Design method of multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity

Abstract

This invention discloses a design method for a multi-subarray orbital angular momentum antenna with hybrid spatial / modal diversity. First, the method ignores the mutual coupling effect between subarrays and derives an expression for spatial diversity and a design range for structural parameters under effective transmission distance. Then, based on the mutual coupling effect, the method studies the modal aliasing and impact of subarrays on different spatial diversities. Finally, by optimizing factors such as subarray size and array spacing, a compact orbital angular momentum antenna with optimal transmission performance is obtained. This method minimizes the aliasing effect between beams and achieves high-purity, low-aliasing characteristics of the vortex beam.

Description

Technical Field

[0001] The present invention relates to the field of antennas, and in particular to a design method for a multi-subarray orbital angular momentum antenna with space / modal hybrid diversity. Background Art

[0002] With the rapid development of wireless communications and the dramatic increase in various demands, spectrum resource shortages are becoming increasingly severe. In addition to spatial multiplexing, time multiplexing, and frequency division multiplexing, mode division multiplexing (MDM) using orbital angular momentum (OAM) is becoming increasingly popular. The orthogonality between modes theoretically allows for an infinite number of modes within the same frequency band, making OAM a promising new solution to spectrum constraints.

[0003] Methods for generating OAM vortex waves include spiral phase plates, metasurfaces, and single antennas. However, these methods struggle to generate multimode OAM waves, leading to inherent limitations in wireless communication systems. Uniform circular arrays (UCA antennas) are another popular method for generating OAM waves due to their simple structure, ease of phase control, low cost, and flexibility in generating multimodal OAM waves.

[0004] Currently, metasurface antennas are very convenient for generating multimodal OAM waves. However, they can only generate vortex waves of different modes in multiple directions or different vortex waves in different frequency bands, and high purity requires a large size. An antenna that can generate multiple beams with diverse mode combinations and parallel transmission has considerable research value. Summary of the Invention

[0005] The purpose of the present invention is to provide a design method for a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity. The antenna designed by this method minimizes crosstalk between beams as much as possible while realizing coplanar parallel emission of multiple vortex beams, thereby achieving high purity and low aliasing characteristics of the vortex beams.

[0006] The technical solution for achieving the purpose of the present invention is:

[0007] A design method for a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity comprises the following steps:

[0008] S1. Based on the preliminary simulation of the field radiation formula of the UCA antenna, a UCA antenna circular array model with different modes is established, the observation plane is divided, and the electric field amplitude, phase and mode purity of each part are obtained respectively.

[0009] S2. Ignore the mutual coupling effect between subarrays and derive the expression for the total spatial / modal hybrid diversity based on the UCA antenna radiation formula. By setting an effective transmission distance (i.e., the distance within which the purity of the vortex wave can reach a certain value), multiple calculations are performed to determine the modal aliasing and interference between subsets in the spatial / modal hybrid diversity method, and to find the effective range of parameters such as the UCA antenna radius, the number of array elements, and the spacing between adjacent subarrays.

[0010] S3. Based on the rough parameters obtained above, circular array models of different modes are simulated in the simulation software CST, and placed on the same plane. Parameter scanning is performed to obtain the optimal circular array parameters and sub-array spacing corresponding to the required effective transmission distance while considering the coupling of adjacent subsets.

[0011] Furthermore, the UCA circular array models of different modes are established in step S1 as follows: a fixed phase difference is added to each unit in the UCA antenna unit radiation formula in a clockwise order, and then superimposed to form UCA antenna radiation formulas of different modes. These formulas are then superimposed according to the sub-array position relationship and mode combination to obtain the UCA antenna circular array model.

[0012] Furthermore, the UCA circular array model of different modes is established in step S1 as follows: in the UCA antenna unit radiation formula, each unit is added with a fixed phase difference in clockwise order (counterclockwise and clockwise are both possible, corresponding to +1 and -1 modes respectively), and then superimposed to form the UCA antenna radiation formula of different modes, and then these formulas are superimposed according to the sub-array position relationship and mode combination to obtain the UCA antenna circular array model.

[0013] Furthermore, in step S2, the mutual coupling effect between subarrays is ignored, and the overall spatial / modal hybrid diversity is derived based on the UCA antenna radiation formula as follows: assuming that the antenna array is composed of antennas located at different positions, the radiation field is controlled by the vector current moment, the vector current of each unit is time-sequenced and linearly phase modulated, and finally, the relationship between the effective current and the radiation pattern of each subarray is obtained after convolution processing;

[0014] Furthermore, the spatial / modal hybrid diversity refers to dividing the space into multiple regions, each region serving as a subset of the antenna's active area, and mainly generating a single-mode vortex wave within a certain transmission distance. The space can be divided into four regions along the Z axis with the X and Y axes as boundaries, and the distance between the center points of adjacent sub-arrays is defined as the sub-array spacing, thereby generating four parallel orbital angular momentum beams propagating along the Z axis.

[0015] Furthermore, the single-mode vortex waves generated by each subset are subject to interference from other subsets. By adjusting the structure of each subset and controlling its power, we can effectively control the problem of large differences in the radiation field values ​​and reduce the aliasing effect between subsets. Adjusting the subarray spacing further controls the effective transmission distance; the effective transmission distance refers to the distance within which the vortex waves generated by the subsets maintain high purity.

[0016] Furthermore, in step S2, multiple calculations are performed to determine the modal aliasing and impact of the subarray on different spatial diversities, and to obtain the effective range of the UCA antenna circular array parameters and the spacing between adjacent subarrays. Specifically, the relationship between the effective current and the radiation pattern of the subarrays with different spatial diversities is determined using the effective current of the antenna and the UCA antenna radiation field formula. By adjusting the parameters, the range of the UCA antenna circular array parameters and the spacing between adjacent subarrays that meets the purity requirements and the effective transmission distance is obtained.

[0017] Furthermore, step S3 specifically involves establishing circular array models of different modes in the simulation software CST and placing them on the same plane. A parameter sweep is performed to find the parameter combination that produces the highest purity OAM waves within the effective transmission distance in the simulation results, thereby determining the optimal circular array parameters and the spacing between adjacent subarrays.

[0018] Compared with the prior art, the present invention has the following beneficial contributions:

[0019] (1) Using spatial / modal hybrid diversity to establish the approximate range through data analysis and software parameter scanning to process the influence of the coupling effect between sub-arrays, a multi-sub-array antenna that transmits high-purity vortex waves within the effective transmission distance can be designed more accurately according to the needs;

[0020] (2) By adjusting the radius of the UCA antenna, the energy difference between modes is effectively reduced, which prevents the high-mode vortex wave from being masked by the low-mode vortex wave at the same distance due to its low energy;

[0021] (3) While keeping the overall size small, the need to maintain high purity of vortex waves within a certain distance is solved by increasing the spacing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow diagram of the method of the present invention.

[0023] Figure 2 It is a schematic diagram of four square-arranged circular array antennas of the present invention.

[0024] Figure 3 (a) and Figure 3 (b) are the electric field amplitude diagram and phase diagram simulated by the present invention.

[0025] Figure 4 (a) and Figure 4 (b) are the electric field phase diagram and far-field diagram of the simulation test of the present invention. DETAILED DESCRIPTION

[0026] The following examples are provided to further explain and supplement the present invention and do not constitute any limitation to the present invention.

[0027] like Figure 1 A method for designing a coplanar multimode multibeam vortex wave antenna comprises the following steps:

[0028] S1. Based on the preliminary simulation of the field radiation formula of the UCA antenna, a UCA antenna circular array model with different modes is established, the observation plane is divided, and the electric field amplitude, phase and mode purity of each part are obtained respectively.

[0029] S2. Ignore the mutual coupling effect between subarrays and derive the expression for the total spatial / modal hybrid diversity based on the UCA antenna radiation formula. By setting an effective transmission distance (i.e., the distance within which the purity of the vortex wave can reach a certain value), multiple calculations are performed to determine the modal aliasing and interference between subsets in the spatial / modal hybrid diversity method, and to find the effective range of parameters such as the UCA antenna radius, the number of array elements, and the spacing between adjacent subarrays.

[0030] S3. Based on the rough parameters obtained above, circular array models of different modes are simulated in the simulation software CST, and placed on the same plane. Parameter scanning is performed to obtain the optimal circular array parameters and sub-array spacing corresponding to the required effective transmission distance while considering the coupling of adjacent subsets.

[0031] like Figure 2 As shown, the embodiment is four square-shaped circular array antennas, numbered 1, 2, 3, and 4 from upper left to lower right. Each circular array consists of eight simple patches, which are fed by coaxial lines, and the feeding phase is set according to the vortex factor.

[0032] With the center point of each circular array as the center of a small area, and the center point of the overall structure and the X and Y coordinate axes as boundaries, the entire space is divided into four small areas. A different mode of vortex wave is realized in each area, thus forming a two-unit sub-array.

[0033] The commercial electromagnetic simulation software CST Studio Suite was used for simulation calculations and optimization design to ensure that the gain, mode purity, and frequency of each antenna were as consistent as possible. The present invention used CST to first simulate and optimize the performance of each UCA antenna and then simulate and verify the overall structure.

[0034] From the perspective of effective current of the sub-array, the theoretical analysis is carried out. The effective current of the sub-array can be expressed as:

[0035]

[0036] Where m represents the mode of the sub-matrix, Represents the support domain of the transformation to the nth unit to the origin, is the vector electric distance representing the radiation field, g m,0,Mod UCA circular array The phase factor is the expression after Fourier transform of the azimuth angle φ, j is the imaginary number, k is the wave number, θ is the pitch angle, ρ′ Mod Represents the radius of the UCA circle array;

[0037] The relationship between the directivity pattern of the sub-array and the effective current is deduced,

[0038]

[0039] Among them, the integral term represents the vector electric distance, represents a direction vector, is the superposition of the effective current of N units in the mth subarray plus the phase factor, F θ (l) is the far-field directional function of the UCA with mode l, which can be expanded in detail as follows:

[0040]

[0041] A mathematical model is established to roughly estimate the sub-array structure data, taking the 1, 1, 1, -1 pattern combination as an example. Figure 3 (a) and Figure 3 (b) are the electric field amplitude diagram and phase diagram obtained by modeling and simulation. If the distance between UCA antennas is too close, there will be mutual interference, the phases of the four vortices will be chaotic and the amplitudes will no longer be four obvious circles. If the spacing is too high, the size of the overall structure will increase, which will waste simulation time.

[0042] Import the parameter range obtained above into the CST simulation software to optimize the parameter sweep. Under the premise of setting the observation distance, the purity of the vortex wave in each area is tested. Taking the mode combination of 1, -1, 1, -1 as an example, Figure 4 (a) and Figure 4 (b) are the electric field phase diagram and far field diagram of the simulation test, Figure 4 Four vortex waves can be clearly observed in the image. Their purity varies, which may be related to the phase feeding combination of the unit. However, the purity has reached more than 60%, indicating that the scheme is feasible.

[0043] It is also important to note that when using different modes for array deployment, the vortex wave intensities of different modes can vary significantly, causing the vortex waves of higher modes to be masked by those of lower modes, making it impossible to observe clear vortex characteristics. In this case, it is necessary to adjust the radius and feed power of the UCA antenna to minimize the difference between them.

[0044] The present invention studies a multi-mode multi-beam structure suitable for near-field operation based on the concept of MIMO subarrays. It can vertically divide the space into multiple small areas, generate OAM waves of multiple different modes in these areas, and use uniform circular arrays and subarray formula derivation for simulation optimization to minimize the aliasing effect between beams, achieve high purity and low aliasing characteristics of vortex beams, and enable effective transmission within a certain distance.

Claims

1. A design method for a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity, characterized in that: Including steps: S1. Based on the UCA antenna field radiation formula, a preliminary simulation is performed to establish UCA antenna circular array models of different modes, divide the observation plane, and obtain the electric field amplitude, phase, and mode purity of each part; S2. Ignore the mutual coupling effect between subarrays and derive the total spatial / modal hybrid diversity based on the UCA antenna radiation formula. Set the effective transmission distance, perform multiple calculations to determine the modal aliasing and interference between subarrays in the spatial / modal hybrid diversity scheme, and obtain the effective range of model parameters and the spacing between adjacent subarrays. S3. Based on the effective range of model parameters and adjacent sub-array spacing, simulate the UCA antenna circular array model with different modes using the simulation software CST to obtain the optimal circular array parameters and adjacent sub-array spacing; In step S2, the mutual coupling effect between subarrays is ignored, and the overall spatial / modal hybrid diversity is derived based on the UCA antenna radiation formula as follows: assuming that the antenna array is composed of antennas located at different positions, the radiation field is controlled by the vector current moment, the vector current of each unit is time-sequenced and linearly phase modulated, and finally, the relationship between the effective current and the radiation pattern of each subarray is obtained after convolution processing; In step S2, multiple calculations are performed to determine modal aliasing and interference between subsets in a spatial / modal hybrid diversity mode, and to obtain model parameters and an effective range of adjacent subarray spacing. Specifically, the relationship between the effective current and the radiation pattern of subarrays with different spatial diversity is determined using the effective current of the antenna and the UCA antenna radiation field formula. The parameters of the UCA antenna circular array and the range of adjacent subarray spacing that meet purity requirements and effective transmission distance are obtained through parameter adjustment.

2. The design method of a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity according to claim 1, characterized in that: The specific steps of establishing the UCA circular array models of different modes in step S1 are as follows: a fixed phase difference is added to each unit in the UCA antenna unit radiation formula in a clockwise order, and then superimposed to form the UCA antenna radiation formulas of different modes. These formulas are then superimposed according to the subarray position relationship and mode combination to obtain the UCA antenna circular array model.

3. The design method of a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity according to claim 1, characterized in that: In step S1, the observation plane is divided specifically as follows: corresponding to the spatial / modal diversity mode of the antenna, it is divided vertically along its propagation direction, each divided area serves as a subset action area of ​​the antenna, and each area works independently to generate a modal vortex wave. During observation, the electric field amplitude and phase parameters of the corresponding area are calculated separately.

4. The design method of a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity according to claim 1, characterized in that: The effective current of the subarray is: Where m represents the mode of the sub-matrix, Represents the support domain of the transformation to the nth unit to the origin, is the vector electric distance representing the radiation field, g m,0,Mod is the expression of the UCA circular array phase factor after Fourier transform of the azimuth angle, j is an imaginary number, θ is the pitch angle, and ρ ′ Mod Represents the radius of the UCA circle array.

5. The design method of a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity according to claim 4, characterized in that: The relationship between the effective current and the radiation pattern of the antenna is: Among them, the integral term represents the vector electric distance, represents a direction vector, is the superposition of the effective current of N units in the mth subarray plus the phase factor, F θ (l) is the far-field directional function of the UCA with mode l, and F θ (l) is:

6. The method for designing a multi-subarray orbital angular momentum antenna with spatial / modal hybrid diversity according to claim 2, wherein: Step S3 specifically involves establishing circular array models of different modes in the simulation software CST, placing them on the same plane, performing parameter sweeps, and finding the parameter combination that produces the highest purity OAM waves within the effective transmission distance in the simulation results. This then determines the optimal circular array parameters and the spacing between adjacent subarrays.

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