Two-dimensional antenna array multi-beam scanning method based on holographic amplitude weighting

Abstract

The invention relates to the technical field of wireless communication and sensing, and particularly discloses a holographic amplitude weighting-based two-dimensional antenna array multi-beam scanning method, which comprises the following steps of: determining the position information of each radiation unit in a two-dimensional antenna array, including calculating the interval and the arrangement mode of the units; an amplitude weighted value of each radiation unit is generated according to the target wave direction, a two-dimensional multi-beam holographic amplitude weighting technology is used, and the radiation unit amplitude weighted values are determined through the two-dimensional multi-beam holographic amplitude weighting technology; generating a corresponding binary discretization coding sequence based on the amplitude weighted value so as to control the excitation amplitude of each radiation unit; and designing a liquid crystal-based Ka-band two-dimensional holographic beam scanning leaky-wave antenna square array, and regulating and controlling a radiation pattern of a two-dimensional antenna array through the coding sequence to realize multi-beam scanning.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless communication and sensing technology, and particularly relates to a two-dimensional antenna array multi-beam scanning method based on holographic amplitude weighting. BACKGROUND

[0002] Currently, the demand for wireless communication and sensing technology is growing, especially in the fields of 5G / 6G millimeter wave communication, satellite communication, high-precision radar, and Internet of Things. These application scenarios have higher requirements for antenna systems, including the ability to achieve high gain, narrow beam, multi-beam simultaneous operation, fast beam scanning, and compact integration. Antenna arrays, as the key components to achieve these functions, their beam scanning capability is the core. Traditional beam scanning methods, such as phase control through phase shifters (analog beamforming) or using complex digital signal processing (digital beamforming), often face problems such as high cost, complex system, high power consumption, or limited scanning speed.

[0003] In recent years, antenna design based on holographic principles has provided a novel and promising approach to beam scanning. Holographic antennas control the distribution of electromagnetic fields on the antenna aperture precisely, thereby forming the desired radiation pattern in the far field. Among them, holographic amplitude weighting as an important holographic technology, its core idea is to adjust the radiation amplitude of the antenna array elements to synthesize the required hologram, and then form a specific beam. This technology has unique advantages in leaky-wave antenna design, as it can achieve continuous beam scanning and more flexible beam shaping capabilities.

[0004] Leaky-wave antennas are a type of traveling-wave antenna, which have the advantages of high gain, low profile, simple feed system, and good beam scanning compared to traditional mechanical scanning antennas and electrically controlled scanning antennas. Traditional leaky-wave antennas are frequency-scan antennas, i.e., the main beam changes with frequency. However, due to the increasing scarcity of spectrum resources, this frequency-scan characteristic limits the application range of the antenna. Therefore, designing a fixed-frequency beam scanning leaky-wave antenna has become an important research topic.

[0005] At present, loading PIN diode or varactor diode and other active devices is a common method to realize the fixed frequency beam scanning of leaky-wave antenna, but the main disadvantage is that it cannot be well used in millimeter wave band or even higher frequency band, and the application frequency band is not high; adding graphene, ferrite and other tunable materials in the antenna unit can also realize fixed frequency beam scanning, but there is a problem that the loss increases with the increase of frequency band. In recent years, liquid crystal material has been applied to reconfigurable antenna field due to its excellent performance of high frequency band and low loss. Compared with active devices and other tunable materials, liquid crystal material has a wider application frequency range, which can be from 10GHz to optical frequency band, and the insertion loss decreases with the increase of frequency band, which can be well applied to high frequency band antenna design. Therefore, liquid crystal material has broad application prospect in the design of fixed frequency beam scanning leaky-wave antenna.

[0006] Holographic amplitude weighting technology is a key technology to realize fixed frequency beam scanning leaky-wave antenna, and the variable dielectric constant of liquid crystal material can be well combined with holographic amplitude weighting technology to complete the beam scanning task, so the design and research of holographic beam scanning leaky-wave antenna based on liquid crystal has important value. At the same time, existing research has proved the theoretical feasibility of holographic amplitude weighting technology in one-dimensional leaky-wave antenna array single beam scanning and multi-beam scanning and two-dimensional leaky-wave antenna array single beam scanning, that is, most of the research on beam scanning leaky-wave antenna only realizes single beam scanning, and the research on multi-beam is limited, especially the method of two-dimensional leaky-wave antenna multi-beam scanning is lacking.

[0007] Therefore, in order to better meet the demand of millimeter wave satellite communication, in view of the problems of few multi-beam scanning methods of two-dimensional antenna array, insufficient beam control flexibility and large high frequency loss in the prior art, based on the existing theory of holographic amplitude weighting of leaky-wave antenna beam scanning, a two-dimensional multi-beam scanning method based on holographic amplitude weighting is proposed, and a two-dimensional leaky-wave antenna array based on liquid crystal metamaterial is designed, and the effectiveness and feasibility of the method are verified. SUMMARY

[0008] To achieve the purpose of the application, the application provides a two-dimensional antenna array multi-beam scanning method based on holographic amplitude weighting, comprising:

[0009] Step S1: determining the position information of each radiating unit in the two-dimensional antenna array, including unit spacing and arrangement mode;

[0010] Step S2: generating the amplitude weighting value of each radiating unit according to the target beam pointing, using two-dimensional multi-beam holographic amplitude weighting technology, the amplitude weighting value of the radiating unit is determined by the two-dimensional multi-beam holographic amplitude weighting technology;

[0011] Step S3: generating a corresponding binary discretization encoding sequence based on the amplitude weighting value to control the excitation amplitude of each radiation unit;

[0012] Step S4: designing a liquid crystal-based Ka-band two-dimensional holographic beam scanning leaky-wave antenna array, regulating the radiation pattern of the two-dimensional antenna array through the encoding sequence to realize multi-beam scanning.

[0013] In some embodiments, in step S1, the two-dimensional antenna array comprises:

[0014] a plurality of periodically arranged radiation units, each radiation unit comprising a complementary open resonant ring slot structure and a liquid crystal layer;

[0015] a center feeding structure for providing a reference wave to the radiation units;

[0016] a control module for generating an encoding sequence and regulating the excitation amplitude of each radiation unit through the encoding sequence.

[0017] In some embodiments, in step S2, the amplitude weighting value is determined by the following method:

[0018] generating a holographic pattern based on the interference effect of the reference wave and the target wave;

[0019] correcting the phase of the holographic pattern by solving the beam center depression problem existing in the two-dimensional array;

[0020] determining the contribution rate of each radiation unit to the target beam pointing through the holographic pattern;

[0021] discretizing the contribution rate to obtain a binary discretization encoding sequence.

[0022] In some embodiments, the reference wave is determined according to the center feeding structure, and the target wave is determined according to the expected beam pointing.

[0023] In some embodiments, the target wave, the holographic pattern and the amplitude weighting function are determined according to the following formula:

[0024]

[0025] wherein y n represents the longitudinal coordinate of the nth radiation unit and the excitation source, x m represents the transverse coordinate of the mth radiation unit and the excitation source, k ref represents the propagation constant of the reference wave in the transmission medium, k0 represents the propagation constant in free space at the same frequency, and θ0 represents the target beam elevation angle pointing, represents the target beam horizontal angle pointing.

[0026] In some embodiments, the target wave and the amplitude weighting function are determined according to the following formula:

[0027]

[0028] wherein y n represents the longitudinal coordinate of the nth radiation unit and the excitation source, x m represents the transverse coordinate of the mth radiation unit and the excitation source, k0 represents the propagation constant in free space at the same frequency, θ g represents the beam pointing of the gth elevation angle, represents the beam pointing of the tth horizontal angle, G represents the number of target beam elevation angles, T represents the number of target beam horizontal angles, g represents the gth target elevation angle, and t represents the tth target horizontal angle.

[0029] In some embodiments, in step S3, the beam scanning function of the two-dimensional leaky-wave antenna array is realized by weighting and regulating the excitation amplitude of each unit in combination with the holographic antenna principle and the amplitude weighting technology.

[0030] In some embodiments, in step S3, the two-dimensional leaky-wave antenna array respectively adopts a continuous amplitude weighting excitation amplitude function and a discrete amplitude weighting excitation amplitude function.

[0031] In some embodiments, the continuous amplitude weighting excitation amplitude function is determined according to the following formula after solving the problem of beam center depression:

[0032]

[0033] wherein k ref represents the propagation constant of the reference wave in the transmission medium, k0 represents the propagation constant in free space at the same frequency, θ g represents the beam pointing of the gth elevation angle, represents the beam pointing of the tth horizontal angle, G represents the number of target beam elevation angles, T represents the number of target beam horizontal angles, g represents the gth target elevation angle, and t represents the tth target horizontal angle.

[0034] In some embodiments, the discrete amplitude weighting excitation amplitude function is determined according to the following formula:

[0035]

[0036] wherein θ g represents the beam pointing of the gth elevation angle, represents the beam pointing of the tth horizontal angle.

[0037] The technical scheme has the beneficial effects that:

[0038] Compared with the prior art, the holographic amplitude weighting-based two-dimensional antenna array multi-beam scanning method and the designed liquid crystal-based two-dimensional beam scanning leaky-wave antenna array have the following remarkable technical effects and beneficial effects:

[0039] 1. Beam scanning capability is improved:

[0040] The application proposes a holographic amplitude weighting-based two-dimensional leaky-wave antenna array multi-beam scanning method, which can simultaneously generate multiple beams and control the scanning of the beams in a two-dimensional space through coding switching, thereby expanding the application range of the antenna array.

[0041] 2. Performance advantage:

[0042] The antenna is miniaturized, has a wide beam scanning range and high gain: the designed antenna unit and array have the advantages of low profile and small volume. Simulation results show that the Ka-band two-dimensional holographic leaky-wave antenna square array designed by the application can not only realize single-beam scanning in the range of -36° to 40° in the azimuth angle and -60° to 38° in the elevation angle , but also realize double-beam / three-beam scanning in the range of -30° to 30° in the azimuth angle and -60° to 30° in the elevation angle, with a gain of more than 12 dB. Compared with the two-dimensional leaky-wave antenna which can only realize single-beam scanning, the application has remarkable advantages in scanning range and beam number.

[0043] Application scenario expansion: the two-dimensional multi-beam scanning capability enables the antenna array to simultaneously cover multiple targets or perform more flexible signal processing in complex environments, and is suitable for various application scenarios such as radar, communication and remote sensing. Meanwhile, considering that the leaky-wave antenna unit or array can be used as a unit antenna of a comprehensive aperture array in the future, the small and compact planar structure (such as a rectangular slot waveguide or a microstrip patch array) can be directly embedded in the sparse array of the comprehensive aperture array to replace the traditional horn or dipole unit.

[0044] 3. Efficiency is improved:

[0045] In the simulation design process of the two-dimensional leaky-wave antenna array, the application adopts a Python-HFSS (PH) control coding method, which greatly improves the coding efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. ​

[0047] Figure 1 Radiation pattern of leaky-wave antenna provided for an embodiment of the application;

[0048] Figure 2 Schematic diagram of holographic antenna beam control method based on binary weighting provided for an embodiment of the application;

[0049] Figure 3 Schematic diagram of two-dimensional array structure provided for an embodiment of the application;

[0050] Figure 4 N x ×N y Schematic diagram of planar antenna array provided for an embodiment of the application;

[0051] Figure 5 (a) front view, (b) top view, (c) side view of antenna unit structure provided for an embodiment of the application;

[0052] Figure 6 Schematic diagram of two-dimensional leaky-wave antenna unit performance simulation provided for an embodiment of the application;

[0053] Figure 7 Distribution diagram of electric field energy (a) and magnetic field energy (b) at CSRR slot provided for an embodiment of the application;

[0054] Figure 8(a) is a top view of two-dimensional holographic leaky-wave antenna structure provided for an embodiment of the application;

[0055] Figure 8(b) is a side view of two-dimensional holographic leaky-wave antenna structure provided for an embodiment of the application;

[0056] Figure 9 Holographic distribution diagram provided for an embodiment of the application θ=0°;

[0057] Figure 10 Far-field beam pattern provided for an embodiment of the application θ=0°;

[0058] Figure 11 Holographic distribution diagram provided for an embodiment of the application θ=0° after modifying the phase;

[0059] Figure 12 Far-field beam pattern provided for an embodiment of the application θ=0° after modifying the phase;

[0060] Figure 13 Holographic distribution diagram provided for an embodiment of the application Antenna array hologram distribution diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°;

[0061] Figure 14 Antenna array hologram distribution diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°; Beam gain diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°;

[0062] Figure 15 Beam gain diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°; S11 parameter diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°;

[0063] Figure 16 Antenna gain diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°; (b) (c) (d)

[0064] Figure 17 Antenna gain diagrams corresponding to different beam pointing directions, (a) θ = 0°; (b) θ = -30°; (c) θ = 30°; (d) θ = -60°; (e) θ = 40°; Antenna array hologram distribution diagrams corresponding to different multi-beam pointing directions, (a) θ = -10° / 10°; (b) θ = -20° / 20°; (c) θ = -30° / 30°; (d) θ = -60° / 0°; (e) θ = -30° / 0° / 30°; (f) θ = -60° / -30° / 0°;

[0065] Figure 18 Antenna array hologram distribution diagrams corresponding to different multi-beam pointing directions, (a) θ = -10° / 10°; (b) θ = -20° / 20°; (c) θ = -30° / 30°; (d) θ = -60° / 0°; (e) θ = -30° / 0° / 30°; (f) θ = -60° / -30° / 0°; Beam gain diagrams corresponding to different multi-beam pointing directions, (a) θ = -10° / 10°; (b) θ = -20° / 20°; (c) θ = -30° / 30°; (d) θ = -60° / 0°; (e) θ = -30° / 0° / 30°; (f) θ = -60° / -30° / 0°;

[0066] Figure 19 Beam gain diagrams corresponding to different multi-beam pointing directions, (a) θ = -10° / 10°; (b) θ = -20° / 20°; (c) θ = -30° / 30°; (d) θ = -60° / 0°; (e) θ = -30° / 0° / 30°; (f) θ = -60° / -30° / 0°; S11 parameter diagrams corresponding to different multi-beam pointing directions, (a) θ = -10° / 10°; (b) θ = -20° / 20°; (c) θ = -30° / 30°; (d) θ = -60° / 0°; (e) θ = -30° / 0° / 30°; (f) θ = -60° / -30° / 0°;

[0067] Figure 20 Antenna gain diagrams corresponding to different multi-beam pointing directions, (a) θ = -10° / 10°; (b) θ = -20° / 20°; (c) θ = -30° / 30°; (d) θ = -60° / 0°; (e) θ = -30° / 0° / 30°; (f) θ = -60° / -30° / 0°; (b) (c) (d)

[0068] Figure 21 Flowchart diagram provided for an embodiment of the present application. DETAILED DESCRIPTION

[0069] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application.

[0070] Examples of the embodiments are shown in the drawings, in which the same or similar symbols represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, but cannot be understood as a limitation of the present application.

[0071] Embodiment one

[0072] One embodiment of the present application provides a two-dimensional antenna array multi-beam scanning method based on holographic amplitude weighting, referring to Figure 21 as shown, comprising:

[0073] Step S1: determining the position information of each radiating unit in the two-dimensional antenna array, including calculating the unit spacing and arrangement mode;

[0074] In one specific embodiment of the present application, in step S1, the two-dimensional antenna array comprises:

[0075] a plurality of periodically arranged radiating units, each radiating unit comprising a complementary open resonant ring slot structure and a liquid crystal layer;

[0076] a center feeding structure for providing a reference wave to the radiating units;

[0077] a control module for generating an encoding sequence and regulating the excitation amplitude of each radiating unit through the encoding sequence.

[0078] Step S2: generating the amplitude weighting value of each radiating unit according to the target wave direction, using two-dimensional multi-beam holographic amplitude weighting technology, the amplitude weighting value of the radiating unit is determined by two-dimensional multi-beam holographic amplitude weighting technology;

[0079] In one specific embodiment of the present application, in step S2, the amplitude weighting value is determined by the following method:

[0080] On the basis of the existing one-dimensional leaky-wave antenna single / multi-beam scanning method and two-dimensional leaky-wave antenna single-beam scanning method based on holographic amplitude weighting, a two-dimensional array multi-beam scanning holographic amplitude weighting technology is proposed;

[0081] generating a holographic pattern based on the interference effect of the reference wave and the target wave;

[0082] solving the problem of beam center depression existing in the two-dimensional array, and correcting the phase of the holographic pattern;

[0083] determining a contribution rate of each radiating element to a target beam pointing through the holographic pattern;

[0084] discretizing the contribution rate to obtain a binary discretized encoding sequence.

[0085] In one embodiment of the present application, the reference wave is determined according to a central feed structure, and the target wave is determined according to an intended beam pointing.

[0086] In one embodiment of the present application, the target wave, the holographic pattern and the amplitude weighting function are determined according to the following formula:

[0087]

[0088] wherein y n represents a longitudinal coordinate of the nth radiating element relative to the excitation source, x m represents a transverse coordinate of the mth radiating element relative to the excitation source, k ref represents a propagation constant of the reference wave in the transmission medium, k0 represents a propagation constant in free space at the same frequency, and θ0 represents a target beam elevation angle pointing, represents a target beam horizontal angle pointing.

[0089] In one embodiment of the present application, the target wave and the amplitude weighting function are determined according to the following formula:

[0090]

[0091]

[0092] wherein y n represents a longitudinal coordinate of the nth radiating element relative to the excitation source, x m represents a transverse coordinate of the mth radiating element relative to the excitation source, k0 represents a propagation constant in free space at the same frequency, and θ g represents a beam pointing of the gth elevation angle, represents a beam pointing of the tth horizontal angle, G represents a number of target beam elevation angles, T represents a number of target beam horizontal angles, g represents the gth target elevation angle, and t represents the tth target horizontal angle.

[0093] Step S3: generating a corresponding binary discretized encoding sequence based on the amplitude weighting values to control the excitation amplitude of each radiating element;

[0094] In one embodiment of the present application, in step S3, the holographic antenna principle and the amplitude weighting technique are combined, and the excitation amplitude of each element is weighted and controlled to realize the beam scanning function of the two-dimensional leaky-wave antenna array.

[0095] In one specific embodiment of the present application, in step S3, the two-dimensional leaky-wave antenna array respectively adopts a continuous amplitude-weighted excitation amplitude function and a discrete amplitude-weighted excitation amplitude function.

[0096] In one specific embodiment of the present application, the continuous amplitude-weighted excitation amplitude function is determined according to the following formula after solving the problem of beam center depression:

[0097]

[0098] wherein k ref represents the propagation constant of the reference wave in the transmission medium, k0 represents the propagation constant in free space at the same frequency, θ g represents the beam pointing of the gth elevation angle, represents the beam pointing of the tth horizontal angle, G represents the number of target beam elevation angles, T represents the number of target beam horizontal angles, g represents the gth target elevation angle, and t represents the tth target horizontal angle.

[0099] In one specific embodiment of the present application, the discrete amplitude-weighted excitation amplitude function is determined according to the following formula:

[0100]

[0101] wherein θ g represents the beam pointing of the gth elevation angle, represents the beam pointing of the tth horizontal angle.

[0102] Step S4: Design a Ka-band liquid-crystal-based two-dimensional holographic beam scanning leaky-wave antenna square array, and control the radiation pattern of the two-dimensional antenna array through the coding sequence to realize multi-beam scanning.

[0103] Embodiment Two

[0104] In one embodiment provided by the present application, the holographic antenna can form a holographic pattern by adjusting the unit amplitude or phase to achieve the expected beam scanning. There are mainly two methods to form the holographic pattern at present: one is to jointly adjust the amplitude and phase, and to control the spatial switching of the beam by a phase shifter and adjusting the unit excitation amplitude, but this method has a complex structure and high cost. The other is to fix the phase distribution, and to control the beam forming and switching only by adjusting the unit excitation amplitude, and this method has a simple structure, low cost and easy integration. Therefore, in order to realize the beam scanning function of the leaky-wave antenna, an amplitude weighting method is adopted, which is based on the principle of the holographic antenna and is a holographic antenna technology only by adjusting the unit excitation amplitude, and is therefore also called holographic amplitude weighting technology or amplitude weighting technology based on the holographic principle. The holographic antenna mainly includes a source antenna and a holographic structure, the source antenna outputs a reference wave, and the expected beam required is a target wave. The function of the holographic antenna is to generate a holographic image to record the information of the target wave, and the target wave can be restored by irradiating the holographic image with the reference wave. In terms of the structure of the one-dimensional leaky-wave antenna, the expression forms of the reference wave and the target wave equations are:

[0105] ψ ref (y n )=exp(-jk ref y n ) (1)

[0106] ψ obj (y n ,θ0)=exp(-jk0sin(θ0)y n ) (2)

[0107] Wherein, y n represents the distance between the nth radiation unit and the excitation source, k ref represents the propagation constant of the reference wave in the transmission medium, k0 represents the propagation constant in free space at the same frequency, and θ0 represents the expected beam pointing.

[0108] The interference pattern ψ(y n ,θ0) can be obtained from the interference principle:

[0109]

[0110] When the reference wave source ψ ref (y n ) irradiates the holographic image, the last term in equation (3) can be used to reproduce the target wave:

[0111]

[0112] ψ obj (y n ,θ0)=ψ inf (y n, θ0) ψ ref (y n ) / |ψ ref (y n )| 2 (5)

[0113] Holographic amplitude weighting technique is a technique for forming a holographic pattern by setting an amplitude function to regulate the excitation amplitude of each unit, which can be expressed as:

[0114]

[0115] From formula (6), the contribution rate m(y n , θ0) of each antenna unit to the expected beam pointing θ0 can be obtained. The contribution rate is a number between 0 and 1, and the greater the value, the closer the phase shift value at y n to the target phase shift value, the more energy y n radiates, and the greater the contribution of the unit to the expected beam direction; otherwise, the contribution is smaller. Discretize the amplitude function: when m(y n , θ0) is greater than 0.5, set it to “1”; when m(y n , θ0) is less than or equal to 0.5, set it to “0”. The unit excitation amplitude after processing can be expressed as:

[0116]

[0117] From formula (7), the corresponding binary discrete encoding sequence of the expected beam pointing can be obtained, and this holographic amplitude weighting technique based on binary weighting can be expressed as: Figure 2 .

[0118] The holographic structure is constructed by weighting the unit amplitude to realize beam control, and this holographic amplitude weighting technique can be explained by the theory of array antenna far-field pattern. A one-dimensional array antenna is set, which is composed of N units with a spacing of d, and the phase of each unit increases by a fixed value ξ. The far-field region of the nth unit is:

[0119]

[0120] is the directional diagram function of the antenna unit, I n and ξ n are the amplitude and phase of the nth unit. The far-field approximation of formula (8) is: n ≈1 / r. The total field expression of the array antenna in the far zone is:

[0121]

[0122] where Δr = r - r n = ndsinφ, φ represents the intended beam pointing. The far-field radiation pattern of the array antenna is:

[0123]

[0124] where the array factor expression is:

[0125]

[0126] Given the known antenna element radiation characteristics, the antenna pattern study can be reduced to the study of the antenna array factor. The phase of the holographic antenna element is determined by the distance of the element from the excitation source and the propagation constant of the reference wave in the medium, i.e. -k ref nd. Therefore, the array factor of the holographic antenna can be expressed as:

[0127]

[0128] According to equation (12), as long as the amplitude weighting value m(nd, φ) at each element is determined using the holographic amplitude weighting technique, the target beam can be obtained.

[0129] The one-dimensional array multi-beam scanning implementation method based on holographic amplitude weighting is introduced as follows:

[0130] Multi-beam antennas can simultaneously communicate in multiple directions, thereby achieving more efficient data transmission and more stable signal reception. The beam scanning method based on the principle of holographic antennas can not only control a single beam, but also achieve one-dimensional or two-dimensional spatial multi-beam scanning. When there are two or more target beam pointing directions, the one-dimensional multi-beam scanning based on holographic amplitude weighting needs to modify equations (2) and (6). The modified target beam equation and amplitude function are represented as:

[0131]

[0132] where θ g represents the gth beam pointing direction. Equation (14) represents the amplitude function when continuous amplitude weighting is performed, which can be further binarized to obtain the amplitude function when discrete amplitude weighting is performed, as shown in equation (15).

[0133]

[0134] For a two-dimensional holographic beam scanning leaky-wave antenna, the antenna bottom feed method is used in the design, i.e. a feed source is added at a specific position under the two-dimensional array. Figure 3A two-dimensional array structure is shown in which each grid node represents an independent radiating element. The reference wave propagates from the bottom feed to the periphery of the antenna, and each element radiates energy to free space according to the specified weighting value of the target beam when passing through the element.

[0135] In order to realize the beam scanning function of the two-dimensional leaky-wave antenna array, the excitation amplitude of each element needs to be weighted and controlled in combination with the holographic antenna principle and amplitude weighting technology. Different two-dimensional planar holographic structures can record different holographic patterns, and different antenna patterns can be obtained by exciting these holographic structures with reference waves. This two-dimensional spatial beam scanning method based on holographic amplitude weighting technology can be explained by the radiation pattern synthesis theory of two-dimensional planar array antennas.

[0136] Specifically, the radiation pattern of a rectangular planar antenna array containing N x ×N y elements is placed on the xy plane, and a coordinate system is established as Figure 4 .

[0137] Let the adjacent matrix grid row spacing be d x , the column spacing be d y , and the coordinate position and position vector of the mnth element P mn be as shown in equations (16) and (17):

[0138]

[0139] Let the distance from the coordinate origin to a point in the far field region be r, and the unit vector be:

[0140]

[0141] Let the mnth element excitation current be Its far field region can be expressed as:

[0142]

[0143] In the formula, H (θ, φ) represents the radiation element pattern function. In the far field radiation, the amplitude in equation (19) can be approximated as 1 / R mn ≈1 / r.

[0144] Figure 4 The far field region of the mnth element can be calculated as: Then the far field region of the mnth element is:

[0145]

[0146] The total far field region of the entire array and its array factor are as shown in equations (21) and (22):

[0147]

[0148] Assume the excitation current is distributed by column as distributed by row as then

[0149]

[0150] In formula (23), I xm and I yn are the amplitude distribution of the linear array in x and y direction respectively; ξ x and ξ y are the progressive phase of the linear array in x and y direction respectively. The amplitude expression M((md x ,nd y ),(θ,φ)) is used to express I xm I yn , so the array factor expression of the far field of the two-dimensional planar antenna array is:

[0151]

[0152] The reference wave in the two-dimensional antenna array is transmitted from the center feed to the periphery along the transmission medium, and when the wave passes through the elements arranged periodically on the two-dimensional plane, it radiates energy to the free space. In order to construct the holographic pattern, the amplitude weighting technique can be used to determine the appropriate weighted amplitude value M((md x ,nd y ) for each position (md x ,nd y ) of the element.

[0153] Based on the one-dimensional beam scanning formula, the beam scanning formula in two-dimensional space is obtained, the reference wave (formula (1)) is changed to the form of formula (25), and the target wave (formula (2)) is changed to the form of formula (26). Where x m , y n represent the position information of the recording point on the holographic structure, m represents the mth column in the x-axis direction, n represents the nth column in the y-axis direction, θ0, represents a certain angle pointing in two-dimensional space. The two-dimensional holographic distribution pattern can be represented by (27):

[0154]

[0155] According to formulas (25), (26) and (27), the element excitation amplitude functions of the two-dimensional leaky-wave antenna array when using continuous amplitude weighting and discrete amplitude weighting respectively can be obtained. The amplitude function when using continuous amplitude weighting is shown in formula (28), and the amplitude function when using discrete amplitude weighting is shown in formula (29).

[0156]

[0157] In the design of two-dimensional antenna array, if the center feeding method is adopted, it will cause the phase inconsistency of forward wave and backward wave, and then cause the far field radiation difference of antenna front and back wave, which will produce the problem of beam center depression. Therefore, the above two-dimensional holographic leaky-wave antenna single beam scanning theory needs to be modified for the beam depression problem caused by center feeding. Assuming that the antenna is in y polarization direction, the forward wave and backward wave of the antenna are propagated along the positive and negative axes of y in the three-dimensional coordinate system, then the xoz plane is taken as the boundary, and the surface of the antenna is divided into two parts, which are xoy(left) and xoy(right) respectively. When the phase difference of the two planes reaches 180°, the beam center depression problem can be solved. For the two-dimensional holographic distribution formulas (27), (28) and (29), after setting the phase difference of the two planes to 180°, the new holographic distribution formulas are shown in (30), (31) and (32):

[0158]

[0159] The above is for one-dimensional antenna array, based on the holographic amplitude weighted leaky-wave antenna single beam and multi-beam scanning theory, and is extended to two-dimensional array based on one-dimensional array, which describes the two-dimensional leaky-wave antenna array single beam scanning method based on holographic amplitude weighting. Based on the existing beam scanning theory based on holographic amplitude weighting, the application proposes a two-dimensional leaky-wave antenna multi-beam scanning method based on holographic amplitude weighting.

[0160] For the realization of two-dimensional leaky-wave antenna multi-beam, referring to the multi-beam formula of one-dimensional array, the target wave function and amplitude function of two-dimensional leaky-wave antenna multi-beam can be obtained by combining formulas (13), (14), (27), (28) and (29) as follows:

[0161]

[0162] Where, θ g represents the gth elevation angle (Theta) beam pointing, g θ t represents the tth horizontal angle (Phi) beam pointing.

[0163] According to formula (34), further binary processing is carried out, and the continuous amplitude weighting is converted into discrete amplitude weighting, as shown in formula (35).

[0164]

[0165] Here, referring to two-dimensional single beam scanning, the above two-dimensional multi-beam method is modified considering the beam center depression problem, and formula (34) is modified to formula (36) as follows.

[0166] ​

[0167] According to formula (36), further binarization processing is performed to convert the continuous amplitude weighting into discrete amplitude weighting, as shown in formula (37).

[0168]

[0169] The design and simulation of a Ka-band liquid crystal-based two-dimensional holographic leaky-wave antenna array includes unit structure design and simulation. The antenna unit adopts a microstrip line model based on a complementary split resonant ring (CSRR) slot unit. The CSRR is a complementary form of an SRR. The SRR structure is derived from the development of artificial electromagnetic materials. The structure is composed of two concentric metal split rings. In the leaky-wave antenna, the frequency selectivity can be achieved by embedding the SRR structure into the antenna leaky slot structure. The device design based on the SRR structure not only has the advantages of simple structure and miniaturization, but also has good high-frequency resonance characteristics. In this way, the CSRR also has the characteristics of negative magnetic permeability. The CSRR slot unit has more adjustable size variables and more complex slot structures than the SRR structure, which is conducive to optimizing the design of the structure unit and can more flexibly control the electromagnetic field radiation efficiency and the energy leaked into the free space. Figure 5 The two-dimensional leaky-wave antenna array unit structure includes a copper metal ground plate, a transmission medium, a microstrip line based on a CSRR slot unit, and a liquid crystal layer. The transmission medium is made of Rogers 4003 material with a relative dielectric constant of 3.55 and a loss tangent angle of 0.0027. A 0.035 mm thick copper plate is placed at the bottom of the transmission medium as a ground layer. The microstrip line based on the CSRR slot unit is made of 2 um thick copper, and the top has a 0.2 mm thick liquid crystal layer. The liquid crystal material is of GT3-23001 type. This type of liquid crystal has a wide tuning range, and the relative dielectric constant can be switched from 2.5 to 3.3. The corresponding loss angle tangent can be switched from 0.0143 to 0.0038. The detailed size of the antenna unit is shown in Table 1.

[0170] Table 1 Antenna size parameters

[0171]

[0172] The S11 and S21 parameters of the two-dimensional leaky-wave antenna unit based on the CSRR slot unit are simulated. By changing the relative dielectric constant of the liquid crystal material, the resonator resonance frequency can be changed. At different frequency points, the radiation power and impedance matching performance of the antenna are different.

[0173] From Figure 6It can be concluded that when the relative permittivity of the liquid crystal is 2.5, the antenna has a significant resonance characteristic at 32.1 GHz, at which time 2.5 can be encoded as "1" and 3.3 can be encoded as "0". At the same time, the corresponding S11 parameter at this frequency is below -10 dB, indicating that the antenna unit has good impedance matching performance. Figure 7 The electric field and magnetic field energy distribution at the CSRR gap is shown, and from the figure it can be concluded that the electric field energy is mainly distributed at the left and right opening resonant rings of the CSRR gap, and the magnetic field is mainly distributed on the upper and lower sides of the outer circle of the gap. The microstrip line model based on the CSRR gap unit can effectively radiate electromagnetic wave energy.

[0174] The 400 antenna units are arranged in a two-dimensional plane in a periodic manner. According to the periodic leaky-wave antenna transmission principle, the unit spacing has a great influence on the radiation characteristics of the antenna. The unit spacing is set as a scanning parameter. Through a series of comparative simulation experiments, it is found that when the element spacing is too large, the 20x20 holographic leaky-wave antenna array is prone to produce high-order harmonics; when the spacing is too small, the coupling effect between the units is increased, resulting in poor beam scanning performance. Therefore, after optimization design, the unit and unit spacing is finally confirmed to be 3.55mm, and the overall length and width of the antenna are both 70.95mm, as shown in FIG. 8(a) and FIG. 8(b).

[0175] The entire antenna array is fed by a coaxial feeding method, and the feeding port is located at the center of the array. As shown in FIG. 8(b), the probe length in the medium is 2.35mm, in which h t is 1.45mm, and h c is 0.9mm. The coaxial probe radius w t is 0.8mm, the coaxial dielectric material is selected as Teflon, and the diameter w c is 4.4mm. By placing the wave-absorbing material around the transmission medium, the reflected wave can be reduced.

[0176] If a two-dimensional leaky-wave antenna array single-beam scanning simulation is to be realized, the working frequency is set to 32.1GHz, and a two-dimensional leaky-wave antenna array composed of 400 units is simulated. The array expected beam pointing is set to ( θ=0°), and the discrete amplitude weighting coding sequence is obtained by entering it into equations (28) and (29). The holographic pattern corresponding to the sequence is shown in FIG. 9, in which the red squares represent the relative permittivity of the liquid crystal layer being 2.5, and the blue area represents 3.3. Based on this holographic distribution state, the modeling simulation in HFSS obtains the far-field pattern as shown in FIG. 10. Figure 9 Figure 10

[0177] As shown in FIG. 11, the holographic pattern corresponding to the sequence is shown in FIG. 12, in which the red squares represent the relative permittivity of the liquid crystal layer being 2.5, and the blue area represents 3.3. Based on this holographic distribution state, the modeling simulation in HFSS obtains the far-field pattern as shown in FIG. 13. Figure 10 ​​As shown, when the expected direction is (0°, 0°), the actual direction at θ = 0° results in a beam dip problem, which is caused by the inconsistency in the phase of the front and rear waves due to the center feeding method. To address the beam dip problem in the two-dimensional holographic distribution formula (27), a new holographic distribution formula is obtained by setting a 180° phase difference between the two planes. Substituting the expected beam direction back into formulas (30), (31), and (32), the modified holographic distribution of the antenna surface and the far-field pattern are obtained as follows: Figure 11 and Figure 12 As shown, the problem of beam center concavity has been resolved.

[0178] Pick θ can be taken as 0° / -30° / 30° / -60° / 40° respectively. Figure 13 for The antenna holographic distribution diagrams corresponding to each beam pointing to the time are shown. The relative permittivity of the liquid crystal material corresponding to "0" is 3.3 (blue block), and the relative permittivity of the liquid crystal material corresponding to "1" is 2.5 (red block). Figure 14 Gain diagrams for different beam orientations.

[0179] Figure 15 The S11 parameters for each beam pointing direction are shown. At a frequency of 32.1 GHz, the S11 parameters are all below -9 dB, and generally below -10 dB, indicating good impedance matching. From... Figure 15 It can be concluded that different beam directions are consistent with expectations. Table 2 shows the specific angle error and main beam gain for different beam directions.

[0180] Now, regarding multi-beam scanning, combined with the proposed two-dimensional holographic multi-beam method, we take... θ takes values ​​of -10° / 10°, -20° / 20°, -30° / 30°, -60° / 0°, -30° / 0° / 30°, and -60° / -30° / 0° respectively. Substituting these values ​​into formulas (36) and (37) yields the corresponding “0 / 1” encoding sequences. Figure 17 for Holographic distribution of antenna arrays corresponding to different multi-beam pointing directions at different times. Figure 18 Gain diagrams for different multi-beam pointing methods.

[0181] Figure 19 Showing Figure 18 The S11 parameters corresponding to each multi-beam pointing mode are all below -9dB at 32.1GHz, and are basically below -10dB, indicating good impedance matching.

[0182] from Figure 18It can be concluded that the different beam pointing directions are consistent with the expectation. Table 3 is the specific angle error and main beam gain when the different multi-beam pointing directions, the pointing error is within 2.2°, and the beam gain is within 9dB, realizing the multi-beam switching of the array and verifying the effectiveness of the proposed amplitude-weighted two-dimensional holographic leaky-wave antenna multi-beam scanning method.

[0183] Figure 20 In the case of (a), when , the array realizes its double-beam / three-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.6°, and the beam gain is within 9dB, up to 10.55dB. In the case of (b), when , the array realizes its double-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.5°, and the beam gain is up to 10.57dB, within 3dB. In the case of (c), when , the array realizes its double-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.9°, and the beam gain is up to 10.74dB. In the case of (d), when

[0184] , the array realizes its double-beam / three-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.5°, and the beam gain is up to 10.60dB. Figure 20

[0185] Figure 20 In the case of (a), when , the array realizes its double-beam / three-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.6°, and the beam gain is within 9dB, up to 10.55dB. In the case of (b), when , the array realizes its double-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.5°, and the beam gain is up to 10.57dB, within 3dB. In the case of (c), when , the array realizes its double-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.9°, and the beam gain is up to 10.74dB. In the case of (d), when

[0186] , the array realizes its double-beam / three-beam scanning with the elevation angle θ from -30° to 30°, the pointing error is within 2.5°, and the beam gain is up to 10.60dB. Figure 20

[0187] From the experimental results of Figures 17 to 20 , it can be concluded that the antenna array can realize its beam azimuth angle ​​The dual / three-beam scanning from -30° to 30° in the azimuth angle and from -60° to 30° in the elevation angle shows that the designed two-dimensional antenna array can not only realize single-beam scanning, but also realize multi-beam scanning, and it is verified that the proposed two-dimensional antenna array multi-beam scanning method based on holographic amplitude weighting can be well applied to the design and application of two-dimensional leaky-wave antenna arrays.

[0188] The above merely provides a detailed description of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

[0189] Each of the embodiments in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The embodiments of the present application are described with reference to flowcharts and / or block diagrams of the method, terminal device (system), and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks can be realized by computer program instructions. These computer program instructions can be provided to the processor of the general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device realize the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The apparatus for realizing the functions specified in one block or multiple blocks. These computer program instructions can also be stored in the computer readable storage medium which can guide the computer or other programmable data processing terminal device to work in a specific way, so that the instructions stored in the computer readable storage medium generate the manufactured product including the instruction apparatus, which realizes the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The apparatus for realizing the functions specified in one block or multiple blocks. These computer program instructions can also be loaded into the computer or other programmable data processing terminal device, so that a series of operation steps are performed on the computer or other programmable terminal device to generate the computer-implemented process, so that the instructions executed on the computer or other programmable terminal device provide the means for realizing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1The steps of the functions specified in one or more boxes. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the invention. Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0190] The methods and apparatus provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0191] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "a specific embodiment" or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0192] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A holographic amplitude weighted based two-dimensional antenna array multi-beam scanning method, characterized in that, The application relates to a Ka-band liquid-crystal-based two-dimensional holographic beam scanning leaky-wave antenna array. The application comprises the following steps: Step S1: determining the position information of each radiating unit in the two-dimensional antenna array, including unit spacing and arrangement mode; Step S2: generating the amplitude weighting value of each radiating unit according to a target wave direction, and utilizing a two-dimensional multi-beam holographic amplitude weighting technology, wherein the amplitude weighting value of the radiating unit is determined by the two-dimensional multi-beam holographic amplitude weighting technology; Step S3: generating a corresponding binary discretization coding sequence based on the amplitude weighting value to control the excitation amplitude of each radiating unit; 2. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 1, characterized in that, Step S4: designing a Ka-band liquid-crystal-based two-dimensional holographic beam scanning leaky-wave antenna array, and adjusting the radiation pattern of the two-dimensional antenna array through the coding sequence to realize multi-beam scanning. In step S1, the two-dimensional antenna array comprises: A plurality of periodically arranged radiating units, each of which comprises a complementary open resonant ring slot structure and a liquid crystal layer; A center feeding structure for providing a reference wave to the radiating units; 3. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 1, characterized in that, A control module for generating a coding sequence and adjusting the excitation amplitude of each radiating unit through the coding sequence. In step S2, the amplitude weighting value is determined by the following method: Generating a holographic pattern based on the interference effect of the reference wave and the target wave; Correcting the phase of the holographic pattern by solving the beam center depression problem existing in the two-dimensional array; Determining the contribution rate of each radiating unit to the target beam direction through the holographic pattern; 4. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 3, characterized in that, Discretizing the contribution rate to obtain a binary discretization coding sequence.

5. The hologram amplitude weighted based two-dimensional antenna array single beam scanning method according to claim 3, characterized in that, The reference wave is determined according to the center feeding structure, and the target wave is determined according to the expected beam direction. where y n represents the longitudinal coordinate of the nthradiating element with respect to the excitation source, x m represents the transverse coordinate of the mthradiating element with respect to the excitation source, k ref represents the propagation constant of the reference wave in the transmission medium, k0represents the propagation constant in free space at the same frequency, and θ0represents the target beam elevation angle pointing, represents the target beam horizontal angle pointing.

6. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 3, characterized in that, The target wave, the holographic pattern and the amplitude weighting function are determined according to the following formula: where y n represents the longitudinal coordinate of the nthradiating element with respect to the excitation source, x m represents the transverse coordinate of the mthradiating element with respect to the excitation source, k0represents the propagation constant in free space at the same frequency, θ g represents the beam pointing of the gthelevation angle, represents the beam pointing of the tthorizontal angle, G represents the number of target beam elevation angles, T represents the number of target beam horizontal angles, g represents the gthtarget elevation angle, and t represents the tthorizontal angle.

7. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 1, characterized in that, The target wave and the amplitude weighting function are determined according to the following formula:

8. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 7, characterized in that, In step S3, the beam scanning function of the two-dimensional leaky-wave antenna array is realized by weighting and adjusting the excitation amplitude of each radiating unit through the holographic antenna principle and the amplitude weighting technology.

9. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 8, characterized in that, In step S3, the two-dimensional leaky-wave antenna array respectively adopts a continuous amplitude weighting excitation amplitude function and a discrete amplitude weighting excitation amplitude function. where k ref represents the propagation constant of the reference wave in the transmission medium, k0represents the propagation constant in free space at the same frequency, θ g represents the beam pointing of the gth elevation angle, represents the beam pointing of the tth horizontal angle, G represents the number of target beam elevation angles, T represents the number of target beam horizontal angles, g represents the gth target elevation angle, and t represents the tth target horizontal angle.

10. The hologram amplitude weighted based two-dimensional antenna array multi-beam scanning method according to claim 8, characterized in that, The continuous amplitude weighting excitation amplitude function is determined according to the following formula after solving the beam center depression problem: The discrete amplitude weighting excitation amplitude function is determined according to the following formula: where θ g denotes the beam pointing of the g-th elevation angle, denotes the beam pointing of the t-th horizontal angle.

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