Three-degree-of-freedom circular array vortex beam generation method

Abstract

The application relates to a three-freedom-degree circular array vortex beam generation method, which comprises the following steps: step 1, designing a left-handed circular polarization unit and a right-handed circular polarization circular ring unit for generating a three-freedom-degree vortex beam; step 2, designing a left-handed circular polarization vortex beam circular array and a right-handed circular polarization vortex beam circular array based on the left-handed circular polarization unit and the right-handed circular polarization circular ring unit respectively; and step 3, generating a three-freedom-degree circular array vortex beam based on the left-handed circular polarization vortex beam circular array and the right-handed circular polarization vortex beam circular array. The application firstly proposes three degrees of freedom of circular array radiation field regulation, namely, array element polarization, array element arrangement mode and excitation phase mode; secondly, the three degrees of freedom are combined and analyzed, and a multi-freedom-degree circular array vortex beam generation method based on any combination of the three degrees of freedom is obtained through theoretical derivation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circular array vortex beam synthesis, and particularly relates to a three-degree-of-freedom circular array vortex beam generation method. BACKGROUND

[0002] At present, due to the limitation of spectrum and polarization resources, there is a higher requirement for increasing spectrum resources and improving spectrum utilization. Therefore, the vortex beam with a spiral phase and carrying orbital angular momentum (OAM) has attracted extensive attention of researchers. The OAM beam has a spiral phase wave front and an infinite number of modal values, and the modal values are orthogonal to each other and do not interfere with each other, so that a plurality of different vortex beams can be transmitted at the same frequency, and theoretically an infinite number of channels can be constructed in the same space.

[0003] Based on the above reasons, the vortex beam has a wide application in improving the channel capacity and spectrum utilization of a wireless communication system, and can provide a new degree of freedom for beam control. In a microstrip array, a common vortex beam generation method is to uniformly arrange the same units along the circumference in the same direction to form a circular array. In the uniform circular array, there are a plurality of degrees of freedom, such as linear polarization or circular polarization of the array element, same direction or self-rotating arrangement of the array element, and same phase distribution or gradient phase distribution of the excitation phase. These degrees of freedom will affect the finally generated beam, and the beams generated by the cross combination of the degrees of freedom are also quite different. SUMMARY

[0004] The present application provides a three-degree-of-freedom circular array vortex beam generation method, characterized in that the three-degree-of-freedom circular array vortex beam generation method comprises the following steps:

[0005] Step 1, designing left-handed circular polarization elements and right-handed circular polarization circular elements for generating three-degree-of-freedom vortex beams;

[0006] Step 2, designing left-handed circular polarization vortex beam circular arrays and right-handed circular polarization vortex beam circular arrays based on the left-handed circular polarization elements and the right-handed circular polarization circular elements, respectively;

[0007] Step 3, generating three-degree-of-freedom circular array vortex beams based on the left-handed circular polarization vortex beam circular arrays and the right-handed circular polarization vortex beam circular arrays;

[0008] When the array element polarization is left-handed circular polarization, if the rotation angle mode number l1≠0 in the left-handed circular polarization vortex beam circular array and the excitation phase mode number l2≠0 in the left-handed circular polarization vortex beam circular array, the array can generate a left-handed circular polarization vortex beam with a mode number of l2-l1;

[0009] When the array element is right-handed circularly polarized, if the number of rotation angle modes in the right-handed circularly polarized vortex beam circular array l1'≠0 and the number of excitation phase modes in the right-handed circularly polarized vortex beam circular array l2'≠0, the array can generate a right-handed circularly polarized vortex beam with a mode number of l1'+l2'.

[0010] Further, in step 1, the left-handed circularly polarized element and the right-handed circularly polarized circular ring element are both rectangular patches with oblique diagonal slots, and the diagonal slot directions of the two elements are orthogonal.

[0011] The left-handed circularly polarized element and the right-handed circularly polarized circular ring element are both composed of F4B dielectric plates, and the dielectric constant is ε r =2.65, the electric tangent loss is tanδ=0.001, the length, width and height of the dielectric plate of the left-handed circularly polarized element are g a , g b , h1 respectively; the length, width and height of the dielectric plate of the right-handed circularly polarized element are g a , g b , h2 respectively; the radii of the circular rings in which the two elements are distributed are r1 and r2 respectively; the metal structure material is copper, the conductivity is σ=5.8×107S / m, and the thickness is 0.018mm; the length and width of the rectangular radiation patch of the left-handed circularly polarized element are a1 and b1 respectively, the corresponding oblique diagonal slot length and width are L1+L2, the width is w1, the oblique angle is j1, and the corresponding feed line width is w2; the length and width of the rectangular radiation patch of the right-handed circularly polarized element are a2 and b2 respectively, the corresponding oblique diagonal slot length and width are L3+L4, the width is w4, the oblique angle is j2, and the corresponding feed line width is w5.

[0012] Further, in step 1, the edge length of the radiation patch is obtained according to the open microstrip line edge expansion length ΔL analysis formula and the rectangular patch antenna resonance formula:

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] In the formula, ΔL is the edge expansion length of the microstrip line, h is the thickness of the dielectric plate, ε eff is the effective relative dielectric constant, a is the patch length, b is the patch width, and f is the center frequency.r is the dielectric constant, c is the speed of light, λ e is the effective wavelength.

[0020] Furthermore, in step 2, the left-hand circularly polarized vortex beam circular array and the right-hand circularly polarized vortex beam circular array extract three degrees of freedom, including the first degree of freedom being array element polarization, including linear polarization and circular polarization; the second degree of freedom being array element arrangement; and the third degree of freedom being feed excitation phase distribution.

[0021] Furthermore, in step 2, the array elements of the left-hand circularly polarized vortex beam ring array and the right-hand circularly polarized vortex beam ring array are arranged in such a way that N array elements are evenly arranged on a ring with a radius of r, and the corresponding azimuth angle can be expressed as:

[0022] φ n =2πn / N(n=1,2...N)

[0023] φ n is the azimuth angle corresponding to the nth array element;

[0024] The nth array element has a certain rotation angle, whose value is a multiple of the corresponding azimuth angle:

[0025]

[0026]

[0027] l1 is the number of rotation angle modes in the left-hand circularly polarized vortex beam ring array, and l1′ is the number of rotation angle modes in the right-hand circularly polarized vortex beam ring array.

[0028] Furthermore, in step 2, the feed excitation phase distribution is gradient phase excitation;

[0029] The left-hand circularly polarized vortex beam ring array and the right-hand circularly polarized vortex beam ring array are both gradient phase excited, and the excitation phase corresponding to the nth array element is β n , in gradient phase excitation:

[0030] β n =l2φ n

[0031] β n =l2′φ n

[0032] l2 is the number of excited phase modes in the left-hand circularly polarized vortex beam ring array, and l2′ is the number of excited phase modes in the right-hand circularly polarized vortex beam ring array.

[0033] The beneficial effects achieved by the present invention are:

[0034] The application firstly proposes three degrees of freedom of circular array radiation field regulation, i.e., array element polarization, array element arrangement mode and excitation phase mode; secondly, the three degrees of freedom are combined and analyzed, and a multi-degree-of-freedom circular array vortex beam generation method based on any combination of the three degrees of freedom is obtained through theoretical derivation. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structure diagram of left-handed circular polarization unit I.

[0036] Figure 2 It is a structure diagram of right-handed circular polarization unit II.

[0037] Figure 3 It is a simulation return loss of left-handed and right-handed circular polarization units.

[0038] Figure 4 It is a simulation axial ratio of left-handed and right-handed circular polarization units.

[0039] Figure 5 It is an electric field change process in one period of left-handed circular polarization unit I.

[0040] Figure 6 It is an electric field change process in one period of right-handed circular polarization unit II.

[0041] Figure 7 It is a simulation far-field pattern of left-handed and right-handed circular polarization units at a center frequency band.

[0042] Figure 8 It is a feeding network structure of left-handed circular polarization array A.

[0043] Figure 9 It is a feeding network structure of right-handed circular polarization array B.

[0044] Figure 10 It is a comparison curve of target phase and actual phase of each port.

[0045] Figure 11 It is a general structure diagram of left-handed circular polarization array A.

[0046] Figure 12 It is a general structure diagram of right-handed circular polarization array B.

[0047] Figure 13 It is a processing sample diagram of left-handed circular polarization circular array A.

[0048] Figure 14 It is a processing sample diagram of right-handed circular polarization circular array B.

[0049] Figure 15 It is a simulation and test return loss of left-handed circular polarization circular array A.

[0050] Figure 16 The simulation and test echo reflection coefficient of the right-handed circularly polarized circular array B.

[0051] Figure 17 The far-field test far-field pattern. Wherein (a) is a far-field experimental platform, (b) is the simulation and test far-field pattern of array A at 9.08 GHz, (c) is the simulation and test far-field pattern of array B at 13.45 GHz.

[0052] Figure 18 The far-field test far-field pattern. Wherein (a) is a far-field experimental platform, (b) is the simulation and test far-field pattern of array A at 9.08 GHz, (c) is the simulation and test far-field pattern of array B at 13.45 GHz. DETAILED DESCRIPTION

[0053] The technical solutions of the present application will be described in more detail below in conjunction with the drawings. The present application includes but is not limited to the following embodiments.

[0054] As shown in the accompanying Figure 1 , the present application proposes a three-degree-of-freedom circular array vortex beam generation method, including the following steps:

[0055] Step 1, design left-handed circularly polarized units and right-handed circularly polarized circular array units for generating three-degree-of-freedom vortex beams;

[0056] In the circular array, different mode numbers of vortex beams are generated by combining the polarization, rotation angle and excitation phase freedom of the units. Based on this, the present application designs two kinds of orthogonal circularly polarized units.

[0057] Each unit is a rectangular patch with an inclined diagonal slot, and the diagonal slot directions of the two units are orthogonal. Each unit is composed of an F4B dielectric plate, the dielectric constant is ε r = 2.65, the electric tangent loss is tan δ = 0.001, the length, width and height of the dielectric plate of the left-handed circularly polarized unit are g a , g b , h1 respectively; the length, width and height of the dielectric plate of the right-handed circularly polarized unit are g a , g b, h2. The radii of the circular rings in which the two units are distributed are r1 and r2 respectively. The metal structural material is copper, the conductivity of which is σ = 5.8 × 107S / m, and the thickness is 0.018 mm; the length and width of the rectangular radiation patch of the left-handed circularly polarized unit are a1 and b1 respectively, the corresponding oblique diagonal slot length and width are L1 + L2 and w1 respectively, the oblique angle is j1, and the corresponding feed line width is w2; the length and width of the rectangular radiation patch of the right-handed circularly polarized unit are a2 and b2 respectively, the corresponding oblique diagonal slot length and width are L3 + L4 and w4 respectively, the oblique angle is j2, and the corresponding feed line width is w5.

[0058] First, the approximate range of the patch is determined by the formula, then the patch is added with a feed line and a slot, the direction of the slot corresponding to different polarization units is determined through simulation results, then a large number of parameter scanning is performed on the two units to better match the impedance, so as to determine the final result.

[0059] According to the application requirements, a radiation patch with a suitable shape is selected, by comparing the performance of rectangular, triangular and circular patches, a rectangular patch with larger bandwidth, stronger directivity and better energy radiation efficiency is selected. According to the open microstrip line edge expansion length ΔL analysis formula and the rectangular patch antenna resonance formula, the side length of the rectangular radiation patch can be calculated.

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] In the formula, ΔL is the microstrip line edge expansion length, h is the thickness of the dielectric plate, ε eff is the effective relative dielectric constant, a is the patch length, b is the patch width, f is the center frequency, ε r is the dielectric constant, c is the speed of light, and λ e is the effective wavelength.

[0067] The single-layer rectangular patch antenna is a linearly polarized antenna, in order to meet the design requirements of the circularly polarized unit, the unit is improved by adding a slot perturbation structure, Figure 1 is a left-handed circularly polarized unit I working at 9.43 GHz, Figure 2Unit II is right-handed circularly polarized unit working at 13.59 GHz. The slot directions of the two unit structures are orthogonal. After the energy is transmitted to the patch through the port, the current moving on both sides of the slot will generate a certain 90° phase difference in two orthogonal directions, so that the radiation beam is circularly polarized wave. The specific parameters of the unit structure are as follows: the thickness of the dielectric plate is h1=h2=1.5 mm, the side length of the rectangular radiation patch is a1=8.1 mm, b1=8 mm; a2=b2=5.2 mm, the slot side length is L1=2.6 mm, L2=2.7 mm; L3=2.1 mm, L4=2 mm, w1=0.7 mm, w4=1 mm, the slot rotation angle is j1=50°; j2=55°, the width of the feed line is w2=w5=0.8 mm, the bottom ground plate metal is copper, the conductivity is σ=5.8×107S / m, and the thickness is 0.018 mm.

[0068] The unit simulation S parameter condition is shown in Figure 3 From the figure, it can be seen that the S 11 Impedance bandwidth below-10dB of unit I is 8.6%(9.16-9.99GHz), and the S 11 Impedance bandwidth below-10dB of unit II is 11.5%(13.06-14.66GHz). The unit simulation axial ratio condition is shown in Figure 4 From the figure, it can be seen that the bandwidth of unit I axial ratio below-3dB is 1.64%(9.37-9.53GHz), and the bandwidth of unit II axial ratio below-3dB is 1.7%(13.38-13.61GHz). The above results show that the impedance bandwidth of the two units covers the axial ratio bandwidth, and has good circular polarization characteristics at the corresponding frequency band.

[0069] From the unit structure diagram, it can be seen that the two unit structures are similar, but the rectangular aperture rotation directions are opposite. It is the opposite rotation angle that leads to different polarization of the unit radiated electromagnetic wave. In order to better understand the electric field state of the two units when working in polarization, Figure 5 and Figure 6 The electric field variation process of the two units in a period at the corresponding resonance frequency is given. From the figure, it can be seen that the surface electric field of the two units rotates around the rectangular aperture when the phase changes, but the rotation directions are opposite. The electric field of unit I rotates clockwise, and the electric field of unit II rotates counterclockwise. This electric field trajectory verifies that the polarization of the two radiation beams is left-handed circular polarization and right-handed circular polarization respectively.

[0070] Figure 7The far field patterns of the two units at their corresponding center frequency bands are given. It can be clearly seen from the figures that the main polarization of unit I is left-handed circular polarization, the main polarization energy decreases less than -3dB in the range of -39°-39°, and the cross polarization relative to the main polarization is lower than -17dB in the whole space. The main polarization of unit II is right-handed circular polarization, the main polarization energy decreases less than -3dB in the range of -57°-50°, and the cross polarization relative to the main polarization is lower than -15dB in the whole space. The above analysis shows that both units have good circular polarization characteristics.

[0071] Step 2, design left-handed circular polarization vortex beam circular array and right-handed circular polarization vortex beam circular array based on left-handed circular polarization unit and right-handed circular polarization circular ring unit respectively;

[0072] Three degrees of freedom are extracted from the circular array, the first degree of freedom is the polarization of the array element, which can be divided into linear polarization and circular polarization.

[0073] The second degree of freedom is the arrangement mode of the array element, which can be divided into rotating arrangement and same direction (no spatial rotation of the element) arrangement according to whether the element is rotated. The difference between the two arrangements is whether there is a rotation angle of the element. As can be seen from the drawings, both array structures are composed of N elements uniformly arranged on a circular ring with a radius of r, and the azimuth angle corresponding to the nth element is φ n Since the elements are uniformly arranged, the corresponding azimuth angle can be expressed as φ n = 2πn / N (n = 1, 2...N). In the rotating arrangement array, it is assumed that the nth element has a certain rotation angle, which is a multiple of the corresponding azimuth angle, i.e. or In the formula, l1 is the mode number of the rotation angle in the left-handed circular polarization vortex beam circular array, l1' is the mode number of the rotation angle in the right-handed circular polarization vortex beam circular array, and in the same direction arrangement array, the element has no rotation angle. Both the two array structures shown in the drawings are rotating arrangement arrays, l1 = 1 in the left-handed circular polarization vortex beam circular array, and l1' = 2 in the right-handed circular polarization vortex beam circular array.

[0074] The third degree of freedom is the phase distribution of the feeding excitation, which can be divided into gradient phase excitation and in-phase excitation. The excitation phase corresponding to the nth element is denoted as β n In the gradient phase excitation, β n = l2φ n or β n = l2'φ n , in which l2 is the mode number of the excitation phase in the left-handed circular polarization vortex beam circular array, and l2' is the mode number of the excitation phase in the right-handed circular polarization vortex beam circular array. In the in-phase excitation, l2 = 0, l2' = 0, and β n= 0. The left-handed circularly polarized vortex beam circular array and the right-handed circularly polarized vortex beam circular array are both gradient phase excitations, and in the left-handed circularly polarized vortex beam circular array, l2= -1, and in the right-handed circularly polarized vortex beam circular array, l2'= -1.

[0075] Based on the left-handed circularly polarized element and the right-handed circularly polarized element, a left-handed circularly polarized vortex beam circular array capable of generating a vortex mode of l = -2 and a right-handed circularly polarized vortex beam circular array capable of generating a vortex mode of l = 1 are respectively designed. ′

[0076] Step 3, generating a three-degree-of-freedom circular array vortex beam based on the left-handed circularly polarized vortex beam circular array and the right-handed circularly polarized vortex beam circular array;

[0077] According to the above analysis, there are three degrees of freedom in the circular array, and the cross combination of the degrees of freedom will produce eight different arrays. Next, the formula derivation and analysis of the eight cases will be carried out to explore the scheme that can produce vortex beams.

[0078] When the element polarization is linear polarization, different element arrangement modes and different excitation phases are analyzed. When the element polarization is linear polarization, the excitation electric field corresponding to the nth element can be decomposed into two vectors, that is:

[0079]

[0080] In the formula, θn is the spin angle of the element, is the x-direction vector vector, is the y-direction vector vector.

[0081] Let the excitation current of the nth element be In the formula, In is the excitation amplitude of the nth element, and βn is the excitation phase of the nth element. n n At this time, the x-polarization direction far-field intensity can be expressed as:

[0082]

[0083] Its array factor can be expressed as:

[0084]

[0085] Since the exponential term can be expanded by using the Bessel function, that is:

[0086]

[0087] Substitute formula (6) into (5) and simplify by Euler formula. At this time, the array factor can be expressed as: ​​​

[0088]

[0089] Switching the summation order of the above formula:

[0090]

[0091] By the formula of the sum of geometric series:

[0092]

[0093] Therefore, let be an even number 2t, at this time the array factor can be expressed as:

[0094]

[0095] Similarly, the array factor of the y polarization direction can be expressed as:

[0096]

[0097] At this time, the array factor of the array can be expressed as:

[0098]

[0099] From the Bessel function, the main term of the function is located at t = 0, which is substituted into the above array factor, it can be known that the array factor of the x polarization and the y polarization direction both exist two exponential terms, that is, and

[0100] At this time, if l1 = l2 = 0, that is, the same direction array and the excitation phase is in-phase excitation, there is no vortex beam characteristic phase e jlφ in the array factor at this time, which cannot generate a vortex beam.

[0101] If l1 = 0, l2 ≠ 0, that is, the same direction array and the excitation phase is gradient phase excitation, the array factor contains phase at this time, which will generate a vortex beam with a mode number equal to the mode of the excitation phase.

[0102] If l1 ≠ 0, l2 = 0, that is, the rotating array and the excitation phase is in-phase excitation, the array factor contains and phase at this time, which cannot generate a vortex beam with pure mode.

[0103] If l1 ≠ 0, l2 ≠ 0, that is, the rotating array and the excitation phase is gradient phase excitation, the array factor contains and phase at this time, which cannot generate a vortex beam with pure mode.

[0104] In summary, when the elements in the circular array are linearly polarized elements, the vortex beam with the mode number equal to the excitation phase mode can be generated if and only if the array is co-directional and the excitation phase is gradient phase excitation.

[0105] For the circularly polarized elements, different element arrangement modes and different excitation phases are analyzed. The analysis of circularly polarized elements is similar to that of linearly polarized elements. Since circular polarization can be decomposed into two orthogonal linear polarizations, when the elements are left-handed circularly polarized, the excitation electric field can be expressed as:

[0106]

[0107] From equations (11) and (12), it can be seen that the array factor of the circular array can be expressed as:

[0108]

[0109] Similarly, when the elements are right-handed circularly polarized, the excitation electric field is:

[0110]

[0111] At this time, the array factor of the circular array can be expressed as:

[0112]

[0113] From the above analysis, when the elements are left-handed circularly polarized or right-handed circularly polarized, if l1 = l2 = 0, i.e., the array is co-directional and the excitation phase is in-phase excitation, there is no vortex beam characteristic phase e jlφ in the array factor at this time, and vortex beams cannot be generated, only circularly polarized beams with the same polarization as the elements can be generated.

[0114] In addition, when the elements are left-handed circularly polarized, if l1 ≠ 0 and l2 ≠ 0, the array can generate left-handed circularly polarized vortex beams with a mode number of l2 - l1. When the elements are right-handed circularly polarized, if l1 ≠ 0 and l2 ≠ 0, the array can generate right-handed circularly polarized vortex beams with a mode number of l1 + l2.

[0115] From the above theoretical derivation, to realize a vortex beam with a mode of l = -2, the left-handed circularly polarized elements need to be excited with an excitation phase mode of l2 = -1, and the right-handed circularly polarized elements also need an excitation phase of l2 ′ = -1 to realize a vortex beam with a mode of l ′ = 1. Therefore, the feed network needs to be carefully designed to meet the above excitation phase requirements. The feed network is composed of a power divider, a stepped impedance matching device, and a phase shifter. The final layout of the feed network is as Figure 8 , Figure 9To verify that the excitation phase given by the feeding network satisfies l2=l2 ′ =-1, Figure 10 The target phase and actual phase comparison curves of each port are given. As can be seen from the figure, the excitation phase achieved by the two feeding networks is well consistent with the target phase, and the purpose of phase control can be achieved.

[0116] Through the above work, the design of three degrees of freedom, namely, array element polarization, array element rotation angle and excitation phase, has been completed. Next, the array elements and feeding network will be assembled to realize a complete circular array. The final left-hand circularly polarized array A array layout is as follows Figure 11 As shown, the right-hand circularly polarized array B array layout is as follows Figure 12 shown.

[0117] To verify the theoretical accuracy and performance of the array model, the two proposed arrays were simulated, fabricated, and tested. HFSS, a commercial 3D structural electromagnetic field simulation software, was used to simulate and verify the array samples. Subsequently, a combination of CAD and PCB technology was used to fabricate the array samples. Figure 13 To realize the left-hand circular polarization ring array A sample with the vortex mode number l=-2 by using the left-hand circular polarization unit; Figure 14 To achieve a vortex mode number of l using a right-hand circularly polarized unit ′ =1 right-hand circularly polarized ring array B sample.

[0118] In order to verify the impedance characteristics of the two arrays, S-parameter tests were performed on them using a vector network analyzer. Figure 15 The simulation and test S-parameter results of the ring array A are given. It can be seen from the figure that the center frequency of the array I is 9.08GHz, and the corresponding impedance bandwidth is; Figure 16 The simulation and test S-parameter results for Ring Array B are shown. As can be seen from the figure, the center frequency of Array II is 13.45 GHz, and the corresponding impedance bandwidth is . The simulation and test result curves for the two arrays have roughly the same trend.

[0119] In order to verify the performance of the vortex beam generated by the array, a far-field experimental test of the array was carried out. Figure 17 (a) shows the far-field experimental platform. The platform is located in a microwave anechoic chamber, with the array sample placed in the center of a mechanical control console. A standard circularly polarized horn, serving as the receiving antenna, is positioned 12 meters from the array sample. During testing, the console rotates, allowing the receiving horn to measure the array sample's far-field pattern within the xoz plane. Figure 17(b) gives the simulation and experimental far-field patterns of array A at 9.08 GHz, and it can be seen from the figure that the simulation and experimental results are consistent with each other. In the simulation, the beam results of different polarizations are extracted, and the results of receiving the electromagnetic beam of the array antenna by the receiving horn through different polarizations in the experiment are all vortex zero depth phenomena at the left-handed polarization beam θ = 0°, which indicates that the main polarization of array A is left-handed circular polarization, and the peak value is located at both sides of the zero depth ± 27°, which is consistent with the characteristics of vortex beam. Figure 17 (c) is the simulation and experimental far-field patterns of array B at 13.45 GHz, and the simulation and experimental results both show that the right-handed circular polarization is the main polarization of array B, and the vortex zero depth phenomenon also occurs at θ = 0°, and the peak value is located at both sides of the zero depth ± 13.5°. The far-field simulation and experiment both verify that the beams generated by the two arrays are vortex beams, and the peak value range of array A is larger than that of array B, which is consistent with the expected vortex mode l = -2, l' = 1.

[0120] In order to further characterize the mode characteristics of the vortex beam, the near-field scanning experiments of the two arrays are carried out. Figure 18 (a) is a near-field scanning experimental platform, in which the array sample is fixed on the metal support through the foam board, the standard spiral antenna is used as the receiving antenna and is placed at a distance of 20 cm from the sample and is connected with the near-field scanning instrument. When the near-field scanning test is carried out, the array sample will radiate electromagnetic energy, and at the same time the near-field scanning instrument will drive the spiral antenna to carry out near-field scanning in the xoy plane, and the scanning range is 15 cm x 15 cm and the step is 5 mm. The near-field scanning amplitude results of array A at 9.08 GHz and array B at 13.45 GHz are shown in Figure 18 (b) and Figure 18 (c), and it can be seen from the figure that the amplitudes of the two arrays are in the shape of "donut", which is consistent with the amplitude distribution characteristics of the vortex beam. In order to further prove the corresponding mode number of the vortex beam, Figure 18 (d) and Figure 18 (e) gives the corresponding phase distribution, and it can be seen that the near-field phase of array A covers 720°. The near-field phase of array B covers 360° and the rotation directions are opposite, which powerfully proves that the corresponding mode numbers of the vortex beams radiated by the two arrays are l = -2, l ′ = 1, which verifies the correctness of the theory and model.

[0121] The present application is not limited to the above-mentioned specific embodiments, and those skilled in the art can use other various specific embodiments to implement the present application according to the content disclosed in the embodiments and the drawings, therefore, any design that uses the design structure and idea of the present application and makes some simple changes or modifications falls within the protection scope of the present application.

Claims

1. A three-degree-of-freedom circular array vortex beam generation method, characterized in that: The three-degree-of-freedom circular ring array vortex beam generation method comprises the following steps: Step 1, designing a left-hand circular polarization unit and a right-hand circular polarization ring unit for generating a three-degree-of-freedom vortex beam; Step 2, designing a left-hand circularly polarized vortex beam ring array and a right-hand circularly polarized vortex beam ring array based on the left-hand circularly polarized unit and the right-hand circularly polarized ring unit respectively; Step 3, generating a three-degree-of-freedom circular array vortex beam based on the left-hand circular polarization vortex beam circular array and the right-hand circular polarization vortex beam circular array; The left-hand circular polarization unit and the right-hand circular polarization ring unit are in a circular array, and both the left-hand circular polarization unit and the right-hand circular polarization ring unit are rectangular patches with inclined diagonal slots, and the diagonal slots of the two units are orthogonal; the left-hand circular polarization unit and the right-hand circular polarization ring unit are both composed of F4B dielectric plates; When the array element polarization is left-hand circular polarization, if the rotation angle mode number l1 in the left-hand circular polarization vortex beam ring array is ≠ 0 and the excitation phase mode number l2 in the left-hand circular polarization vortex beam ring array is ≠ 0, the array can generate a left-hand circular polarization vortex beam with a mode number of l2-l1; When the array element polarization is right-hand circular polarization, if the rotation angle mode number l1′ in the right-hand circularly polarized vortex beam ring array is ≠0 and the excitation phase mode number l2′ in the right-hand circularly polarized vortex beam ring array is ≠0, the array can generate a right-hand circularly polarized vortex beam with a mode number of l1′+l2′.

2. The three-degree-of-freedom circular array vortex beam generation method according to claim 1, characterized in that: In step 1, The dielectric constant of the F4B dielectric plate of the left-hand circular polarization unit and the right-hand circular polarization ring unit is ε r =2.65, the electrical tangent loss is tanδ=0.001, and the length, width and height of the dielectric plate of the left-hand circularly polarized unit are g a 、g b , h1; the right-handed circularly polarized ring unit dielectric plate length, width, height, respectively g a 、g b , h2; the radii of the circular rings distributed by the two units are r1 and r2 respectively; the metal structure materials are all copper, its electrical conductivity is σ=5.8×107S / m, and its thickness is 0.018mm; the length and width of the rectangular radiation patch of the left-hand circular polarization unit are a1 and b1 respectively, and the length and width of the corresponding inclined diagonal gap are L1+L2 respectively, the width is w1, the tilt angle is j1, and the corresponding feeder width is w2; the length and width of the rectangular radiation patch of the right-hand circular polarization ring unit are a2 and b2 respectively, and the length and width of the corresponding inclined diagonal gap are L3+L4 respectively, the width is w4, the tilt angle is j2, and the corresponding feeder width is w5.

3. The three-degree-of-freedom circular array vortex beam generation method according to claim 2, characterized in that: In step 1, the side length of the radiation patch is obtained according to the open microstrip line edge extension length ΔL analysis formula and the rectangular patch antenna resonance formula: Where ΔL is the extension length of the microstrip line edge, h is the thickness of the dielectric plate, and ε eff is the effective relative dielectric constant, a is the patch length, b is the patch width, f0 is the center frequency, ε r is the dielectric constant, c is the speed of light, λ e is the effective wavelength.

4. The three-degree-of-freedom circular array vortex beam generation method according to claim 1, characterized in that: In step 2, the left-hand circularly polarized vortex beam circular array and the right-hand circularly polarized vortex beam circular array extract three degrees of freedom, including the first degree of freedom being the array element polarization, including linear polarization and circular polarization; the second degree of freedom being the array element arrangement; and the third degree of freedom being the feed excitation phase distribution.

5. The three-degree-of-freedom circular array vortex beam generation method according to claim 4, characterized in that: In step 2, the array elements of the left-hand circularly polarized vortex beam ring array and the right-hand circularly polarized vortex beam ring array are arranged in such a way that N array elements are evenly arranged on a ring with a radius of r. The corresponding azimuth angle can be expressed as: f n =2πn / N(n=1,2...N) φ n is the azimuth angle corresponding to the nth array element; The nth array element has a certain rotation angle, whose value is a multiple of the corresponding azimuth angle: l1 is the number of rotation angle modes in the left-hand circularly polarized vortex beam ring array, l1 ′ is the number of rotation angle modes in the right-hand circularly polarized vortex beam ring array.

6. The three-degree-of-freedom circular array vortex beam generation method according to claim 5, characterized in that: In step 2, the feed excitation phase distribution is gradient phase excitation; The left-hand circularly polarized vortex beam ring array and the right-hand circularly polarized vortex beam ring array are both gradient phase excited, and the excitation phase corresponding to the nth array element is β n , in gradient phase excitation: b n =l2φ n b n =l2′φ n l2 is the number of excited phase modes in the left-hand circularly polarized vortex beam ring array, and l2′ is the number of excited phase modes in the right-hand circularly polarized vortex beam ring array.

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