Vortex electromagnetic wave generation method based on circular array antenna

Abstract

The invention provides a vortex electromagnetic wave generation method based on a circular ring array antenna, and the method comprises the steps: enabling a plurality of array elements of the circular ring array antenna to be distributed on a circumference in a uniform circular ring manner, and enabling the amplitude of a signal loaded on each array element to be the same; and performing equal-amplitude different-phase feeding on each array element to obtain a multi-mode vortex electromagnetic wave. According to the vortex electromagnetic wave generating method and the vortex electromagnetic wave generating device, the multi-modal vortex electromagnetic wave is obtained by performing equal-amplitude and different-phase feeding on each array element of the ring array antenna, so that the multi-modal vortex electromagnetic wave is generated based on the ring array antenna, and the problems of beam divergence and modal purity reduction of the vortex wave in a high modal are avoided.

Description

Technical Field

[0001] The present disclosure relates to the field of microwave technology, and in particular to a method for generating vortex electromagnetic waves based on a circular ring array antenna. Background Art

[0002] With the continuous increase in wireless users, it is becoming increasingly challenging to meet the growing capacity demand in wireless networks. In order to meet this demand under limited resources, new technologies must be relied upon to improve system capacity and spectrum utilization. In the past decade, electromagnetic waves carrying orbital angular momentum (OAM), namely vortex electromagnetic waves, have attracted much attention due to their high spectrum efficiency and anti-interference ability. Therefore, this technology will inevitably bring new possibilities to wireless communications. Vortex electromagnetic waves have typical phase and amplitude characteristics compared to plane electromagnetic waves. It presents an equiphase surface of vortex shape, the phase shows periodic changes on the same cross section, and has a vortex phase distribution. The vortex mode order carried by vortex electromagnetic waves, namely the orbital angular momentum topological core, theoretically has infinite modes. At the same time, it is mathematically proved that the modes are mutually orthogonal due to the vortex phase characteristics. The amplitude and phase characteristics of vortex electromagnetic waves are completely different from those of plane waves, and plane waves can be regarded as a special case of vortex electromagnetic waves.

[0003] In recent years, with the increase in communication rate requirements and the increasing shortage of spectrum resources, people are in urgent need of adopting new technologies to improve the capacity of wireless communication channels. Vortex beams carrying orbital angular momentum have become the focus of communication research by significantly improving channel capacity through modal multiplexing. The rotation factors carried by electromagnetic vortex waves form a spiral phase plane along the transmission axis, which makes the beams of different modal values ​​orthogonal, and can realize multi-channel information transmission in the same frequency band, ensuring the independence of channels. However, electromagnetic vortex beam communication still faces multiple challenges, including the limitation of beam divergence on long-distance information transmission, the sidelobe interference in multi-beam scenarios may affect the integrity of modal information, resulting in a decrease in modal purity, and the uncontrollability of beam radiation direction. Summary of the invention

[0004] The technical problem to be solved by the present disclosure is to overcome the defects of the prior art that vortex waves will have beam divergence in high modes and the modal purity is reduced, and a method for generating vortex electromagnetic waves based on a circular array antenna is provided.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The first aspect of the present disclosure provides a method for generating vortex electromagnetic waves based on a circular ring array antenna, the generating method comprising:

[0007] Distributing the plurality of array elements of the circular array antenna on the circumference in the form of uniform circular rings, and the signal amplitude loaded on each array element is the same;

[0008] Each array element is fed with equal amplitude and phase difference to obtain a multi-mode vortex electromagnetic wave.

[0009] Preferably, the generating method further comprises:

[0010] Set the preset value of the phase difference of the loading signal between adjacent array elements.

[0011] Preferably, the generating method further comprises:

[0012] Arrange multiple array elements with the same structure at preset intervals to obtain an array.

[0013] Preferably, the circular array antenna includes a microstrip patch antenna and a horn antenna.

[0014] Preferably, the array element comprises at least one of a radiation patch, a coaxial cable, a dielectric substrate, a coaxial feeding port and a reference ground.

[0015] Preferably, the coaxial feeding port coincides with the center of the coaxial cable.

[0016] Preferably, the reference ground has the same size as that of the dielectric substrate.

[0017] Preferably, the generating method further comprises:

[0018] Simulating the circular array antenna to obtain an electric field amplitude diagram and a gain diagram;

[0019] Based on the electric field amplitude diagram and the gain diagram, a vortex electromagnetic wave carrying orbital angular momentum is obtained.

[0020] Preferably, the generating method further comprises:

[0021] The simulation results of circular array antennas of different sizes are compared to obtain comparative results.

[0022] Preferably, the radius of the circular array antenna is negatively correlated with the cavity of the vortex electromagnetic wave.

[0023] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0024] The positive and progressive effects of this disclosure are:

[0025] The present invention obtains multi-modal vortex electromagnetic waves by feeding each array element of the circular array antenna with equal amplitude and differential phase, thereby realizing the generation of multi-modal vortex electromagnetic waves based on the circular array antenna and avoiding the problem of beam divergence of vortex waves in high modes and reduced modal purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flowchart of a method for generating vortex electromagnetic waves based on a circular array antenna is provided as an exemplary embodiment of the present disclosure.

[0027] Figure 2 A schematic structural diagram of a circular array antenna design model provided for an exemplary embodiment of the present disclosure.

[0028] Figure 3 A phase diagram of a feeding network of a circular array antenna provided by an exemplary embodiment of the present disclosure.

[0029] FIG4( a ) is a schematic diagram of the back side of an array element structure of a patch circular array antenna with a center frequency of 31 GHz provided by an exemplary embodiment of the present disclosure.

[0030] FIG4( b ) is a side schematic diagram of an array element structure of a patch circular array antenna with a center frequency of 31 GHz provided by an exemplary embodiment of the present disclosure.

[0031] FIG5( a ) is a structural diagram of a 36-element multi-mode circular array antenna provided by an exemplary embodiment of the present disclosure.

[0032] FIG5( b ) is a diagram of the S11 structure of a 36-element multi-mode circular array antenna according to an exemplary embodiment of the present disclosure.

[0033] Figure 6 The EH plane gain pattern of a 36-element multi-mode array antenna provided by an exemplary embodiment of the present disclosure.

[0034] Figure 7 An electric field phase diagram of a 36-element multi-mode circular array antenna provided as an exemplary embodiment of the present disclosure.

[0035] Figure 8 An electric field amplitude diagram of a 36-element multi-mode circular array antenna provided as an exemplary embodiment of the present disclosure.

[0036] Fig. 9 An electric field amplitude diagram of a 36-element multi-mode circular array antenna as the circular radius changes, provided as an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.

[0038] Prefixes such as "first" and "second" are used in the embodiments of the present disclosure only to distinguish different description objects, and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of prefixes such as ordinal numbers to distinguish description objects in the embodiments of the present disclosure does not constitute a limitation on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and no unnecessary limitation should be constituted due to the use of such prefixes. In addition, in the description of the present embodiment, unless otherwise specified, the meaning of "plurality" is two or more.

[0039] In the embodiments of the present disclosure, the collection, storage, use, processing, transmission, provision and disclosure of user personal information involved are in compliance with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0040] Figure 1 A flow chart of a method for generating vortex electromagnetic waves based on a circular array antenna is provided as an exemplary embodiment of the present disclosure, such as Figure 1 As shown, the generation method includes:

[0041] S1. Distribute multiple array elements of the circular array antenna on the circumference in the form of uniform circular rings, and the signal amplitude loaded on each array element is the same;

[0042] In this embodiment, the circular ring array antenna is usually a uniform circular ring array antenna.

[0043] S2. Feed each array element with equal amplitude and phase difference to obtain multi-mode vortex electromagnetic waves.

[0044] This embodiment designs a multi-mode OAM array antenna composed of 36 microstrip patch array elements, wherein the number of array elements of the circular array antenna is 36, and the 36 array elements are arranged in the form of uniform circular rings, which is a more compact arrangement.

[0045] In this embodiment, the mode number of the vortex electromagnetic wave can reach up to 32 modes (ie, there are 16 positive modes and 16 corresponding negative modes), which can functionally achieve 32 different vortex wave modes.

[0046] It should be noted that the execution order of the above S1 and S2 can be adjusted according to actual conditions.

[0047] In the specific implementation process, as described in classical electromagnetic theory, the characteristics of electromagnetic radiation are: the transmitted beam carries both energy and momentum, and momentum can be divided into two parts: linear momentum and angular momentum. It is conserved and can be divided into spin angular momentum (SAM) and orbital angular momentum, which are expressed as and The relationship between them can be expressed as: Angular momentum Spin angular momentum and orbital angular momentum The expressions are as shown in formula (1), formula (2) and formula (3):

[0048]

[0049] Among them, E represents the electric field intensity, B represents the magnetic induction intensity, A represents the vector potential function, r represents the position vector, ε0 represents the dielectric constant in vacuum, * represents the Hermitian conjugation, and j represents the imaginary unit. Different from the spin characteristics of SAM, it carries the OAM phase factor The beam is manifested as an external spatial distribution feature, and theoretically the modal value l can take any order, with an infinite spiral distribution form. The vortex beam can be expressed as shown in formula (4):

[0050]

[0051] in, Represents the amplitude of the electromagnetic wave, θ, Represent the pitch angle and azimuth angle respectively. For the case of mode l = 0, the electromagnetic wave expression loses its The changing phase is what is usually called a plane wave form. For the modal value l≠0, the beam has a wavefront phase with a spiral periodic distribution, the number of periods is equal to the absolute value of the modal |l|, and a field distribution morphology with a central depression appears, and the divergence of the high-order OAM beam is more severe, as shown in formula (5):

[0052]

[0053] The modal multiplexing of OAM comes from the orthogonality between its channels. Substituting the OAM signals of mode l1≠l2 into formula (5), we can get formula (6):

[0054]

[0055] According to the above formula analysis results, it can be deduced that the channels between different orbital angular momentum modes l1 and l2 are independent, which means that multiple signals carrying OAM can be transmitted simultaneously in the same frequency band without mutual interference. In theory, there is no limit to the number of modal orders, which makes OAM have unlimited carrying capacity and multiplexing flexibility in the field of wireless communications.

[0056] In this embodiment, uniform circular patch array antennas of different sizes are designed to analyze the performance of vortex electromagnetic waves, and 32 modes of vortex electromagnetic waves are realized under different excitation conditions. Specifically, multi-mode vortex electromagnetic waves are obtained by feeding each array element of the circular array antenna with equal amplitude and differential phase, thereby realizing the generation of multi-mode vortex electromagnetic waves based on the circular array antenna, avoiding the problem of beam divergence and decreased modal purity of vortex waves in high modes.

[0057] In an optional embodiment, the generating method further includes:

[0058] Arrange multiple array elements with the same structure at preset intervals to obtain an array.

[0059] In this embodiment, in the design of using a uniform circular array (UCA) to realize a vortex electromagnetic wave, as shown in FIG. Figure 2 As shown, by feeding each array element in the uniform circular array antenna with equal amplitude difference phase, an electromagnetic wave with spiral phase wavefront characteristics is obtained. To obtain a vortex beam using UCA, the array elements must be evenly distributed around the circle, and the amplitude of the signal loaded on each array element must remain the same. The phase of the loaded signal between adjacent array elements needs to differ by a preset value Δφ=2πl / N, where N represents the number of array elements.

[0060] In an optional embodiment, the generating method further includes:

[0061] Arrange multiple array elements with the same structure at preset intervals to obtain an array.

[0062] In this embodiment, Figure 3 is the phase diagram of the feeding network of the circular array antenna, and the eight array elements with the same structure are arranged at the same interval. When the unit antennas in the circular phased array are fed with equal amplitude and there is an equal phase difference between adjacent array elements, the array antenna will generate OAM vortex electromagnetic waves of different modes. Assume Figure 3 The initial phase θ of the first unit antenna feeding is 0, then the second unit antenna feeding phase is θ±Δφ, the third unit antenna feeding phase is θ±2Δφ, and so on. The excitation phase difference of each adjacent patch feeding is an integer multiple of . For an array antenna with n unit antennas, the total phase difference Δφ generated by feeding one circle is 2πl / n, where l represents the OAM mode. Therefore, different feeding phase differences Δφ will generate different OAM mode values ​​l.

[0063] In an optional embodiment, the circular array antenna includes a microstrip patch antenna and a horn antenna.

[0064] This embodiment designs a circular array antenna using microstrip patch antennas and horn antennas as units.

[0065] In an optional embodiment, the array element includes at least one of a radiation patch, a coaxial cable, a dielectric substrate, a coaxial feeding port, and a reference ground.

[0066] In an optional embodiment, the coaxial feeding port coincides with the center of the coaxial cable.

[0067] In an optional embodiment, the reference ground is the same size as the dielectric substrate.

[0068] In the specific implementation process, for example, this embodiment proposes a Ka-band (center frequency is 31 GHz) 36-element multi-mode OAM microstrip array antenna with coaxial feeding (back feeding), and its element structure and size information are shown in Figure 4 (a) (back), Figure 4 (b) (side) and Table 1, and the size unit is mm.

[0069] The structure of the array element from top to bottom is: radiation patch, coaxial cable, dielectric substrate, coaxial feed port and reference ground. Wt represents the width of the patch, and Ls represents the length of the patch. Rin represents the radius of the coaxial cable, and H represents the height of the dielectric substrate and the coaxial cable. Ws represents the width of the dielectric substrate, Ls represents the length of the dielectric substrate, Rout represents the radius of the coaxial feed port, and d1 represents the distance from the coordinate point to the center of the circle.

[0070] It should be noted that the material of the dielectric substrate may be Rogers RO3003, the coaxial feeding port coincides with the center of the coaxial cable, the reference ground and the dielectric substrate are consistent in size, and the impedance of the coaxial cable is set to 50 ohms.

[0071] Table 1

[0072]

[0073] In an optional embodiment, the generating method further includes:

[0074] Simulate the circular array antenna to obtain the electric field radiation diagram and gain diagram;

[0075] Based on the electric field amplitude diagram and gain diagram, the vortex electromagnetic wave carrying orbital angular momentum is obtained.

[0076] In order to obtain vortex waves, 36 identical array elements need to be arranged around the origin of the coordinate system at intervals of 10° to form an array. At the same time, the size of the dielectric substrate is enlarged. The corresponding array element parameters are obtained through continuous optimization. Finally, the side length of the dielectric substrate is 70 mm, and the distance between the center of the array element and the center of the circle, i.e., the radius, is 30 mm. Figure 5(a) and 5(b)As shown, Figure 5(a) is the structure diagram of the 36-element multi-mode UCA; Figure 5(b) is the S11 of the 36-element multi-mode UCA; the structure of the Ka-band 36-element multi-mode array antenna. After simulation optimization, check the performance parameters of this array antenna.

[0077] By checking the S parameters of the multi-mode 36-element array in the Ka band, it can be seen that at the 31 GHz frequency, its S11 is -23.72 dB (<-20 dB).

[0078] Modal characteristics analysis, such as Figure 6 is the EH plane gain pattern of the 36-element multi-mode array antenna (for example, Figure 6 (the gain directional diagrams are l=0, l=1, l=4, l=8, l=12, and l=16), when l=0, the gain is concentrated in the main lobe, the center gain is the strongest and the surrounding gains gradually decay; when l=1, the main lobe disappears, and many smaller side lobes appear, the center gain decreases and the side lobe gain is enhanced; when l=4, an area with lower gain than the surrounding area appears in the center of the 3D gain diagram, and a central hole problem occurs. The main lobe gain is significantly lower than the side lobe gain, and the lobe width becomes larger, resulting in weakened directivity; as l increases, the main lobe gain decreases, the number of side lobes increases and their gain gradually increases, the lobe widens and the directivity weakens, and the center gain is lower than the surrounding gain.

[0079] Observe the electric field phase diagram of the 36-element multi-mode array antenna, as shown in Figure 7 As shown (for example, Figure 7 The electric field phase diagram for l = 0, l = 1, l = 4, l = 8, l = 12, and l = 16 shows that the change in phase is related to the mode number, which is specifically manifested as the number of highlighted spiral arms in the figure is the same as the corresponding mode number. It can be seen from the phase diagram that as the mode number increases, irregular phase gradient changes appear in the middle of the image. This is the central void phenomenon, which is more obvious in the electric field amplitude diagram.

[0080] In this embodiment, Figure 8 For this purpose, the electric field amplitude diagram of the Ka-band 36-element multi-mode circular array antenna (for example, Figure 8(The electric field amplitude diagram of 36-element multi-mode UCA with l=0, l=1, l=4, l=8, l=12, and l=16). When l=0, the electric field energy at the center of the circular array antenna is the strongest and the peripheral energy gradually decays. Because the phase increment is zero degrees at this time, the phase structure of the generated electromagnetic wave beam has not changed and is a plane wave, so the electric field energy of its electric field radian diagram will not be distributed in a "vortex shape". When l=1, the phase structure of the beam at this time changes to generate an OAM vortex electromagnetic wave, and its electric field energy rotates and diffuses to the surroundings. When l=4, its electric field energy is obviously distributed in a "vortex shape" and the outward diffusion is more serious, and a small area with very weak field strength appears in the center. As the number of modes increases, this change becomes more and more significant.

[0081] In an optional embodiment, the generating method further includes:

[0082] The simulation results of circular array antennas of different sizes are compared to obtain comparative results.

[0083] In an optional embodiment, the radius of the circular array antenna is negatively correlated with the cavity of the vortex electromagnetic wave.

[0084] In this embodiment, the structural characteristics are analyzed. Fig. 9 The electric field amplitude diagram of the 36-element multi-mode circular array antenna as the circular radius changes (for example, Fig. 9 The electric field amplitude comparison diagram of different modes (l = 0, l = 1, l = 8, l = 16) with different array radius sizes is shown in Figure 1. The parameters of the three arrays are array a: Ls = 70mm, Ws = 70mm, Rad = 30mm; array b: Ls = 100mm, Ws = 100mm, Rad = 40mm; array c: Ls = 110mm, Ws = 110mm, Rad = 50mm. Each antenna array has 32 modes. For the convenience of observation, the modes l = 0, l = 1, l = 8, and l = 16 are taken for comparison.

[0085] from Fig. 9 It can be clearly seen that as the size of the array antenna changes, the electric field diagram of the antenna array will also change to a certain extent. When the radius of the circular array antenna increases, it can be seen from the electric field amplitude diagram that the electric field intensity at the edge decreases and the electric field at the center increases. Fig. 9 It is manifested as the reduction of the central cavity of the vortex electromagnetic wave, and the effect is more obvious when the vortex wave mode is higher.

[0086] This embodiment designs a circular array antenna with microstrip patch antennas and horn antennas as units, and designs a vortex electromagnetic wave microstrip array antenna in combination with three-dimensional electromagnetic wave simulation software. The simulation results of the electric field radian diagram and the gain diagram show that the designed vortex electromagnetic wave microstrip array antenna can effectively generate vortex electromagnetic waves with orbital angular momentum characteristics. In addition, this embodiment also analyzes and compares the simulation results of circular array antennas of different sizes, and the central void phenomenon of the vortex electromagnetic wave is improved under different structures.

[0087] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. A method for generating vortex electromagnetic waves based on a circular array antenna, characterized in that: The generation method comprises: Distributing the plurality of array elements of the circular array antenna on the circumference in the form of uniform circular rings, and the signal amplitude loaded on each array element is the same; Each array element is fed with equal amplitude and phase difference to obtain a multi-mode vortex electromagnetic wave.

2. The method for generating vortex electromagnetic waves based on a circular ring array antenna as claimed in claim 1, characterized in that: The generating method further comprises: Set the preset value of the phase difference of the loading signal between adjacent array elements.

3. The method for generating vortex electromagnetic waves based on a circular ring array antenna as claimed in claim 1, characterized in that: The generating method further comprises: Arrange multiple array elements with the same structure at preset intervals to obtain an array.

4. The method for generating vortex electromagnetic waves based on a circular ring array antenna as claimed in claim 1, characterized in that: The circular array antenna includes a microstrip patch antenna and a horn antenna.

5. The method for generating vortex electromagnetic waves based on a circular ring array antenna as claimed in claim 1, characterized in that: The array element includes at least one of a radiation patch, a coaxial cable, a dielectric substrate, a coaxial feeding port and a reference ground.

6. The method for generating vortex electromagnetic waves based on a circular ring array antenna as claimed in claim 5, characterized in that: The coaxial feeding port coincides with the center of the coaxial cable.

7. The method for generating vortex electromagnetic waves based on a circular ring array antenna as claimed in claim 5, characterized in that: The reference ground has the same size as that of the dielectric substrate.

8. The method for generating vortex electromagnetic waves based on a circular ring array antenna according to claim 1, characterized in that: The generating method further comprises: Simulating the circular array antenna to obtain an electric field amplitude diagram and a gain diagram; Based on the electric field amplitude diagram and the gain diagram, a vortex electromagnetic wave carrying orbital angular momentum is obtained.

9. The method for generating vortex electromagnetic waves based on a circular ring array antenna according to claim 1, characterized in that: The generating method further comprises: The simulation results of circular array antennas of different sizes are compared to obtain comparative results.

10. The method for generating vortex electromagnetic waves based on circular ring array antenna according to claim 1, characterized in that: The radius of the circular array antenna is negatively correlated with the cavity of the vortex electromagnetic wave.

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