A holographic phase coding-based liquid crystal phased array dynamic star-seeking control method

Abstract

The application relates to a holographic phase coding-based liquid crystal phased array dynamic satellite searching control method, which acquires an expected beam pointing angle of a target satellite relative to an antenna array; generates a two-dimensional phase matrix suitable for a liquid crystal phased array based on the expected beam pointing angle; performs temperature compensation on the two-dimensional phase matrix and converts the two-dimensional phase matrix into digital driving levels, which are loaded to a liquid crystal driving circuit; forms a radio frequency beam pointing to the expected beam pointing angle through a liquid crystal phased array antenna panel; and detects a beam pointing error in real time according to a downlink signal characteristic and performs compensation. The holographic phase coding-based liquid crystal phased array dynamic satellite searching control method exhibits significant technical progress and practical advantages in multiple aspects; the method constructs a high-performance and high-reliability dynamic beam pointing system through key technologies such as holographic phase coding, real-time temperature compensation, high-speed calculation and closed-loop feedback, and is particularly suitable for high-dynamic scenes such as high-speed mobile carriers and low-orbit satellite communication.

Description

A Dynamic Star-Finding Control Method for Liquid Crystal Phased Array Based on Holographic Phase Encoding Technical Field

[0001] This invention relates to the field of optoelectronic information technology, and more specifically, to a dynamic star-finding control method for liquid crystal phased arrays based on holographic phase coding. Background Technology

[0002] With the booming development of the global satellite communication industry, especially the rapid deployment of low Earth orbit (LEO) satellite constellations, unprecedentedly stringent requirements have been placed on the dynamic beam pointing capability of ground terminal antennas. Traditional mechanical rotating antennas, due to their inherent defects such as large size, high power consumption, slow response, and high maintenance costs, are no longer suitable for the needs of high-speed mobile vehicles and high-dynamic satellite tracking scenarios. Against this backdrop, electronically scanned phased array antennas, as a solution with no inertia and high agility, have gradually become the mainstream direction of technological development. In particular, liquid crystal phased array antenna technology, which has significant advantages in terms of cost, power consumption, and integration, can achieve continuous and precise control of electromagnetic wave phase in the radio frequency / microwave band due to its unique electric field tunable dielectric anisotropy characteristics. This provides a highly promising technical approach for realizing low-cost, low-power, planar dynamic satellite-finding systems, showing broad application prospects in mobile satellite communication fields such as vehicle-mounted, airborne, and shipborne systems.

[0003] Specifically, the tunable dielectric constant exhibited by liquid crystal materials in the radio frequency / microwave band is the core physical basis for constructing liquid crystal phased array antennas. By precisely applying an external voltage, the orientation state of liquid crystal molecules can be effectively controlled, thereby changing their equivalent refractive index and ultimately achieving continuous modulation of the phase delay of electromagnetic waves passing through the medium. This voltage-controlled passive phase shift mechanism, compared to traditional ferrite, MEMS, or gallium arsenide (GaAs) semiconductor phase shifters, not only has significant advantages in material cost but also greatly reduces the complexity and power consumption of its driving circuit. Thanks to its inherent planar structure, liquid crystal phased array antennas can be more easily integrated into various mobile platforms, effectively avoiding the system complexity and reliability challenges caused by the high integration density and heat dissipation problems of traditional phased array antennas. Therefore, liquid crystal phased array technology is considered a highly attractive and feasible technical route in the field of dynamic satellite search, especially in applications with strict limitations on cost, power consumption, and size. It can achieve rapid beam scanning and precise tracking in a purely electronic manner, significantly improving the stability and reliability of communication links.

[0004] However, with the continuous development of related technologies and the increasingly stringent performance requirements of high-dynamic satellite communication scenarios, some inherent characteristics of the aforementioned liquid crystal phased array technology at the principle level have gradually revealed its deep limitations and inherent contradictions when facing new challenges. In particular, how to quickly and accurately generate control holograms and overcome the challenges of response time and loss in the radio frequency field of liquid crystal devices is crucial to realizing a high-performance dynamic satellite-finding system. Applying it to dynamic, high-precision satellite tracking faces several key challenges:

[0005] Real-time phase calculation: The high relative speed of satellites requires extremely high beam update rates (e.g., tens to hundreds of times per second), which poses a severe challenge to the real-time calculation capability of phase maps.

[0006] Environmental adaptability: Temperature changes can affect the dielectric constant and response speed of liquid crystal materials, leading to phase control errors.

[0007] Broadband performance: Satellite communication links may require a certain operating bandwidth, and the dispersion characteristics of liquid crystal phased arrays may cause the beam to shift with frequency.

[0008] Therefore, how to construct a dynamic satellite-finding control method for liquid crystal phased arrays that can effectively solve the above-mentioned deep technical contradictions and achieve high speed, high precision, high robustness and broadband performance has become a key challenge and a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0009] This invention aims to solve the deep technical contradictions faced by existing liquid crystal phased array dynamic satellite tracking technology. To achieve the above-mentioned objective, this invention provides a liquid crystal phased array dynamic satellite tracking control method based on holographic phase coding. The method can achieve high-speed, high-precision, and inertia-free dynamic satellite tracking control, and at the same time provides a phased array antenna system with compact structure, low power consumption, and controllable cost.

[0010] This invention provides a dynamic star-finding control method for a liquid crystal phased array based on holographic phase encoding, comprising the following steps:

[0011] Step 1: Obtain the desired beam pointing angle of the target satellite relative to the antenna array;

[0012] Step 2: Perform dynamic holographic phase map calculation and optimization, and generate a two-dimensional phase matrix suitable for liquid crystal phased array based on the desired beam pointing angle;

[0013] Step 3: Perform temperature compensation and encoding loading of the phase diagram, perform temperature compensation on the two-dimensional phase matrix and convert it into digital driving level, and load it into the liquid crystal driving circuit;

[0014] Step 4: Perform radio frequency beamforming and transmission, and radiate a radio frequency beam pointing to the desired beam pointing angle through the liquid crystal phased array antenna panel;

[0015] Step 5: Implement closed-loop feedback and dynamic disturbance suppression, and detect and compensate for beam pointing error in real time based on downlink signal characteristics.

[0016] Preferably, the specific steps of step 1 are as follows:

[0017] Acquire external input information, which includes real-time satellite orbit ephemeris;

[0018] Acquire its own state information, which includes local geographic location information and carrier attitude information;

[0019] Obtain system error calibration data pre-stored in non-volatile memory, the system error calibration data including array panel mounting error and channel inconsistency calibration parameters;

[0020] Transform the satellite's position in the first coordinate system to the second coordinate system with the antenna phase center as the origin;

[0021] Based on the carrier attitude information, the desired beam vector is transformed from the platform coordinate system to the panel coordinate system of the antenna array;

[0022] The system error calibration data is superimposed on the calculated original pointing angle as an angle compensation amount, and the azimuth and elevation angles of the target satellite relative to the antenna are calculated in real time. The azimuth and elevation angles are then used to determine the final desired beam pointing angle.

[0023] Preferably, step 2 specifically involves: based on the desired beam pointing angle... A two-dimensional phase matrix is ​​generated for all elements of the array; a phase winding operation is performed on the two-dimensional phase matrix to normalize the phase values ​​to a preset phase tuning range; phase-amplitude joint optimization is performed to iteratively optimize the phase distribution to achieve sidelobe suppression, multi-beam generation or null formation of far-field pattern characteristics, and finally an optimized holographic phase map is generated.

[0024] Preferably, the method for generating the two-dimensional phase matrix is ​​as follows: firstly, an initial reference phase is defined for all elements of the array. Where k is a coefficient set according to the operating wavelength λ or array size; according to the desired beam pointing angle Calculate the directional compensation phase of each element of the array relative to the initial reference phase. The direction-compensated phase is then superimposed onto the initial reference phase to obtain a two-dimensional phase matrix. Wherein, the direction compensation phase The expression is: Where dx and dy are the spacing between array cells in the x and y directions, respectively, and λ is the operating wavelength.

[0025] Preferably, the phase winding operation includes: winding the two-dimensional phase matrix... The folded phase is generated by folding the phase to a preset range of [-π, π] using the arctangent function. ; for the folded phase Compensation is performed to adjust it to the range of [0, 2π] to accommodate the characteristic of liquid crystal devices that provide a maximum 2π phase tuning capability; if ,but ;otherwise, .

[0026] Preferably, the phase-amplitude joint optimization includes:

[0027] Sidelobe suppression: Introducing an amplitude weighting function The transmit / receive amplitudes of different array elements are weighted to reduce sidelobe levels and improve anti-interference capability; the complex excitation coefficient of each element is determined as follows: ,in Subsequently, an iterative Fourier transform algorithm is used to optimize the phase distribution Φ while maintaining the beam pointing direction, so that the resulting far-field pattern satisfies both the main lobe pointing direction and has low sidelobe characteristics; this process generates the optimized holographic phase pattern. ;

[0028] Multi-beam generation: If it is necessary to track K target satellites simultaneously, the corresponding phase map Φ_k is calculated for each target; then, the K phase maps are superimposed to generate a multi-beam phase map. , where A_k is the amplitude weight of the k-th beam; the multi-beam phase map Φ_sum is the final loaded phase map.

[0029] Preferably, step 3 specifically involves: monitoring the operating temperature T of the liquid crystal phased array panel in real time using a temperature sensor; querying a pre-stored "voltage-phase-temperature" lookup table in the memory to correct the optimized holographic phase diagram, thereby compensating for the drift of the liquid crystal dielectric constant caused by temperature changes and maintaining phase control accuracy; quantizing the corrected continuous phase diagram into Q discrete levels to generate a digital driving level matrix D(i,j); loading the digital driving level matrix D(i,j) into the liquid crystal driving circuit through a high-speed digital interface, wherein the liquid crystal driving circuit generates a corresponding analog voltage matrix and applies it to each unit of the liquid crystal phased array.

[0030] Preferably, step 4 specifically comprises: generating a carrier signal through a radio frequency signal source; uniformly feeding the carrier signal into each radiating element of the liquid crystal phased array through a power divider network; integrating an independently addressable liquid crystal unit, which, under the driving voltage applied by the liquid crystal driving circuit, generates a phase delay on the passing radio frequency signal; and coherently superimposing the radio frequency signals emitted by all radiating elements in space to form a pointing angle towards the desired beam. Sharp radio frequency beam.

[0031] Preferably, step 5 specifically involves: monitoring the intensity indication of the received signal or estimating the beam pointing error using a single-pulse angle measurement method. ; to the beam pointing error The data is fed into a PID controller to fine-tune the desired beam pointing angle to compensate for low-frequency disturbances. Dynamic disturbance suppression also includes: transforming the platform's high-frequency angular vibration data into a coordinate-inverted compensation phase map, and then superimposing it on the optimized holographic phase map in real time to achieve instantaneous cancellation of high-frequency disturbances.

[0032] Preferably, the PID controller is a proportional-integral-derivative controller, whose output is used to form an outer loop feedback loop for the desired beam pointing angle; high-frequency angular vibration data is measured by an IMU; coordinate transformation converts the platform attitude angular velocity output by the IMU into a beam pointing correction amount in the antenna array panel coordinate system. The inverted compensation phase map is calculated by directly multiplying the high-frequency vibration component of the platform attitude by a negative coefficient and performing coordinate transformation, quickly calculating the phase amount that needs to be compensated for each array element, and then digitally superimposing it with the main holographic phase map in real time. This is then loaded into the liquid crystal driving circuit in the next frame phase update cycle, thereby canceling the influence of platform vibration on beam pointing in real time at the radio frequency level.

[0033] The technical effects and advantages of this invention are as follows: Through key technologies such as holographic phase coding, real-time temperature compensation, high-speed computing and closed-loop feedback, a high-performance and highly reliable dynamic beam pointing system is constructed, which is particularly suitable for high-dynamic scenarios such as high-speed mobile carriers and low-orbit satellite communications.

[0034] It achieves millisecond-level beam switching and pointing adjustment, which is far superior to the response time of traditional mechanical antennas. At the same time, its beam tracking accuracy is high, which effectively improves the stability of the communication link and the data transmission efficiency, and meets the stringent requirements for continuous and stable tracking of high-speed moving targets.

[0035] It has excellent high-frequency disturbance suppression capability. By integrating an inertial measurement unit (IMU) and adopting an anti-phase real-time compensation mechanism, it can effectively counteract beam offset caused by carrier vibration.

[0036] The use of a fully planar liquid crystal phased array architecture without mechanical moving parts not only significantly reduces the size and weight of the system, but also significantly reduces power consumption, which is beneficial for integration and application on mobile platforms such as vehicles and airborne systems. Attached Figure Description

[0037] Figure 1 is a flowchart of the dynamic satellite search control method of the present invention;

[0038] Figure 2 is a schematic diagram of a dynamic star-finding control system for a liquid crystal phased array based on holographic phase coding;

[0039] Figure 3 is a schematic diagram of a single-pulse feedback principle. Detailed Implementation

[0040] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0041] In a specific embodiment, as shown in Figure 1, the dynamic star-finding control method for liquid crystal phased arrays based on holographic phase encoding includes the following engineering steps:

[0042] The first step is to perform target trajectory prediction and desired beam angle calculation. This step accurately obtains the desired beam pointing angle of the target satellite relative to the antenna array.

[0043] The second step is to perform dynamic holographic phase map calculation and optimization, and generate a two-dimensional phase matrix suitable for liquid crystal phased array based on the above-mentioned desired beam pointing angle. This matrix is ​​precisely optimized to meet the requirements of radio frequency beam characteristics. The third step is to perform temperature compensation and encoding loading of the phase map, perform real-time temperature compensation on the two-dimensional phase matrix, convert it into a high-precision digital drive level, and then load it into the liquid crystal drive circuit.

[0044] Fourth step: Perform radio frequency beamforming and transmission, and radiate a radio frequency beam pointing to the desired beam pointing angle through the liquid crystal phased array antenna panel;

[0045] Step 5: Implement closed-loop feedback and dynamic disturbance suppression. Based on the characteristics of the downlink signal, detect the beam pointing error in real time and compensate according to the error type to maintain the accuracy and stability of beam pointing.

[0046] In a preferred embodiment of the present invention, the first step, "target trajectory prediction and desired beam angle calculation," is performed by a trajectory prediction module deployed within the main controller. This module first acquires multi-source external input information, primarily satellite orbit ephemeris data obtained in real-time from external network services. This information is transmitted via a network interface, such as an integrated cellular data module (e.g., a Sierra Wireless HL7800 series module based on 5G NR or LTE Cat-M1 standards) or a standard gigabit Ethernet interface, to communicate between the data link layer and the network layer, receiving satellite position and velocity vector data predicted by high-precision SGP4 or J2 perturbation models. Simultaneously, it acquires its own status information, including local geographic location information provided by a high-performance GNSS module (e.g., a u-blox F9P module supporting multiple constellations like BDS / GPS / GLONASS / Galileo), and raw data from a three-axis gyroscope, three-axis accelerometer, and three-axis magnetometer provided by an inertial measurement unit (IMU). The raw IMU data is processed by an attitude fusion algorithm deployed on the main controller, such as an extended Kalman filter (EKF) or a quaternion-based complementary filter algorithm, to output carrier attitude parameters such as roll angle, pitch angle, and yaw angle at high frequencies (e.g., 200 Hz). In addition, the module also accesses system error calibration data pre-stored in non-volatile memory (e.g., industrial-grade NAND Flash, typically with a capacity of 4GB to 16GB). This data covers physical errors generated during the installation of the antenna array panel and phase mismatch calibration parameters caused by inherent inconsistencies between RF channels. These parameters are acquired and stored using professional measurement equipment (such as vector network analyzers and near-field probes) during initial system deployment or periodic maintenance.

[0047] Specifically, the coordinate transformation module within the trajectory prediction module is responsible for transforming the satellite's position in the first coordinate system (e.g., geocentric inertial coordinate system J2000 ECI or geocentric Earth-Fixed coordinate system ITRF ECEF) obtained from ephemeris data to a second coordinate system with the antenna phase center as the origin, namely the local northeast-sky (ENU) coordinate system. This transformation involves multi-step matrix operations and geodetic algorithms, including Earth rotation correction, latitude, longitude, and altitude transformation from an oblate spheroid model to Cartesian coordinates, and coordinate system transformation based on the local tangent plane. Subsequently, combined with the real-time attitude information provided by the IMU, the attitude compensation module accurately transforms the desired beam vector from the platform's instantaneous attitude coordinate system to the fixed coordinate system of the antenna array panel. For example, if the platform yaws, pitches, or rolls, the desired pointing vector needs to be multiplied by the inverse of the rotation matrix corresponding to the quaternion obtained from the attitude calculation, thereby ensuring that the beam always points to the target's relative position on the antenna panel. Finally, the error superposition module uses pre-calibrated system errors (such as a 0.5-degree beam pointing error caused by array unit installation position deviation or a phase mismatch of up to 10 degrees between RF channels) as angle compensation values, superimposing them in real time onto the calculated original pointing angle. These compensation values ​​can be expressed as Δθ_error and They are related to the originally calculated azimuth angle θ_raw and pitch angle. Superimposed to determine the final desired beam pointing angle. = θ_raw + Δθ_error, This angle precisely corrects for inherent system errors, improving overall pointing accuracy. The main controller typically employs a high-performance embedded microprocessor unit, such as the NXP i.MX8M Plus or NVIDIA Jetson Xavier NX, which runs a Linux operating system and executes high-level application algorithms written in C++ / Python, ensuring that complex computational tasks can be completed with low latency.

[0048] The second step, "Dynamic Holographic Phase Map Calculation and Optimization," is primarily executed by a high-speed computing unit, typically a high-performance field-programmable gate array (FPGA), such as the Xilinx Versal AI Core VC1902 or an Intel Agilex 7 I-Series FPGA. First, based on the desired beam pointing angle... Generate a two-dimensional phase matrix for all elements in the array. In practice, this is achieved by first defining an initial reference phase.

[0049] ;

[0050] Where i and j are the row and column indices of the array element, and the coefficient k is set according to the operating wavelength λ and the array size. For example, for a Ku-band 256x256 array, k can be 0.01π / λ; subsequently, based on the desired beam pointing angle... The directional compensation phase ΔΦ(i,j) of each element in the array relative to the reference phase is calculated and superimposed on the initial reference phase to obtain the two-dimensional phase matrix. The calculation of the directional compensation phase ΔΦ(i,j) strictly follows the electromagnetic wave path difference principle, and its expression is:

[0051] ;

[0052] Where dx and dy represent the spacing of the array elements in the x and y directions, respectively. For example, for a Ku-band antenna operating at 12.5 GHz, dx and dy can be designed to be 0.8λ, which is about 19.2 mm; λ is the operating wavelength, for example, 24 mm.

[0053] Subsequently, a phase winding operation is performed on the two-dimensional phase matrix. This operation aims to normalize the continuously varying phase values ​​to the tunable physical range of the liquid crystal device. Specifically, the two-dimensional phase matrix is ​​wound using an arctangent function. Folding to a preset range of [-π, π] generates a folded phase. This function can correctly handle phase values ​​that cross the 2π boundary. Next, the folded phase... Compensation is performed to adjust it to the range of [0, 2π] to accommodate the physical characteristic of liquid crystal devices that provide a maximum phase tuning capability of 360 degrees (i.e., 2π). The specific rule is: if... <0, then ;otherwise, ; This indicates the winding phase angle; this process ensures that all phase values ​​are within the positive tuning range, avoiding control ambiguity.

[0054] Next, phase-amplitude joint optimization is performed; this optimization process aims to iteratively optimize the phase distribution to achieve far-field pattern characteristics, such as sidelobe suppression, multi-beam generation, or null formation.

[0055] For sidelobe suppression, this invention introduces an amplitude weighting function W(i,j) to weight the transmit or receive amplitudes of different array elements, thereby reducing sidelobe levels and improving antenna anti-interference capability. The amplitude weighting function W(i,j) can be selected from Taylor or Chebyshev distributions; for example, a Taylor weighting function can be used for a 40 dB sidelobe attenuation requirement. The complex excitation coefficients of each element are determined as follows: ,in ;

[0056] Subsequently, an Iterative Fourier Transform (IFT) algorithm, such as the Gerchberg-Saxton algorithm or the Yang-Gu algorithm, is employed to iteratively optimize the phase distribution under the strong constraint of keeping the main lobe pointing unchanged. This algorithm typically iterates alternately between the Fourier and spatial domains. Each iteration applies the desired pattern constraints (e.g., main lobe width, side lobe level) in the Fourier domain and the phase constraints (e.g., 0 to 2π) in the spatial domain, gradually converging to the optimal solution. This iterative process usually reaches the convergence criterion (e.g., mean square error less than 10^-4) within 50 to 200 iterations, ultimately generating the optimized holographic phase map. .

[0057] For multi-beam generation, if it is necessary to track K target satellites simultaneously, the single-beam phase map Φ_k corresponding to each target is calculated independently; then, the K phase maps are superimposed to generate a multi-beam phase map. , where A_k is the amplitude weight of the k-th beam, used to control the relative intensity of each beam; the multi-beam phase map Φ_sum is the final loaded phase map.

[0058] In a preferred embodiment of the present invention, the third step, "temperature compensation and encoding loading of the phase map," precisely corrects and transforms the optimized holographic phase map. This step first uses a high-precision temperature sensor (e.g., several PT1000 resistance thermometers attached to the center and edges of the liquid crystal phased array panel, or an Analog Devices ADT7420 digital temperature sensor with integrated digital output, achieving a measurement accuracy of ±0.1℃ and a response time of less than 100ms) to monitor the operating temperature T of the liquid crystal phased array panel in real time. Subsequently, the main controller queries a "voltage-phase-temperature" lookup table pre-stored in non-volatile memory to correct the optimized holographic phase map Φopt. This lookup table is constructed by accurately measuring the phase response characteristics of the liquid crystal at different temperatures and driving voltages using specialized optical equipment (such as a Michelson interferometer or polarimeter) in a laboratory environment, thereby constructing a three-dimensional data matrix. Its input parameters are the desired phase value (e.g., 256 discrete values ​​from 0 to 2π) and the current temperature value (e.g., discrete temperature points from -40℃ to 85℃), and the output is the corresponding required driving voltage value. The correction process typically employs bilinear interpolation or cubic spline interpolation algorithms to ensure that accurate driving voltage values ​​can be obtained at any real-time temperature point and desired phase point, thereby compensating for the drift of the liquid crystal dielectric constant caused by temperature changes and its impact on phase control accuracy.

[0059] The corrected continuous phase map is then quantized into Q discrete levels. For example, to achieve a phase resolution of 0.1 degrees within a 2π phase range, a 10-bit or 12-bit quantization precision is typically used, i.e., Q = 1024 or 4096 levels, thereby generating a digital drive level matrix D(i, j). This quantization process maps the continuous analog phase requirement to discrete voltage steps that the liquid crystal driving circuit can generate. The digital drive level matrix D(i, j) is rapidly and in parallel loaded into the liquid crystal driving circuit via a high-speed digital interface (e.g., a mini_LVDS interface or a MIPI DSI interface with data transfer rates up to several Gbps and low electromagnetic interference characteristics). The liquid crystal driving circuit includes multiple high-precision digital-to-analog converter (DAC) arrays (e.g., TIDAC5681 or ADI AD9783), each providing hundreds of channels. The output of each DAC array is amplified by a voltage amplifier (e.g., ADIADA4898) to provide accurate and stable analog drive voltages to each unit of the liquid crystal phased array. The driving voltage range is typically designed to be between 0V and 5V, and it has a fast response capability of less than 10 microseconds to ensure the instantaneous nature of phase loading.

[0060] In the fourth step, "RF Beamforming and Transmission," the RF signal source, a high-performance RF transceiver module, first generates a carrier signal. This module integrates a digitally controlled oscillator (NCO), mixer, low-noise amplifier (LNA), power amplifier (PA), and digital frequency converter, capable of generating carrier signals operating in the Ku band (e.g., 12 GHz to 18 GHz) or Ka band (e.g., 26 GHz to 40 GHz) with frequency stability better than 10^-8. The carrier signal is then uniformly fed into each radiating element of the liquid crystal phased array through a power divider network (e.g., a Wilkinson power divider array integrated on a multilayer dielectric substrate, a Butler matrix, or a tree-shaped feed network). This power divider network is carefully designed to ensure that the amplitude consistency at each port is better than ±0.5 dB and the phase consistency is better than ±5 degrees during signal transmission, thereby avoiding the impact of uneven signal distribution on beamforming accuracy.

[0061] The liquid crystal phased array antenna panel consists of hundreds to thousands of individual liquid crystal cells mounted on a microwave dielectric substrate (e.g., Rogers RO4003C or RO3003 material, featuring low-loss tangent and a stable dielectric constant). Each radiating element is typically a microstrip patch antenna, its size and shape (e.g., square or circular patch) optimized using electromagnetic simulation software (e.g., Ansys HFSS or CST Studio Suite) to achieve a radiation efficiency greater than 90% and a return loss less than -15 dB at the operating frequency. Above each radiating element is an independently addressable liquid crystal cell containing a narrow liquid crystal cavity filled with a nematic liquid crystal material (e.g., Merck MLC-7036) and held by a pair of transparent conductive electrodes (typically indium tin oxide, ITO); these electrodes conduct electricity to apply the driving voltage while ensuring low-loss transmission of the RF signal. Under the independent driving voltage applied by the liquid crystal driving circuit, the average orientation angle of the liquid crystal molecules changes continuously, thereby modulating the equivalent refractive index of the electromagnetic wave passing through the liquid crystal cavity. This change in refractive index directly results in a precise phase delay in the radio frequency (RF) signal. By precisely controlling the phase delay of each liquid crystal cell, the RF signals emitted by all radiating cells are coherently superimposed in space with a phase relationship, thereby forming a pointing angle towards the desired beam. A sharp radio frequency beam. The phase tuning range of the liquid crystal cell is at least 360 degrees (2π), and the phase modulation accuracy is better than 10 degrees over the entire operating temperature range to ensure accurate beam pointing.

[0062] The fifth step, "Closed-Loop Feedback and Dynamic Disturbance Suppression," ensures the continuous accuracy and stability of beam pointing. This step first performs error detection, which is done by monitoring the Received Signal Strength Indicator (RSSI) or by using a single-pulse angle measurement method to estimate the beam pointing error. The preferred error detection scheme is a single-pulse angle measurement method, which forms a sum beam (Σ) and a difference beam by partitioning the liquid crystal phased array panel. For example, referring to Figure 3, the antenna array is divided into four quadrants. By performing amplitude weighting and phase combination on the received signals in each quadrant, a sum beam Σ with maximum receiving gain is formed, along with two difference beams Δθ and Δφ (corresponding to the elevation and azimuth directions, respectively) with zero points in the zero-error direction. By comparing the amplitude and phase of the received signals from the sum beam and the difference beam, the downlink signal processing unit (usually a DSP or FPGA) calculates the beam pointing error with high precision. This method can complete angle measurement within a single pulse cycle, exhibiting extremely high real-time performance.

[0063] Furthermore, dynamic disturbance suppression is implemented: for low-frequency disturbances, such as satellite orbit prediction residuals (typically less than 0.1 degrees / second) and slow platform drift (e.g., attitude changes of 0.5 degrees / minute due to carrier fuel consumption or wind effects), the beam pointing error... The data is fed into a finely tuned PID controller (parameters Kp=0.8, Ki=0.05, Kd=0.01). This PID controller fine-tunes the desired beam pointing angle, and its output is directly fed back to the desired beam angle in the first step, forming an outer loop feedback loop to achieve gradual compensation for low-frequency errors. Furthermore, this invention also provides instantaneous cancellation of high-frequency disturbances. The IMU (e.g., ADI ADIS16470 or Bosch BMI270) provides angular rate and attitude information in high-frequency bandwidth, enabling direct measurement of rapid angular vibration data of the platform in the frequency range of tens to hundreds of hertz (e.g., road bumps during vehicle travel or fuselage shaking caused by aircraft vortices, with angular acceleration reaching hundreds of degrees / second^2). The high-frequency angular vibration data of the platform output by the IMU is transformed into coordinates to quickly generate an inverted compensated phase diagram. This inverse phase compensation map calculates the phase compensation required for each array element in real time by multiplying the high-frequency vibration components of the platform attitude (such as angular velocity or angular acceleration) by a preset negative coefficient and performing a rotation transformation from the carrier coordinate system to the antenna panel coordinate system. Subsequently, this compensation phase map is digitally superimposed in real time with the optimized holographic phase map Φopt and loaded into the liquid crystal driving circuit within the next phase update cycle (e.g., 1 millisecond). This mechanism can instantly cancel the instantaneous offset of beam pointing caused by the platform's high-frequency vibration at the radio frequency level, thereby maintaining extremely high beam pointing stability.

[0064] The specific single-pulse angle measurement method is as follows:

[0065] First, the liquid crystal phased array antenna array is divided into four quadrant subarrays, defined as: upper left (A), upper right (B), lower left (C), and lower right (D). Let x(i,j) be the complex baseband digital signal received by the (i,j)-th element in the array after liquid crystal phase modulation and down-conversion. According to the amplitude weighting function W(i,j), the composite complex signal of each subarray... , , , The calculation is as follows:

[0066]

[0067] Where Q ∈{A, B, C, D} represents the four quadrant regions;

[0068] Then: using the principle of single-pulse amplitude ratio angle measurement, the beam pointing error is proportional to the ratio of the difference signal and the sum of the signals. By calculating the normalized error voltage, the specific angle deviation can be calculated.

[0069] Azimuth error estimate δAz:

[0070]

[0071] Pitch angle error estimate δEL:

[0072]

[0073] Where Re(·) represents taking the real part of the complex number, and the in-phase / out-of-phase characteristics of the sum beam and the difference beam are used to determine the deviation direction (positive / negative). The slope of the single-pulse angle discrimination is a constant determined by the beamwidth of the antenna array. Complex addition and subtraction operations are performed on the signals of the four subarrays in the digital domain to construct the sum beam (Σ), azimuth difference beam (ΔAz), and elevation difference beam (ΔEL).

[0074] Sum Beam (Σ): Represents the direction of maximum gain of the main lobe of the entire array, used for signal demodulation and as a phase reference;

[0075]

[0076] Azimuth difference beam ( ): Formed by the signal difference between the left and right subarrays, which produces a zero depth when the beam points to the center;

[0077]

[0078] Pitch difference beam (ΔEL): formed by the signal difference between the upper and lower subarrays;

[0079] .

[0080] As shown in Figure 2, the present invention also provides a dynamic satellite-finding control system for a liquid crystal phased array based on holographic phase coding. The system is physically and functionally divided into three subsystems: a control subsystem, a radio frequency subsystem, and a feedback subsystem. The control subsystem is responsible for calculating and issuing phase control signals. Its core components include: a trajectory prediction module, which is a high-performance main controller, such as an embedded computing platform equipped with an ARM Cortex-A72 architecture processor (2.0 GHz) and running a real-time operating system. It has 16GB DDR4 RAM and 64GB eMMC storage, used to run high-level algorithms such as trajectory prediction, coordinate transformation, and attitude fusion, and to interact with external interfaces; a holographic phase calculation module, which is a high-speed computing unit, usually an FPGA, such as a Xilinx Zynq UltraScale+ MPSoC, which integrates a holographic phase calculation IP core. This IP core adopts a multi-stage pipeline and parallel processing architecture, and can complete the calculation and optimization of complex holographic phase maps containing tens of thousands of array units in less than 1 millisecond; and system memory, including high-speed volatile memory (such as DDR4 SDRAM) as the working memory of the FPGA and the main controller, and non-volatile memory (such as NAND). Flash and EEPROM are used to store system firmware, calibration data, and critical voltage-phase-temperature lookup tables. Finally, there is the LCD driving circuit, which contains multiple multi-channel, high-resolution (e.g., 12-bit) digital-to-analog converter (DAC) arrays capable of generating precise analog voltage signals and independently applying the driving voltage to each cell of the LCD phased array via a high-speed differential transmission interface, ensuring the instantaneous and stable phase loading. The feedback processing module, a downlink signal processing unit implemented by a DSP or FPGA, is responsible for demodulating, filtering, and power detection (for RSSI) of the received downlink RF signal from the feedback subsystem, and executing a single-pulse angle measurement algorithm to accurately calculate beam pointing error. This unit supports high-speed data acquisition and real-time signal processing, ensuring the response speed of the feedback loop.

[0081] The radio frequency (RF) subsystem is responsible for generating RF signals and radiating them after phase modulation using a liquid crystal phased array. Its core components include: a high-performance RF transceiver, such as the ADI ADRV9009 or Analog Devices HMC7044, capable of generating low-phase-noise Ku or Ka-band carrier signals, and equipped with a high-linearity transmit power amplifier (PA) and low-noise receive amplifier (LNA), as well as a high-speed ADC / DAC, enabling comprehensive signal processing from baseband to RF. A power divider / combiner network is also included, optimized for array size and operating frequency. For example, for large arrays, a multi-layer dielectric substrate integrated microstrip power divider or a complex tree-shaped feed network can be used to ensure uniform distribution and collection of RF energy among array elements, minimizing insertion loss and phase mismatch. Finally, the liquid crystal phased array antenna panel is the core radiating and receiving component of this system. The panel typically consists of 1024x1024 individual liquid crystal cells, each containing an optimized microstrip patch radiator, a cavity filled with nematic liquid crystal material, and a transparent ITO electrode. The panel features broadband performance (e.g., bandwidth up to 1 GHz in the Ku band) and low loss characteristics, and precisely modulates the phase of the transmitted radio frequency signal by electrically controlling the orientation of liquid crystal molecules.

[0082] The feedback subsystem is responsible for monitoring beam alignment and providing error signals. Its main components include: an inertial measurement unit (IMU) employing high-precision MEMS inertial sensors, such as the STMicroelectronics ASM330LHH or TDK InvenSense ICM-42688-P, which provides data from a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetometer, with an update rate up to 800 Hz. The output attitude and angular rate information is used for high-frequency vibration compensation. Finally, there is a temperature sensor, such as the Maxim Integrated MAX31889 high-precision temperature sensor with integrated digital output. Its temperature probe is directly attached to multiple key areas of the LCD panel, monitoring the panel temperature in real time and transmitting data to the control subsystem via I2C or SPI interfaces. The measurement range covers -55℃ to +125℃, with an accuracy of ±0.25℃.

[0083] In one specific embodiment, the system described in this invention is applied to a low Earth orbit (LEO) satellite communication ground terminal operating in the Ku band. The liquid crystal phased array consists of eight independent subarray modules, each with 32x32 radiating elements, totaling 8192 independently controllable phase-shifting elements. The spacing between each radiating element is 0.65λ to avoid grating lobe effects. The high-speed computing unit uses a Xilinx Versal AI Core VC1902 SoC FPGA, whose integrated holographic phase calculation IP core employs a highly parallelized custom ALU array and a deep pipeline design, enabling it to complete the calculation of an optimized phase map containing 256 levels of Taylor weighting (40dB sidelobe attenuation) within 0.4 milliseconds, with a power consumption of approximately 15 watts. The feedback subsystem employs a single-pulse angle measurement scheme. By implementing sum and difference beam generation and complex signal comparison algorithms within the FPGA, combined with a high sampling rate ADC, it achieves a beam tracking accuracy of 0.08 degrees (RMS) for LEO satellites, meaning a beam pointing error of less than 0.08 degrees at 12.5 GHz. The entire system can maintain a beam switching delay of less than 5 milliseconds and a stable communication link on high-speed moving platforms, such as high-speed trains or unmanned vehicles. The total system power consumption in continuous operation mode is approximately 120 watts, representing an 80% reduction in size and a 70% reduction in weight compared to traditional mechanical satellite-finding systems.

[0084] Comparative Example

[0085] To clearly illustrate the technical advantages and non-obviousness of this invention, we introduce a typical prior art solution as a comparative example for analysis. This comparative example is a traditional mechanical Ku-band satellite tracking antenna system driven by a stepper motor or servo motor. Its core beam pointing control relies on physically rotating the antenna reflector or feed source, and uses GPS receivers to obtain the carrier position, inertial measurement units (IMUs) to provide attitude information, and ephemeris data for open-loop or low-speed closed-loop control. This mechanical system typically includes a dual-axis turntable (azimuth and pitch axes), driven by two high-precision servo motors, with a high-resolution encoder for angle feedback. Its control logic is implemented through a motion controller based on a microcontroller (such as an ARM Cortex-M series), receiving the desired pointing command from the host computer and controlling the servo motors to rotate and change the antenna's physical pointing. For beamforming, it uses a fixed parabolic reflector, achieving gain through its geometry, but lacks dynamic beamforming capabilities. In the feedback loop, the system typically performs simple peak tracking by monitoring the received signal strength (RSSI), but the response speed is limited by mechanical inertia.

[0086] Table 1: Differences in key performance indicators between the liquid crystal phased array dynamic star-finding control system based on holographic phase encoding of this invention and the mechanical comparative model.

[0087]

[0088] As shown in Table 1, the dynamic satellite acquisition control method and system based on holographic phase coding for liquid crystal phased arrays exhibit significant technical advantages in several key performance indicators, including beam switching delay, tracking accuracy, high dynamic disturbance suppression, power consumption, size and weight, lifespan, and multi-beam capability. Mechanical tracking antennas, due to their inherent mechanical inertia, cannot meet the requirements of real-time, high-bandwidth communication in terms of beam switching delay and tracking accuracy when facing high-speed moving targets such as LEO satellites. Their bulky size and high power consumption also limit their widespread application on mobile platforms. This invention overcomes the physical limitations of traditional mechanical systems by introducing holographic phase coding, high-speed FPGA computing, real-time temperature compensation, and a multi-level closed-loop feedback mechanism. It also effectively solves the technical challenges posed by the characteristics of liquid crystal materials, thereby achieving stable and high-precision communication for LEO satellites under extreme dynamic environments, fully demonstrating the non-obviousness and innovation of this invention.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A dynamic star-finding control method for a liquid crystal phased array based on holographic phase encoding, characterized in that, Includes the following steps: Step Step 1: Obtain the desired beam pointing angle of the target satellite relative to the antenna array; Step 2: Perform dynamic holographic phase map calculation and optimization, and generate a two-dimensional phase matrix suitable for the liquid crystal phased array based on the desired beam pointing angle; Specifically, generate a two-dimensional phase matrix for all elements of the array based on the desired beam pointing angle, where the desired beam pointing angle is... Step 3: Perform phase winding operation on the two-dimensional phase matrix to normalize the phase value to a preset phase tuning range; perform phase-amplitude joint optimization to iteratively optimize the phase distribution to achieve sidelobe suppression, multi-beam generation, or null formation of far-field pattern characteristics, and finally generate an optimized holographic phase map; Step 4: Perform temperature compensation and encoding loading of the phase map, perform temperature compensation on the two-dimensional phase matrix and convert it to digital driving level, and load it to the liquid crystal driving circuit; The specific steps are: monitor the working temperature T of the liquid crystal phased array panel in real time through a temperature sensor; query the "voltage-phase-temperature" lookup table stored in the memory to correct the optimized holographic phase map, thereby compensating for the liquid crystal dielectric constant drift caused by temperature changes to maintain phase control accuracy; The corrected continuous phase map is quantized into Q discrete levels, thereby generating a digital drive level matrix D(i,j); The digital driving level matrix D(i,j) is loaded into the liquid crystal driving circuit through a high-speed digital interface. The liquid crystal driving circuit generates a corresponding analog voltage matrix and applies it to each unit of the liquid crystal phased array. Step 4: Perform radio frequency beamforming and transmission, and radiate a radio frequency beam pointing to the desired beam pointing angle through the liquid crystal phased array antenna panel. Step 5: Perform closed-loop feedback and dynamic disturbance suppression, and detect and compensate for beam pointing error in real time according to the downlink signal characteristics.

2. The dynamic star-finding control method for liquid crystal phased array based on holographic phase encoding according to claim 1, characterized in that: The specific steps of step 1 are as follows: acquiring external input information, which includes real-time satellite orbit ephemeris; acquiring self-state information, which includes local geographical location information and carrier attitude information; The system error calibration data, which includes array panel installation error and channel inconsistency calibration parameters, is pre-stored in non-volatile memory. The satellite's position in the first coordinate system is transformed to a second coordinate system with the antenna phase center as the origin. Combined with the carrier attitude information, the desired beam vector is transformed from the platform coordinate system to the antenna array panel coordinate system. The system error calibration data is superimposed on the calculated original pointing angle as an angle compensation amount. The azimuth and elevation angles of the target satellite relative to the antenna are calculated in real time. The azimuth and elevation angles are used to determine the final desired beam pointing angle.

3. The dynamic star-finding control method for liquid crystal phased array based on holographic phase encoding according to claim 1, characterized in that: The method for generating the two-dimensional phase matrix is ​​as follows: First, an initial reference phase is defined for all elements of the array. Where k is a coefficient set according to the operating wavelength λ or array size; according to the desired beam pointing angle Calculate the directional compensation phase of each element of the array relative to the initial reference phase. The direction-compensated phase is then superimposed onto the initial reference phase to obtain a two-dimensional phase matrix. Wherein, the direction compensation phase The expression is: Where dx and dy are the spacing between array cells in the x and y directions, respectively, and λ is the operating wavelength.

4. The dynamic star-finding control method for a liquid crystal phased array based on holographic phase encoding according to claim 3, characterized in that: The phase winding operation includes: wrapping the two-dimensional phase matrix... The folded phase is generated by folding the phase to a preset range of [-π, π] using the arctangent function. ; for the folded phase Compensation is performed to adjust it to the range of [0, 2π] to accommodate the characteristic of liquid crystal devices that provide a maximum 2π phase tuning capability; if ,but ;otherwise, ， This indicates the winding phase angle.

5. The dynamic star-finding control method for a liquid crystal phased array based on holographic phase encoding according to claim 4, characterized in that: The phase-amplitude joint optimization includes: sidelobe suppression: introducing an amplitude weighting function. The transmit / receive amplitudes of different array elements are weighted to reduce sidelobe levels and improve anti-interference capability; the complex excitation coefficient of each element is determined as follows: ,in Subsequently, an iterative Fourier transform algorithm is used to optimize the phase distribution Φ while maintaining the beam pointing direction, so that the resulting far-field pattern satisfies both the main lobe pointing direction and has low sidelobe characteristics; this process generates the optimized holographic phase pattern. Multi-beam generation: If it is necessary to track K target satellites simultaneously, calculate the corresponding phase map Φ_k for each target; then, superimpose the K phase maps to generate a multi-beam phase map. Where A_k is the amplitude weight of the k-th beam; the multi-beam phase map Φ_sum is the final loaded phase map. This indicates taking the phase angle.

6. The dynamic star-finding control method for a liquid crystal phased array based on holographic phase encoding according to claim 1, characterized in that: The specific steps of step 4 are as follows: a carrier signal is generated by a radio frequency signal source; the carrier signal is uniformly fed into each radiating element of the liquid crystal phased array through a power divider network; each radiating element integrates an independently addressable liquid crystal unit, which, under the driving voltage applied by the liquid crystal driving circuit, generates a phase delay on the passing radio frequency signal; the radio frequency signals emitted by all radiating elements are coherently superimposed in space, thereby forming a pointing angle towards the desired beam. Sharp radio frequency beam.

7. The dynamic star-finding control method for liquid crystal phased array based on holographic phase encoding according to claim 1, characterized in that: The specific steps of step 5 are as follows: monitor the intensity indication of the received signal or estimate the beam pointing error (Δθ, Δφ) by using a single-pulse angle measurement method; send the beam pointing error (Δθ, Δφ) to the PID controller to fine-tune the desired beam pointing angle to compensate for low-frequency disturbances; dynamic disturbance suppression also includes: after transforming the platform's high-frequency angular vibration data into coordinates, generating an inverted compensation phase map, and then superimposing it on the optimized holographic phase map in real time and loading it to achieve instantaneous cancellation of high-frequency disturbances.

8. The dynamic star-finding control method for a liquid crystal phased array based on holographic phase encoding according to claim 7, characterized in that: The PID controller is a proportional-integral-derivative controller, whose output is used to form an outer loop feedback loop for the desired beam pointing angle; high-frequency angular vibration data is measured by an IMU; coordinate transformation converts the platform attitude angular velocity output by the IMU into a beam pointing correction amount in the antenna array panel coordinate system; the inverted compensation phase map is calculated by directly multiplying the high-frequency vibration component of the platform attitude by a negative coefficient and performing coordinate transformation, calculating the phase amount that each array element needs to compensate, and then digitally superimposing it with the main holographic phase map in real time. It is then loaded into the liquid crystal driving circuit in the next frame phase update cycle, thereby canceling the influence of platform vibration on beam pointing in real time at the radio frequency level.

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