A design method of electromagnetic vortex generator for circularly polarized wave

Abstract

The application provides a design method of an electromagnetic vortex generator for circularly polarized waves, and belongs to the technical field of OAM wireless communication. The method comprises the following steps: designing a circularly polarized excitation source for generating vortex or non-vortex circularly polarized incident waves; designing a transmission type artificial electromagnetic material unit, wherein the transmission type artificial electromagnetic material unit adopts a cross-shaped variable cell structure; and designing a transmission array for regulating the phase characteristics of the transmission waves to obtain vortex electromagnetic waves with different phase modes and amplitude characteristics. The application generates or expands the circularly polarized electromagnetic vortex waves from the feed source based on the transmission type artificial electromagnetic material structure, and can generate the circularly polarized orbital angular momentum electromagnetic waves carrying any mode by controlling the array mode of the transmission type artificial electromagnetic material structure. The electromagnetic vortex generator realized by the application has the advantages of simple structure, good radiation performance, weak back radiation, easy processing and convenient debugging.

Description

Technical Field

[0001] This invention belongs to the field of artificial electromagnetic material design and application and OAM wireless communication technology, specifically relating to a design method for an electromagnetic vortex generator for circularly polarized waves. Background Technology

[0002] Nowadays, with the rapid development of wireless communication technology, people's living standards have greatly improved. However, with the continuous increase in wireless terminals and people's demand for higher-speed wireless communication, new technologies are still needed to improve communication rates and spectrum utilization. At this time, Orbital Angular Momentum (OAM) technology, as a brand-new technology, has attracted widespread attention due to its high spectrum utilization and excellent anti-interference capabilities.

[0003] Orbital angular momentum (OAM) of electromagnetic waves was first theoretically proposed in 1909 and experimentally proven in 1936. Orbital angular momentum differs from spin angular momentum (SAM). Spin angular momentum has only two modes: left-handed circular polarization and right-handed circular polarization (corresponding to -1 and 1 modes respectively). In contrast, orbital angular momentum has an infinite number of eigenstates. Each OAM state can be defined by a quantum topological charge, which can take any integer value. Furthermore, the electromagnetic waves of these different OAM states are pairwise orthogonal and can maintain a stable phase structure during independent transmission. Theoretically, within a fixed frequency band, this new technique of orbital angular momentum can realize the transmission of an infinite number of signals. At the same time, orbital angular momentum exhibits good electromagnetic compatibility. Therefore, the application of this new technique of electromagnetic wave orbital angular momentum provides an effective solution to the current problem of scarce spectrum resources and is expected to greatly improve the capacity of communication systems. The development of this technology has broad prospects.

[0004] As mentioned above, spin angular momentum, i.e., the polarization of electromagnetic waves, especially circular polarization, also has its value in practical engineering. For example, it has the ability to resist multipath fading in complex platforms or communication scenarios. Therefore, combining circularly polarized electromagnetic waves with orbital angular momentum and proposing a circularly polarized orbital angular momentum generator implementation scheme with a simple design process and easy implementation has great application value for future wireless communication.

[0005] Chinese patent application CN201810919465.5 discloses a dual-polarization, dual-mode electromagnetic vortex generator. The excitation source in this patent is linearly polarized, not circularly polarized, and the resulting vortex wave is still a linearly polarized wave. Furthermore, the realization of the vortex wave in this patent relies entirely on phase control on a transmission plate; the transmission plate itself does not have the ability to increase or decrease the mode order. Summary of the Invention

[0006] To address the aforementioned technical problems, the purpose of this invention is to provide a design method for an electromagnetic vortex generator for circularly polarized waves, capable of generating orbital angular momentum waves with good radiation performance and weak back radiation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A design method for an electromagnetic vortex generator for circularly polarized waves includes the following steps:

[0009] Step 1: Design a circularly polarized excitation source to generate vortex or non-vortex circularly polarized incident waves.

[0010] Step 2: Design the transmissive artificial electromagnetic material unit. The transmissive artificial electromagnetic material unit adopts a cross-shaped deformable unit structure.

[0011] Step 3: Design a transmission array and adjust the phase characteristics of the transmitted wave to obtain vortex electromagnetic waves with different phase modes and amplitude characteristics.

[0012] Optionally, the circularly polarized excitation source is a vortex wave horn or a UCA array, capable of radiating circularly polarized electromagnetic waves of a specific order in vortex form.

[0013] Optionally, the equivalent phase center of the circularly polarized excitation source is located near the equivalent focal length of the planar transmission array, and the size of the transmission array is capable of intercepting the main radiated power radiated by the circularly polarized excitation source.

[0014] Optionally, the central region of the transmission array may be removed based on the amplitude of the primary wave of the circularly polarized excitation source.

[0015] Optionally, the transmissive artificial electromagnetic material unit is a printed circuit design, employing a cross-shaped deformable unit. The metal arm of the simple cross unit is replaced by a bent line structure, and the width of the bent line structure is changed to satisfy the Pancharatnam-Berry phase principle. The phase of the transmitted wave is compensated by controlling the in-plane rotation angle of the transmissive artificial electromagnetic material unit.

[0016] Optionally, by controlling the size of the transmissive artificial electromagnetic material unit, different amplitudes of transmitted waves can be obtained in different local areas, thereby achieving amplitude weighting and controlling the beam shape of the transmitted wave.

[0017] Optionally, the transmissive artificial electromagnetic material unit adopts a multi-layer composite structure design, thereby having a phase adjustment capability covering 0°-360°.

[0018] Optionally, the circularly polarized excitation source adopts conventional circularly polarized horn, microstrip antenna, or helical antenna forms, corresponding to the 0th order vortex wave, and the central region of the transmission array also adopts a non-removal design.

[0019] Optionally, in the absence of a continuous metal ground, the transmissive artificial electromagnetic material unit may adopt a patch-type or porous structure.

[0020] The present invention has the following advantages:

[0021] 1. This invention generates or extends circularly polarized electromagnetic vortex waves originating from a feed source based on a transmissive artificial electromagnetic material structure. It can generate circularly polarized orbital angular momentum electromagnetic waves that can carry arbitrary modes by controlling their array configuration, and can be used for wireless communication.

[0022] 2. The spatial array of the present invention increases the aperture size, has good radiation performance, and weak back radiation.

[0023] 3. By using the method of the present invention, when the feed source itself radiates vortex waves, the central area of ​​the transmission array does not need to be equipped with units or adopt a hollowed-out design, which can further reduce costs.

[0024] 4. The electromagnetic vortex generator realized by the present invention has a simple structure, is easy to process and easy to debug. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the principle of an electromagnetic vortex generator.

[0026] Figure 2 A schematic diagram (top view) of a transmissive artificial electromagnetic material unit.

[0027] Figure 3 A schematic diagram (side view) of the design of a transmissive artificial electromagnetic material unit;

[0028] Figure 4 A schematic diagram of the structure of a UCA microstrip antenna array that generates a circularly polarized vortex wave excitation source;

[0029] Figure 5 This is a schematic diagram of an electromagnetic vortex generator.

[0030] Figure 6 The phase distribution diagram of the ρ component of the radiated electric field parallel to the vortex array is given when the vortex mode is 1.

[0031] Figure 7The electric field radiated parallel to the vortex array is given when the vortex mode is 1. Phase distribution diagram of the components;

[0032] Figure 8 The amplitude distribution of the radiated electric field parallel to the vortex array is given when the vortex mode is 1. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] A design method for an electromagnetic vortex generator for circularly polarized waves is proposed. Based on the orbital angular momentum (OAM) beam generation method using a transmissive artificial electromagnetic material structure, the design of the electromagnetic vortex generator mainly consists of three parts:

[0035] The first part is the design of vortex or non-vortex circularly polarized excitation sources to generate vortex or non-vortex circularly polarized incident waves.

[0036] The second part is the design of a transmissive artificial electromagnetic material unit. This transmissive artificial electromagnetic material structure consists of dielectric attachment, embedded single-layer or multi-layer metal patches or pores. It can adopt a deformable cross unit, and use a bent line structure to replace the metal arms or metal grooves of the traditional cross unit. By changing the width of the bent line structure, it can satisfy the Pancharatnam-Berry phase principle. Under circularly polarized wave excitation, by controlling the in-plane rotation angle of the designed unit, the transmission phase of the electromagnetic wave can be effectively controlled within the range of 0 to 360 degrees.

[0037] The third part is the design of vortex arrays based on transmissive artificial electromagnetic materials. The designed artificial electromagnetic material units are arrayed, and the rotation angle and size of the units at different positions in the plane are adjusted to control the local phase and amplitude characteristics of the transmitted wave, and finally obtain vortex electromagnetic waves with higher order and specific amplitude distribution.

[0038] Among them, the circularly polarized excitation source itself can radiate circularly polarized electromagnetic waves in the form of vortices of a specific order, specifically vortex wave horns, UCA arrays, etc.

[0039] The equivalent phase center of the circularly polarized excitation source is located near the equivalent focal length of the planar transmission array, and the size of the transmission array should be able to intercept the main radiated power radiated by the circularly polarized vortex wave excitation source, for example, based on the outer beamwidth of 10 dB power.

[0040] The amplitude of the primary wave of the visible circularly polarized excitation source in the central region of the transmission array can be removed, for example, based on the irradiation range of the inner beamwidth of the 10dB power, thereby achieving lower costs in the printing and manufacturing process during the implementation stage.

[0041] The transmissive artificial cell is a printed circuit design, employing a cross-shaped deformable cell. A bent-line structure effectively replaces the metal arm of a simple cross-shaped cell, and by changing the width of the bent-line structure, it satisfies the Pancharatnam-Berry phase principle. The phase of the transmitted wave can be compensated accordingly by controlling the in-plane rotation angle of the control unit. Based on this principle, vortex arrays can be designed to more easily control the mode order of vortex waves, especially achieving higher orders. For example, a circularly polarized excitation source illuminates a first-order vortex wave, but through a transmissive array, an additional one or N-order phase shift can be added to achieve a second-order or N+1-order mode; of course, mode order reduction is also possible.

[0042] The size of the transmissive artificial unit can also be controlled, thereby obtaining different transmitted wave amplitudes in different local areas, realizing amplitude weighting, and facilitating the control of the beam shape of the transmitted wave;

[0043] The artificial electromagnetic material unit adopts a multi-layer composite structure design, which gives it a greater phase adjustment capability, such as covering 0°-360°; at the same time, the multi-layer composite structure also achieves a greater operating bandwidth.

[0044] The circularly polarized excitation source can also be a conventional circularly polarized horn, microstrip antenna, helical antenna, etc., corresponding to the 0th order vortex wave, so the central region of the transmission array can also be designed without removal.

[0045] Furthermore, in the absence of a continuous metal ground, the transmissive artificial electromagnetic material unit can be either a patch type or a porous type.

[0046] Figure 1 The figure shows a schematic diagram of the electromagnetic vortex generator implemented by this method. As can be seen from the figure, the excitation wave of the circularly polarized excitation source and the transmitted wave carrying the orbital angular momentum are located on both sides of the generator, which can reduce the influence of the circularly polarized excitation source on the vortex wave; the metasurface structure is a stacked structure, which can achieve high transmission efficiency and a wide phase adjustment range.

[0047] Figure 2 The diagram shows a top view of the metasurface element design structure, which is derived from a deformed metal cross-shaped patch. The element design is achieved by changing the width of the bend line that effectively replaces the metal arm. The center frequency of this embodiment is 7.4 GHz, and the corresponding dimensional values ​​are shown in Table 1 below.

[0048] Table 1 Structural Dimensions of Example 1

[0049]

[0050] Figure 3The image shows a side view of the metasurface unit design structure. This example consists of one dielectric layer and two metal layers, which can meet the requirements of transmission efficiency and phase adjustment. The thickness of the dielectric layer is t = 6.4 mm.

[0051] Figure 4 The diagram shows a UCA microstrip antenna array that realizes a circularly polarized vortex wave excitation source.

[0052] like Figure 5 The diagram shows the structure of the electromagnetic vortex generator implemented by this method. This embodiment is based on the generator implementation scheme of transmissive artificial electromagnetic materials. Structurally, it is divided into three parts: the first part is a circularly polarized microstrip UCA array excitation source, which is used to generate a circularly polarized incident wave source; the second part is the design of transmissive artificial electromagnetic material unit, which adopts a cross-shaped deformable unit structure; the third part is the vortex array design, which controls the phase characteristics of the transmitted wave to obtain vortex electromagnetic waves.

[0053] Figure 6 The phase distribution diagram of the ρ component of the radiated electric field parallel to the vortex array is given when the vortex mode is 1. As can be seen from the figure, the phase of the electric field is counterclockwise vortex-shaped along the azimuth of the axis, and the phase changes around the circumference. This is the first-order OAM.

[0054] Figure 7 The electric field radiated parallel to the vortex array is given when the vortex mode is 1. Phase distribution diagram of the components. As can be seen from the diagram, the electric field phase exhibits a counterclockwise vortex shape along the azimuth of the axis, changing phase around the circumference; this is the first-order OAM.

[0055] Figure 8 The amplitude distribution of the radiated electric field parallel to the vortex array is given when the vortex mode is 1.

[0056] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A design method for an electromagnetic vortex generator for circularly polarized waves, characterized in that, Includes the following steps: Step 1: Design a circularly polarized excitation source to generate vortex or non-vortex circularly polarized incident waves; the circularly polarized excitation source adopts the form of a circularly polarized horn, microstrip antenna or helical antenna, corresponding to the 0th order vortex wave, and the central region of the transmission array adopts a non-removal design. Step 2: Design the transmissive artificial electromagnetic material unit. The transmissive artificial electromagnetic material unit is a printed circuit design. The transmissive artificial electromagnetic material unit adopts a cross-shaped deformable unit structure. The metal arm of the simple cross unit is replaced by a bent line structure. By changing the width of the bent line structure, it can satisfy the Pancharatnam-Berry phase principle. The phase of the transmitted wave is compensated by controlling the in-plane rotation angle of the transmissive artificial electromagnetic material unit. Step 3: Design the transmission array. The central region of the transmission array is designed to be removed based on the amplitude of the primary wave of the circularly polarized excitation source. The phase characteristics of the transmitted wave are adjusted to obtain vortex electromagnetic waves with different phase modes and amplitude characteristics.

2. The design method for an electromagnetic vortex generator for circularly polarized waves according to claim 1, characterized in that, The circularly polarized excitation source is a vortex wave horn or a UCA array.

3. The design method for an electromagnetic vortex generator for circularly polarized waves according to claim 1, characterized in that, The equivalent phase center of the circularly polarized excitation source is located near the equivalent focal length of the planar transmission array, and the size of the transmission array is sufficient to intercept the main radiated power radiated by the circularly polarized excitation source.

4. The design method for an electromagnetic vortex generator for circularly polarized waves according to claim 1, characterized in that, By controlling the size of the transmissive artificial electromagnetic material unit, different amplitudes of transmitted waves can be obtained in different local areas, thereby achieving amplitude weighting and controlling the beam shape of the transmitted wave.

5. The design method for an electromagnetic vortex generator for circularly polarized waves according to claim 1, characterized in that, The transmissive artificial electromagnetic material unit adopts a multi-layer composite structure design, thus having a phase adjustment capability covering 0°-360°.

6. The design method for an electromagnetic vortex generator for circularly polarized waves according to claim 1, characterized in that, Without a continuous metal ground, the transmissive artificial electromagnetic material unit adopts a patch-type or porous structure.

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