change made to the present application within the spirit and protection scope of the claims of the present application, falls into the protection scope of the present application.

Claims

1. An orbital angular momentum microstrip antenna using graphene, characterized in that: The antenna includes a dielectric substrate, a grounded metal layer is provided on the lower surface of the dielectric substrate, an annular graphene layer and a metal patch are provided on the upper surface of the dielectric substrate, the metal patch is located inside the annular graphene layer, a gap exists between the graphene layer and the metal patch, and four feeding ports are evenly distributed on the metal patch, and the feeding ports penetrate the metal patch, the dielectric substrate and the grounded metal layer; The antenna adopts coaxial feeding mode, and when the four feeding ports are fed with continuous phase difference of 90° or -90°, the modal data generated is l =-2 or +2 vortex wave; When any two opposite feeding ports are continuously fed with a phase difference of 180°, the modal number generated is l= 0 vortex wave.

2. The orbital angular momentum microstrip antenna using graphene according to claim 1, characterized in that: The dielectric substrate is circular with a radius of 40 mm and a thickness of 1 mm.

3. The orbital angular momentum microstrip antenna using graphene according to claim 1, characterized in that: The metal patch is annular, with inner and outer radii of 6.8 mm and 16 mm respectively.

4. The orbital angular momentum microstrip antenna using graphene according to claim 1, wherein: The inner and outer radii of the graphene layer are 20 mm and 40 mm respectively.

5. The orbital angular momentum microstrip antenna using graphene according to claim 1, characterized in that: The graphene temperature of the graphene layer T =300K, chemical potential μ c =0.9eV, relaxation time τ =1ps.

6. The orbital angular momentum microstrip antenna using graphene according to claim 1, characterized in that: The four feeding ports are all circular with a radius of 1.5 mm. The distance from the center of each feeding port to the center of the metal patch is e =11.4mm.

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