Targeted modal vortex wave generation method for time-modulated arrays

Abstract

The application discloses a target mode vortex wave generation method of a time modulation array, and comprises the following steps: constructing a rotationally symmetric time modulation array model; dividing a circular array into P sectors and H rings on average, and distributing unit groups in each ring to form a subarray; each sector is uniformly fed through a group of time modulation circuits; adopting a double-path high-speed radio frequency switch and a pi / 2 fixed phase shifter to construct a quadrature signal time modulation circuit to suppress non-target harmonics; based on a far-field pattern expression of the time modulation array, switch-on time and switch-on time of the switch are designed; by simultaneously feeding different sector antenna units and controlling switch timing of different sectors, a high-purity vortex electromagnetic wave with a mode number of l is generated. The target mode vortex electromagnetic wave generated by the method has the characteristics of high feeding efficiency and high mode purity under the same main lobe gain.

Description

Technical Field

[0001] This invention belongs to the field of array modulation technology, and particularly relates to a novel time modulation array method for generating target mode vortex electromagnetic waves with high energy efficiency. Background Technology

[0002] Time-modulated arrays, as a type of array that achieves beam scanning and radiation characteristic control through time-domain modulation technology, have demonstrated unique advantages in fields such as wireless communication, radar detection, and vortex electromagnetic wave generation. In recent years, with the increasing demands for spectral efficiency and energy utilization in intelligent communication systems, vortex electromagnetic wave generation technology based on time-modulated arrays has become a research hotspot. This technology achieves beam mode control and efficient energy radiation by modulating the time sequence of the excitation signals of the array elements.

[0003] Currently, many scholars have conducted research on the generation of high-quality vortex electromagnetic waves using time-modulated antenna arrays. However, the efficient generation of high-gain, high-energy-efficiency target mode vortex electromagnetic waves still faces many technical challenges, mainly including the following shortcomings: 1) The vortex electromagnetic waves generated by the traditional single-ring circular array structure are limited by the number of array elements, making it difficult to improve the overall system gain; 2) When using a multi-ring fixed-phase excitation method to generate vortex electromagnetic waves, the mode purity is greatly affected; 3) The feed design of traditional time-modulated arrays is highly complex, especially the multi-ring structure, which requires independent control of the feed phase and amplitude of each ring. This not only increases hardware costs but also introduces additional feed losses and harmonic losses due to the complex circuitry. Therefore, it is urgent to propose a new method for generating target mode vortex electromagnetic waves with high energy efficiency using time-modulated arrays. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a novel high-energy-efficiency target mode vortex wave generation method using a time-modulated array. The novel time-modulated array offers greater design freedom, simplifies complex array feed networks, and effectively improves the overall array efficiency through improvements in the time modulation method. The novel time-modulated array features high energy efficiency, high modal purity, and simplified feed network complexity.

[0005] To achieve the above objectives, this invention proposes a method for generating target mode vortex waves using a time-modulated array, comprising: step (1), constructing a rotationally symmetric time-modulated array model: dividing the circular array into P sectors and H sector rings on average,

[0006] The units distributed within each sector ring form a subarray, and each sector is uniformly powered through a set of time modulation circuits.

[0007] Step (2) uses a dual-channel high-speed RF switch and a π / 2 fixed phase shifter to construct an orthogonal signal time modulation circuit to suppress non-target harmonics;

[0008] Step (3), based on the far-field pattern expression of the time-modulated array Design the switch conduction time. And the on-time τ of the switch, where θ is the pitch angle, t represents the azimuth angle, and t represents the moment the switch is turned on.

[0009] Step (4) involves simultaneously feeding different sector antenna elements and controlling the switching timing of different sectors to generate a high-purity vortex electromagnetic wave with a mode number of l.

[0010] Further, in step (1), the specific method for dividing the circular array is as follows: the circular array with radius R is divided into P rotationally symmetric sectors, and the central angle of each sector is θ. Introduce H annexes to divide each sector into H annexes. The units distributed within each annexes form a subarray. Set the total number of array units to Na, the number of units in each sector to Ns = Na / P, and the number of units in the i-th annexes to Ns. i , i = 1, 2, ..., H, and

[0011] By dividing the time modulation array, each cell (i,j) in the array represents the j-th cell distributed within the i-th sector ring, where i = 1, 2, ..., H, j = 1, 2, ..., Ns i In a polar coordinate system with O as the pole and the +x axis as the polar axis, r i,j and ω i,j These are the polar radius and polar angle of element (i,j), respectively. i,j =(r i,j ,ω i,j Let (i,j) be the position vector. In the remaining P-1 sector regions, P-1 rotationally symmetric elements can be obtained by rotating element (i,j), and the corresponding position vectors can be expressed as:

[0012] Different units a in a sector i,j =(r i,j ,ω i,j Together they form a subarray AP1, while the elements of different sectors... They respectively formed rotationally symmetric subarrays AP i i = 1, 2, ..., P, and each sector is uniformly fed through a set of time modulation circuits.

[0013] Further, in step (2), the orthogonal signal time modulation circuit specifically involves setting a programmable gate array and a 0 / π phase shifter in each of the two paths to modulate the input signal, so that the amplitude of the time modulation signal has three states: "1", "0", and "-1". At the same time, two orthogonal signals are generated through a π / 2 phase shifter. and And then combine the two signals:

[0014]

[0015] For time series U p (t) can be decomposed into a Fourier series in the frequency domain:

[0016]

[0017] The time modulation Fourier coefficients of the m-th sideband and the P-th sector are expressed as:

[0018]

[0019] From the above equation, we can see that when m = 0, the quadrature signal time modulation circuit has a suppressive effect on the fundamental wave, and when m = 2KU 3KU 4K-1, K∈Z, the sidebands at the corresponding harmonics are eliminated.

[0020] Furthermore, in step (3), the pattern function is based on the far-field pattern expression of the time-modulated array. for:

[0021]

[0022] In the formula, f0 represents the center frequency of the array element, k is the free space wavenumber, and θ and These are the pitch angle and azimuth angle, respectively, where 0 ≤ θ ≤ π / 2. k = 2π / λ is the wave number in vacuum, and λ is the working wavelength;

[0023] The array factor of a single-sideband time-modulated OAM antenna at the m-th order sideband is expressed as:

[0024]

[0025] To generate vortex electromagnetic waves with mode number l, the array pattern needs to be optimized. The phase factor in the middle satisfies Simultaneously use These represent the normalized switching on times of the two switches, where I and Q represent the two orthogonal signals corresponding to no phase offset and π / 2 phase offset, respectively, and 1n and 2n represent the first and second rising edges of the time-switched modulation waveform in the nth sector, and must satisfy the following:

[0026]

[0027] Calculations show that changing the initial time t of the switch... I 1n To achieve phase modulation of array elements in different sectors, and to generate vortex electromagnetic waves with mode number l, the following conditions must be met:

[0028]

[0029] Where n = 1, 2, ..., P represents the number of different sectors, N = P is the total number of sectors, and l is the topological number of the target mode vortex electromagnetic wave to be generated. and There exists a fixed phase correspondence, therefore when When determined, the timing of the time modulation switch is... That is the only certainty.

[0030] Further, in step (4), the feeding method for different sectors of the antenna array is as follows: the modulated signal is simultaneously transmitted to P orthogonal signal time modulation circuits through a 1-to-P power divider to perform time modulation on the signal respectively. At the same time, for the array units with a total of Ns in each sector, each unit in the sector is connected through a 1-to-Ns power divider, and the synthesized signal U obtained by the time modulation circuit is transmitted to the array. p (t) is fed in as an excitation signal;

[0031] Since signal orthogonality depends on strict timing alignment, it is essential to ensure equal phase distribution during signal distribution by the power divider. Simultaneously, the switching on-cycle should be set, and the phase shifter's operating timing should be controlled within the operating frequency of the programmable logic device.

[0032] Technical effects of the invention:

[0033] This invention discloses a novel high-energy-efficiency target-mode vortex wave generation method for time-modulated arrays. On one hand, by constructing a novel model by dividing a traditional circular array into sector and sector-ring subarrays with rotational symmetry, the overall power supply complexity of the array is significantly reduced. On the other hand, compared with existing schemes that simply use high-speed RF switches for time modulation, this invention utilizes dual high-speed RF switches and π / 2 phase shifters to construct an orthogonal power supply network, which not only suppresses harmonics but also greatly improves the overall array efficiency. Furthermore, the invention provides a corresponding mathematical model and formula derivation for the proposed novel time-modulated array. Simulations demonstrate the generation of vortex electromagnetic waves with higher modal purity at the same gain. Analysis of the overall array efficiency model shows that this method significantly improves the system power supply efficiency and features high energy efficiency, high modal purity, and simplified power supply network complexity. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 This is a diagram of the novel time modulation array structure in this invention;

[0036] Figure 2 This is a circuit diagram of orthogonal signal time modulation in this invention;

[0037] Figure 3 The following is a timing diagram of the switching of the time modulation array of the present invention, wherein (a) is a timing diagram of the switching of the novel time modulation array, and (b), (c), and (d) are the switching timing diagrams of the first, second, and third rings of the circular time modulation array, respectively.

[0038] Figure 4 The following are time modulation signal spectrum diagrams of the present invention, wherein (a), (b), and (c) are time modulation spectrum diagrams of a single switch, switch spectrum diagrams of the novel time modulation circuit, and spectrum comparison diagrams of a single switch and the novel time modulation switch, respectively.

[0039] Figure 5 The near-field intensity map and phase map of the array simulation of the present invention are shown in (a), (b), and (c), respectively, where (a), (b), and (c) are the intensity map and phase map with mode numbers of 1, 2, and 3.

[0040] Figure 6 The diagram shows the far-field electric field cross-section of the array simulation of this invention, where (a), (b), and (c) are electric field cross-sections for mode numbers 1, 2, and 3, respectively.

[0041] Figure 7 The images show a cross-sectional view of the far-field electric field of the array simulation and a comparison of the far-field electric field cross-section of the circular time modulation array of the present invention. Detailed Implementation

[0042] The present application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] The specific implementation steps of the technical solution of this invention are as follows:

[0044] Step 1: Construct a novel time modulation array, following these specific steps:

[0045] Step 1.1, refer to Figure 2 Based on the rotational symmetry structure and subarray partitioning method, the traditional multi-ring antenna array is divided into P rotationally symmetric sector regions, with a circular array aperture of radius R divided into P sector regions, each with a central angle of θ. Introduce H annexes, dividing each sector into H annular regions. The units within each annular region form a subarray. Set the total number of array units to Na, the number of units within each sector region to Ns = Na / P, and the number of units within the i-th annular region to Ns. i , i = 1, 2, ..., H, and

[0046] Step 1.2: Considering the mutual coupling between array elements, based on the existing array division method, the spacing between different sector rings within a sector is between 0.5λ and 0.7λ, and the spacing between different array elements placed within the sector is also maintained between 0.5λ and 0.7λ. In this example, based on the electric field coupling condition, the spacing between array elements is selected as 0.6λ. One array element is placed in the first sector ring, two array elements are placed in the second sector ring, and three array elements are placed in the third sector ring. The sector is then rotated five times to form a novel time modulation array.

[0047] Step 2: Set up the quadrature signal time modulation circuit, and implement it according to the following specific steps:

[0048] Step 2.1, refer to Figure 3 To achieve the cancellation effect of multiple harmonics in two orthogonal signals, a programmable gate array (PLA) and a 0 / π phase shifter are respectively set in these two paths to modulate the input signals, so that the amplitude of the time-modulated signal has three states: "1", "0", and "-1". The bipolar time-modulated rectangular wave signal is generated by simultaneously controlling the state of the switch and the operating state of the 0 / π phase shifter using the PLA.

[0049] Step 2.2: Additionally, by setting a π / 2 phase shifter in the upper half and utilizing the parallel operation mode of programmable logic devices, the 0 / π phase shifters of the I and Q paths are controlled to operate simultaneously, ensuring that the two signals are in an orthogonal state, thus generating two orthogonal signals. and And then combine the two signals:

[0050]

[0051] Step 2.3: For each sector region with a total of Ns array cells, connect each cell in the sector using a 1-to-Ns power divider, and then combine the synthesized signal U. p (t) is fed in as an excitation signal;

[0052] Step 3: Calculate the electric field pattern of the novel time-modulated array, following these specific steps:

[0053] Step 3.1: Assume the center frequency of the array antenna element is f0. Simultaneously, mathematically model the novel time-modulated array based on its partitioning. For each element (i,j) in the array, represent the j-th element distributed within the i-th sector ring, where j = 1, 2, ..., Ns. i Let i = 1, 2, ..., H. In a polar coordinate system with O as the pole and the +x axis as the polar axis, r... i,j and ω i,j These are the polar radius and polar angle of element (i,j), respectively. i,j =(r i,j ,ω i,j If is a position vector, then the corresponding position vector can be expressed as:

[0054] Step 3.2, based on the pattern product theorem and the basic principle of array partitioning in polar coordinates, the corresponding pattern function can be derived as follows:

[0055]

[0056] Step 3.3, for the time series U p (t) can be decomposed into a Fourier series in the frequency domain:

[0057]

[0058] The time modulation Fourier coefficients of the m-th sideband and the P-th sector are expressed as:

[0059]

[0060] Therefore, the array factor of a single-sideband time-modulated OAM antenna at the m-th order sideband can be expressed as:

[0061]

[0062] From the above formula, we can see that m = 2KU 3KU 4K-1, K∈Z, all sidebands are eliminated. It can be seen from the above that the total energy of the input signal is mainly concentrated in the first sideband and the fifth sideband. According to the Fourier expansion formula, the energy of the first sideband is five times that of the fifth sideband, and the energy of other sidebands is even lower, thus achieving the enhancement of fixed sideband energy efficiency.

[0063] Step 4: Set the switching timing according to the target mode vortex electromagnetic wave, and implement it according to the following specific steps:

[0064] Step 4.1: In this example, the array element operating frequency is set to 10GHz, the bandwidth to 800MHz, and the switching conduction period to 600MHz, generating a vortex electromagnetic wave with the target mode l=1. And according to the formula:

[0065]

[0066] Calculate the initial switching time t of the time modulation circuit corresponding to each sector p. I 1n The total number of sectors is P = 6, and p = 1, 2, ..., 6;

[0067] Step 4.2: The vortex electromagnetic wave of the target mode needs to be generated such that the array pattern... The phase factor in the middle satisfies Simultaneously use These represent the normalized switching on times of the switch, respectively, and must satisfy the following conditions:

[0068]

[0069] Through analysis, the turn-on time of the +1 signal switch, where the I-channel and Q-channel signals satisfy the orthogonal cancellation relationship, was calculated respectively. and -1 Signal switch on time and

[0070] Step 5: Perform simulation analysis and system efficiency calculation of the novel time modulation array using CST simulation software, following these specific steps:

[0071] Step 5.1: In the simulation software, model the novel time-modulation array with a total number of array elements Na=36 and the traditional circular ring time-modulation array respectively. Generate an orthogonal time-modulated signal with a center frequency of 10GHz and a switching frequency of 600MHz, as well as the signal modulated by a single switch time, using Matlab. Provide the switching timing diagram and spectrum analysis diagram, and import the modulated signal into the CST simulation software as the excitation for each array element. Perform simulation calculations, view and compare the near-field amplitude and phase distribution and far-field electric field distribution of the novel time-modulation array and the circular ring time-modulation array, and analyze the OMA mode purity.

[0072] Step 5.2, analyze the overall efficiency of the time modulation array:

[0073] η T =η H ·η F

[0074] The harmonic efficiency can be expressed as:

[0075]

[0076] The efficiency of the power supply network can be expressed as:

[0077]

[0078] The power supply network efficiency in this design is set to 1. The main focus is on analyzing and comparing the suppression of multiple harmonics by the novel time modulation array and its impact on the harmonic efficiency of the system array.

[0079] The effectiveness of this invention can be further illustrated by the following simulation results:

[0080] 1. Simulation experimental environment of this invention:

[0081] CST Studio Suite 2024, MATLAB R2023b, CPU: R9-7940, GPU: NVIDA RTX-4060, WINDOWS11.

[0082] 2. Simulation conditions:

[0083] The total number of array elements is 36. Based on the electric field coupling condition, the spacing between array elements is selected as 0.6λ. One array element is placed in the first sector ring, two array elements are placed in the second sector ring, and three array elements are placed in the third sector ring. The sectors are rotated 5 times to form a new time modulation array. In this example, the array element operating frequency is set to 10GHz, the bandwidth is 800MHz, the switching frequency is set to 600MHz, and the single switching time is 20.833 nanoseconds, generating vortex electromagnetic waves with target mode l=1.

[0084] 3. Simulation results:

[0085] Figure 1 A novel method for partitioning time-modulated arrays is presented, which divides a circular array into P sectors and H sector rings. Based on rotational symmetry, the sectors are rotated to obtain the complete array distribution.

[0086] Figure 2 The design of the time modulation switch circuit is given. The time modulation circuit of each sector consists of a programmable logic device, two 0 / π phase shifters, a π / 2 fixed phase shifter, and two high-speed RF switches. The switching turn-on timing is designed by programming to generate a fixed target mode vortex electromagnetic wave.

[0087] Figure 3Four sets of switch turn-on timing diagrams are given. (a) shows the turn-on timing diagram of the novel time-modulated switch, including I and Q signals from six sectors. Black indicates the turn-on time when the switch is at phase 0, and gray indicates the turn-on time when the switch is at phase π. It is important to note that the output is positive when the switch is at phase 0 and negative when it is at phase π, thus achieving bipolar output. (b), (c), and (d) show the switch turn-on timing diagrams of traditional circular time-modulated arrays, requiring 6, 12, and 18 sets of programmable logic devices and high-speed RF switches, respectively. In contrast, the number of programmable logic devices and high-speed RF switches used in this invention is reduced to 1 / 6 of that in traditional circular arrays, simplifying the circuit power supply. To meet the generation requirements of the target mode l=1 vortex electromagnetic wave of the novel time-modulated array, the switch timing... The calculation is performed, where N represents the total number of sectors in the sector-based partitioning method, and n represents each sector. When N = 6, n = 1, 2, ..., 6, the number of modes l = 1, and the fixed-time correspondence is satisfied. The on-time of the novel time-modulated array switch can be obtained as shown in Table 1; for the on-time of the circular time-modulated array switch... Where N i n represents the total number of units in each annulus. i Let i represent each unit in each ring, i = 1, 2, 3. When the mode number l = 1, and the ring 1 has N1 = 6, n1 = 1, 2, ..., 6; the ring 2 has N2 = 12, n2 = 1, 2, ..., 12; and the ring 3 has N3 = 18, n3 = 1, 2, ..., 18, the on-time of the ring time modulation array switches can be obtained as shown in Table 2.

[0088] Table 1: Switching Timing of the Novel Time Modulation Array

[0089]

[0090] Table 2: Switching Timing of Circular Time Modulation Array

[0091] <![CDATA[Feeding unit Ns i > Ring 1 Ring 2 Ring 3 1 0.083 0.042 0.028 2 0.917 0.958 0.972 3 0.750 0.875 0.917 4 0.583 0.792 0.861 5 0.417 0.708 0.806 6 0.250 0.625 0.750 7 - 0.542 0.694 8 - 0.458 0.639 9 - 0.375 0.583 10 - 0.292 0.528 11 - 0.208 0.472 12 - 0.125 0.417 13 - - 0.361 14 - - 0.306 15 - - 0.250 16 - - 0.194 17 - - 0.139 18 - - 0.083

[0092] To meet the requirements for generating target mode vortex electromagnetic waves in a novel time-modulated array, the switching timing... The calculation is performed where N = 6, l = 1, n = 1, 2, ..., 6, and a fixed time correspondence is satisfied. A novel time-modulated array switching timing sequence can be obtained.

[0093] Figure 4Time modulation spectrum diagrams are given. (a) shows the time modulation spectrum of a single switch, (b) shows the spectrum of bipolar quadrature time modulation, and a comparison between the two is shown in (c). The bipolar quadrature time modulation circuit can significantly suppress the distribution of energy in other spectra, making the energy more concentrated. By using the first frequency band as the target modulation band, the harmonic efficiency of the single-switch time modulation circuit can be calculated to be 19.89%, while the harmonic efficiency of the bipolar quadrature time modulation circuit is 52.11%, resulting in a total harmonic efficiency improvement of 32.22%.

[0094] Figure 5 The near-field intensity distribution and OAM mode spectrum of vortex electromagnetic waves generated by a novel time-modulated array, calculated using CST simulation software, are presented. (a), (b), and (c) represent vortex waves in modes l=1, l=2, and l=3, respectively. Calculations show that the modal purities for l=1, l=2, and l=3 are 97.6%, 94.3%, and 88.4%, respectively. Compared to the circular time-modulated array, this novel time-modulated array can generate vortex electromagnetic waves with higher modal purity.

[0095] Figure 6 Cross-sectional views of the far-field radiation pattern of vortex electromagnetic waves generated by a novel time-modulated array, calculated by CST simulation software, are given, where (a), (b), and (c) are vortex waves of modes l=1, l=2, and l=3, respectively.

[0096] Figure 7 A comparison of the far-field radiation patterns of the novel time-modulated array and the circular time-modulated array calculated using CST simulation software is presented. The results show that the novel time-modulated array has better sidelobe suppression than the circular time-modulated array.

[0097] In summary, the novel time-modulation array can generate target mode vortex electromagnetic waves with higher energy efficiency and lower sidelobe levels by controlling the timing of high-speed RF switches, significantly reducing the overall power supply complexity of the array and improving the system power supply efficiency.

Claims

1. A method for generating target mode vortex waves using a time-modulated array, characterized in that: include, Step (1), construct a rotationally symmetric time modulation array model: divide the circular array into P sectors and H sector rings on average. The units distributed in each sector ring form a subarray. Each sector is uniformly fed through a set of time modulation circuits. Step (2) uses a dual-channel high-speed RF switch and a π / 2 fixed phase shifter to construct an orthogonal signal time modulation circuit to suppress non-target harmonics; Step (3), based on the far-field pattern expression of the time-modulated array Design the switch conduction time. And the on-time τ of the switch, where θ is the pitch angle, t represents the azimuth angle, and t represents the moment the switch is turned on. Step (4) involves simultaneously feeding different sector antenna elements and controlling the switching timing of different sectors to generate a high-purity vortex electromagnetic wave with a mode number of l. In step (1), the specific method for dividing the circular array is as follows: the circular array with radius R is divided into P rotationally symmetric sectors, and the central angle of each sector is θ. Introduce H annexes to divide each sector into H annexes. The units distributed within each annexes form a subarray. Set the total number of array units to Na, the number of units in each sector to Ns = Na / P, and the number of units in the i-th annexes to Ns. i , i = 1, 2, ..., H, and By dividing the time modulation array, each cell (i,j) in the array represents the j-th cell distributed within the i-th sector ring, where i = 1, 2, ..., H, j = 1, 2, ..., Ns i In a polar coordinate system with O as the pole and the +x axis as the polar axis, r i,j and ω i,j These are the polar radius and polar angle of element (i,j), respectively. i,j =(r i,j ,ω i,j Let (i,j) be the position vector. In the remaining P-1 sector regions, P-1 rotationally symmetric elements can be obtained by rotating element (i,j), and the corresponding position vectors can be expressed as: Different units a in a sector i,j =(r i,j ,ω i,j Together they form a subarray AP1, while the elements of different sectors... They respectively formed rotationally symmetric subarrays AP i , i = 1, 2, ..., P, and each sector is uniformly fed through a set of time modulation circuits; In step (2), the quadrature signal time modulation circuit specifically involves setting a programmable gate array and a 0 / π phase shifter in each of the two paths to modulate the input signal, so that the amplitude of the time modulation signal has three states: "1", "0", and "-1". At the same time, a π / 2 phase shifter generates two orthogonal signals. and And then combine the two signals: For time series U p (t) can be decomposed into a Fourier series in the frequency domain: The time modulation Fourier coefficients of the m-th sideband and the P-th sector are expressed as: From the above formula, we can see that when m = 0, the quadrature signal time modulation circuit has a suppressive effect on the fundamental wave, and when m = 2KU 3K U 4K-1, K∈Z, the sidebands at the corresponding harmonics are eliminated. In step (3), the pattern function is based on the far-field pattern expression of the time-modulated array. for: In the formula, f0 represents the center frequency of the array element, k is the free space wavenumber, and θ and These are the pitch angle and azimuth angle, respectively, where 0 ≤ θ ≤ π / 2. k = 2π / λ is the wave number in vacuum, and λ is the working wavelength; The array factor of a single-sideband time-modulated OAM antenna at the m-th order sideband is expressed as: To generate vortex electromagnetic waves with mode number l, the array pattern needs to be optimized. The phase factor in the middle satisfies Simultaneously use These represent the normalized switching on times of the two switches, where I and Q represent the two orthogonal signals corresponding to no phase offset and π / 2 phase offset, respectively, and 1n and 2n represent the first and second rising edges of the time-switched modulation waveform in the nth sector, and must satisfy the following: Calculations show that changing the initial time t of the switch... I 1n To achieve phase modulation of array elements in different sectors, and to generate vortex electromagnetic waves with mode number l, the following conditions must be met: Where n = 1, 2, ..., P represents the number of different sectors, N = P is the total number of sectors, and l is the topological number of the target mode vortex electromagnetic wave to be generated. and There exists a fixed phase correspondence, therefore when When determined, the timing of the time modulation switch is... That is the only certainty.

2. The method for generating target mode vortex waves using a time-modulated array as described in claim 1, characterized in that: In step (4), the feeding method for different sectors of the antenna array is as follows: the modulated signal is simultaneously transmitted to P orthogonal signal time modulation circuits through a 1-to-P power divider to perform time modulation on the signal respectively. At the same time, for the array elements with a total number of Ns in each sector, each element in the sector is connected through a 1-to-Ns power divider, and the synthesized signal U obtained by the time modulation circuit is transmitted to the array. p (t) is fed in as an excitation signal; Since signal orthogonality depends on strict timing alignment, it is necessary to ensure that the power divider distributes signals in equal phase, and at the same time set the switching on period to control the phase shifter's operating time within the operating frequency of the programmable logic device.

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