FPGA-based liquid crystal phased array system

Abstract

This invention discloses an FPGA-based liquid crystal phased array system, belonging to the field of satellite communication technology. It includes: an ARM processor for performing coordinate transformation between the satellite's theoretical pointing angle and the carrier's attitude angle to obtain the target beam pointing angle and generate a target beam pointing command; an FPGA beam control module for performing real-time integration calculations on inertial measurement data to obtain the carrier's attitude angle; executing a search task to calculate the beam pointing according to the target beam pointing command; and executing a tracking task to calculate the beam pointing error and dynamically adjust the beam pointing when the AGC signal exceeds a threshold; a liquid crystal phased array antenna for driving the liquid crystal phased array antenna to form a beam and radiate the beam towards the satellite; and an RF link for obtaining the AGC signal and feeding it back to the FPGA beam control module, obtaining the transmit signal, and sending it to the liquid crystal phased array antenna. This invention can solve the problems of complex control links, redundant test architecture, and losses introduced by DC blockers.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and in particular to an FPGA-based liquid crystal phased array system. Background Technology

[0002] The existing technical solution generally involves the signal sequentially passing through the radio frequency (RF) output port of a vector network analyzer, a first RF DC blocker, a liquid crystal phase shifter, a second RF DC blocker, and the RF input port of the vector network analyzer. The first RF DC blocker blocks the DC component, allowing only the RF signal to pass. The liquid crystal phase shifter adjusts the phase of the RF signal by changing the arrangement of liquid crystal molecules using an applied voltage. The second RF DC blocker further blocks the DC component, ensuring signal purity. The RF input port of the vector network analyzer receives the phase-shifted RF signal and performs phase / amplitude measurements.

[0003] In existing technologies, phase adjustment control of liquid crystal phase shifters often relies on independent analog voltage regulation modules or simple microcontrollers, lacking a unified high-speed processing unit for the generation and transmission of control signals. Taking a single-channel or few-channel liquid crystal phased array system as an example, its control flow is typically as follows: the target phase value is manually set, and then the signal passes sequentially through the microcontroller, the digital-to-analog converter (DAC), and the control terminal of the liquid crystal phase shifter; whereby the microcontroller is used to convert the phase value into a corresponding analog voltage signal; and the control terminal of the liquid crystal phase shifter is used to realize phase adjustment.

[0004] However, for multi-channel liquid crystal phased array systems, the existing control schemes have obvious limitations: the control signals for each channel are generated by decentralized circuits, making it difficult to ensure the synchronization of phase adjustment between multiple channels; and the microcontroller has limited computing speed and cannot process complex phase optimization algorithms in real time, resulting in slow beam scanning speed and low pointing accuracy of the system.

[0005] Furthermore, existing technologies typically use low-speed serial interfaces between the control module and the liquid crystal phase shifter, resulting in significant data transmission delays that further limit the system's dynamic response performance. Additionally, existing technologies do not provide real-time compensation for the temperature drift of the liquid crystal phased array. When the ambient temperature changes, the dielectric constant of the liquid crystal molecules alters, leading to increased phase adjustment errors and impacting system stability. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an FPGA-based liquid crystal phased array system that can form a closed-loop control system for BeiDou positioning, theoretical pointing calculation, search and capture, scanning and tracking, and AGC signal feedback correction, thereby solving the problems of complex control links, redundant test architecture, and losses introduced by DC blockers.

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0008] This invention provides an FPGA-based liquid crystal phased array system, including a main controller, a liquid crystal phased array antenna, and a radio frequency link. The main controller integrates an ARM processor and an FPGA wave control module.

[0009] The ARM processor is used to receive carrier position information and carrier attitude angle sent by the FPGA beam control module. Based on the preset low-orbit satellite two-line orbital element ephemeris data and carrier position information, it calculates the satellite theoretical pointing angle, performs coordinate transformation between the satellite theoretical pointing angle and the carrier attitude angle to obtain the target beam pointing angle, generates a target beam pointing command based on the target beam pointing angle, and sends the target beam pointing command to the FPGA beam control module.

[0010] The FPGA beam control module is used to receive inertial measurement data, target beam pointing instructions sent by the ARM processor, and AGC signals sent by the RF link. It performs real-time integration calculation on the inertial measurement data to obtain the carrier attitude angle and sends the carrier attitude angle to the ARM processor. According to the target beam pointing instructions, it executes a search task to calculate the beam pointing. When the AGC signal exceeds a threshold, it executes a tracking task to calculate the beam pointing error and dynamically adjusts the beam pointing. The beam pointing is then sent to the liquid crystal phased array antenna.

[0011] The liquid crystal phased array antenna is used to receive the beam pointing signal sent by the FPGA beam control module and the transmission signal sent by the radio frequency link, and drive the liquid crystal phased array antenna to form a beam pointing in the corresponding direction, and radiate the beam towards the satellite.

[0012] The radio frequency link is used to receive satellite radio frequency signals, extract the strength information of the satellite radio frequency signals to obtain an AGC signal, and feed the AGC signal back to the FPGA wave control module; receive ground service data, perform frequency conversion and amplification on the ground service data to obtain a transmission signal, and send the transmission signal to the liquid crystal phased array antenna.

[0013] Optional features also include a BeiDou positioning module and an inertial measurement unit;

[0014] The BeiDou positioning module is used to receive BeiDou satellite navigation signals and calculate the carrier's position information, and send the carrier's position information to the ARM processor; the carrier's position information includes the carrier's latitude and longitude, altitude, speed and UTC information;

[0015] The inertial measurement unit is used to collect inertial measurement data of the carrier and send the inertial measurement data to the FPGA wave control module; the inertial measurement data of the carrier includes the three-axis angular velocity and three-axis acceleration of the carrier.

[0016] Optionally, the ARM processor is used to calculate the theoretical pointing angle of the satellite based on preset low-Earth orbit satellite two-line orbital element ephemeris data and carrier position information, and to perform coordinate transformation between the theoretical pointing angle of the satellite and the carrier attitude angle to obtain the target beam pointing angle, including:

[0017] Using the SGP4 orbit prediction model, the preset two-line orbital element ephemeris data of low-Earth orbit satellites are calculated to obtain the real-time position information of the satellites in the geocentric inertial coordinate system.

[0018] The satellite's real-time position information and the carrier's position information are transformed by coordinate transformation to obtain the azimuth and elevation angles of the satellite relative to the carrier. The azimuth and elevation angles are then used as the satellite's theoretical pointing angle.

[0019] Establish a northeast-sky coordinate system with the carrier's position information as the origin, and convert the satellite's theoretical pointing angle into a satellite direction vector under the northeast-sky coordinate system;

[0020] Based on the pitch, roll, and yaw angles of the carrier attitude angles, a rotation matrix R is constructed, R = Rx(Roll)·Ry(Pitch)·Rz(Yaw); where Rx, Ry, and Rz represent the rotation matrices about the X, Y, and Z axes, respectively; and Roll, Pitch, and Yaw represent the roll, pitch, and yaw angles, respectively.

[0021] The satellite direction vector in the northeast sky coordinate system is converted into the satellite direction vector in the array surface coordinate system through the rotation matrix, and the satellite direction vector in the array surface coordinate system is used as the target beam pointing angle.

[0022] Optionally, the FPGA beam control module is used to perform a search task to calculate the beam pointing according to the target beam pointing command, including:

[0023] According to the target beam pointing angle in the target beam pointing instruction, the search task is executed. Starting from the target beam pointing angle, the rectangular search area is expanded in circles in the order of right, down, left, and up.

[0024] The target beam pointing angle at each search location is mapped to a phase weight matrix, and the phase weight matrix is ​​used as the beam pointing at that search location.

[0025] Optionally, the FPGA beam control module is used to perform a tracking task to calculate the beam pointing error and dynamically adjust the beam pointing when the AGC signal exceeds a threshold, including:

[0026] When the AGC signal exceeds the threshold, a tracking task is executed, controlling the beam to move in a circle around the estimated center point, and collecting the AGC signal values ​​of symmetrical points on the circle respectively.

[0027] By comparing the difference in AGC signal values ​​at symmetrical points, the beam pointing error Δθaz in the azimuth direction and the beam pointing error Δθel in the elevation direction are calculated.

[0028] The beam pointing errors Δθaz in the azimuth direction and Δθel in the elevation direction are superimposed on the estimated center point to obtain the updated estimated center point azimuth angle θaz_new, θaz_new=θaz_center+k·Δθaz and the updated estimated center point elevation angle θel_new, θel_new=θel_center+k·Δθel, thus dynamically updating the beam pointing. Here, k represents the convergence factor, and θaz_center and θel_center represent the estimated center point azimuth angle and estimated center point elevation angle before the update, respectively.

[0029] Optionally, the liquid crystal phased array antenna integrates a liquid crystal cell array, row and column driving chips, and a bias voltage board;

[0030] The row and column driver chip is used to receive the beam direction sent by the FPGA beam control module, convert the beam direction into an analog voltage, and apply it to each liquid crystal cell in the liquid crystal cell array;

[0031] A bias voltage plate is used to generate a gamma bias voltage, which controls the orientation of liquid crystal molecules in each liquid crystal cell and modulates the phase of the microwave signal passing through each liquid crystal cell.

[0032] The liquid crystal cell array is used to receive the transmitted signal sent by the radio frequency link, and synthesize a beam with a specific direction according to the phase of the microwave signal of each liquid crystal cell, and radiate the beam towards the satellite.

[0033] Optionally, the RF link integrates a low-noise amplifier, a filter, a downconverter, an upconverter, a power amplifier, and a dual-mode receiver;

[0034] The low-noise amplifier is used to receive satellite radio frequency signals, amplify the satellite radio frequency signals to obtain an amplified signal, and send the amplified signal to the downconverter.

[0035] The downconverter is used to receive the amplified signal sent by the low-noise amplifier, mix the amplified signal with the local oscillator signal to obtain a mixed signal, downconvert the mixed signal to an intermediate frequency signal, and send the intermediate frequency signal to the filter.

[0036] The filter is used to receive the intermediate frequency signal sent by the downconverter, perform image frequency and out-of-band noise suppression on the intermediate frequency signal to obtain a suppressed signal, and send the suppressed signal to the dual-mode receiver.

[0037] The dual-mode receiver is used to receive the suppression signal sent by the filter, extract the intensity information of the suppression signal to obtain the AGC signal, and feed the AGC signal back to the FPGA wave control module.

[0038] The upconverter is used to receive ground service data, upconvert the ground service data to a band signal, and send the band signal to the power amplifier.

[0039] A power amplifier is used to receive the band signal sent by the upconverter, amplify the power of the band signal to the output power to obtain the transmission signal, and send the transmission signal to the liquid crystal phased array antenna.

[0040] Optionally, it also includes a temperature control module, wherein the temperature control module uses a PI film heating element attached to the liquid crystal phased array antenna;

[0041] The main controller monitors the temperature of the LCD panel of the LCD phased array antenna and adjusts the power of the PI film heating element through PWM signal to stabilize the LCD temperature within the optimal operating range.

[0042] Optionally, it may also include a communication and monitoring module, which integrates an Internet of Things module and a monitoring service module;

[0043] The IoT module is used to acquire system status frames from the main controller and the liquid crystal phased array antenna in real time, and upload the system status frames to the remote management platform at fixed intervals. At the same time, it receives remote commands issued by the remote management platform. The system status frame includes the current beam pointing angle, AGC signal, liquid crystal panel temperature of the liquid crystal phased array antenna, carrier position information, and beam pointing error. The remote commands include switching target satellites and updating the two lines of orbital element ephemeris data of low-orbit satellites.

[0044] The monitoring service module runs on an ARM processor and provides a local monitoring interface, allowing users to view beam pointing trajectory, AGC signal change curves, and system alarm information in real time within the local area network.

[0045] Optionally, it also includes a power module, which is connected to the main controller, the liquid crystal phased array antenna, the radio frequency link, the temperature control module, and the communication and monitoring module.

[0046] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0047] This invention integrates an ARM processor and an FPGA beam control module into a single chip. The ARM processor is responsible for high-level task scheduling, while the FPGA beam control module implements low-latency critical tasks in hardware. The interconnection between the ARM processor and the FPGA beam control module eliminates the physical interface latency found in traditional computer and independent FPGA beam control board architectures, achieving hardware-software collaborative beam control. The intelligent beam pointing system integrates BeiDou positioning and closed-loop feedback. The carrier position information received by the main controller serves as the absolute position reference for calculating the satellite's theoretical pointing angle. Combined with the two lines of orbital element ephemeris data from the low-Earth orbit satellite, the ARM processor calculates the satellite's theoretical pointing angle, and the FPGA beam control module executes a search algorithm to drive the antenna to scan within a preset rectangular area. Based on the feedback AGC signal, the FPGA beam control module executes a tracking algorithm, providing high-frequency attitude compensation during short-term satellite signal interruptions or severe carrier maneuvers to ensure the continuity of beam control. This forms a closed-loop control system encompassing BeiDou positioning, theoretical pointing calculation, search and acquisition, scanning and tracking, and AGC feedback correction. Attached Figure Description

[0048] Figure 1 A schematic diagram of the structure of an FPGA-based liquid crystal phased array system provided in an embodiment of the present invention;

[0049] Figure 2 This is a schematic flowchart of the control method for an FPGA-based liquid crystal phased array system provided in an embodiment of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0051] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0052] Example 1

[0053] This embodiment introduces an FPGA-based liquid crystal phased array system, including a main controller, a liquid crystal phased array antenna, and a radio frequency link. The main controller integrates an Advanced Reduced Instruction Set Machine (ARM) processor and a Field-Programmable Gate Array (FPGA) wave control module.

[0054] The ARM processor receives carrier position information and carrier attitude angles sent by the FPGA beam control module. Based on the preset low-Earth orbit satellite two-line orbital element ephemeris data and carrier position information, it calculates the satellite's theoretical pointing angle. It then performs coordinate transformation between the satellite's theoretical pointing angle and the carrier attitude angle to obtain the target beam pointing angle. Based on the target beam pointing angle, it generates a target beam pointing command and sends the target beam pointing command to the FPGA beam control module.

[0055] The FPGA beam control module receives inertial measurement data, target beam pointing commands sent by the ARM processor, and automatic gain control (AGC) signals sent by the RF link. It performs real-time integration calculations on the inertial measurement data to obtain the carrier attitude angle, and sends the carrier attitude angle to the ARM processor. Based on the target beam pointing command, it executes a search task to calculate the beam pointing. When the AGC signal exceeds a threshold, it executes a tracking task to calculate the beam pointing error and dynamically adjusts the beam pointing, sending the beam pointing to the liquid crystal phased array antenna.

[0056] The liquid crystal phased array antenna is used to receive the beam pointing signal sent by the FPGA beam control module and the transmission signal sent by the radio frequency link, and drive the liquid crystal phased array antenna to form a beam pointing in the corresponding direction, and radiate the beam towards the satellite.

[0057] The radio frequency link is used to receive satellite radio frequency signals, extract the strength information of the satellite radio frequency signals, obtain the AGC signal, and feed the AGC signal back to the FPGA wave control module; it also receives ground service data, performs frequency conversion and amplification on the ground service data to obtain the transmission signal, and sends the transmission signal to the liquid crystal phased array antenna.

[0058] This embodiment integrates an ARM processor and an FPGA beam control module into the same chip. The ARM processor is responsible for high-level task scheduling, while the FPGA beam control module implements low-latency critical tasks in hardware. The interconnection between the ARM and FPGA eliminates the physical interface latency found in traditional computer and independent FPGA beam control board architectures, achieving hardware-software collaborative beam control. The intelligent beam pointing system integrates BeiDou positioning and closed-loop feedback. The carrier position information received by the main controller serves as the absolute position reference for calculating the satellite's theoretical pointing angle. Combined with the two lines of orbital element ephemeris data from the low-Earth orbit satellite, the ARM processor calculates the satellite's theoretical pointing angle, and the FPGA beam control module executes a search algorithm to drive the antenna to scan within a preset rectangular area. Based on the feedback AGC signal, the FPGA beam control module executes a tracking algorithm, providing high-frequency attitude compensation during short-term satellite signal interruptions or severe carrier maneuvers to ensure the continuity of beam control. This forms a closed-loop control system encompassing BeiDou positioning, theoretical pointing calculation, search and acquisition, scanning and tracking, and AGC feedback correction.

[0059] Example 2

[0060] Based on Example 1, such as Figure 1 As shown in the figure, this embodiment introduces an FPGA-based liquid crystal phased array system, including a Beidou positioning module, an inertial measurement unit, a main controller, a liquid crystal phased array antenna, a radio frequency link, a temperature control module, a communication and monitoring module, and a power supply module.

[0061] The power supply module is connected to the main controller, LCD phased array antenna, RF link, temperature control module, and communication and monitoring module. The power supply module adopts industrial power supply to provide multiple stable and isolated DC voltages for the entire system. It is the energy foundation for the operation of the system. The isolated DC voltages can be +24V, +12V, +5V, and +3.3V.

[0062] The BeiDou positioning module receives BeiDou satellite navigation signals and calculates the carrier's position information. It transmits the carrier's position information to the ARM processor via a Universal Asynchronous Receiver / Transmitter (UART), which serves as the absolute position reference for calculating the satellite's theoretical azimuth / elevation angle. The carrier's position information includes its latitude and longitude, altitude, speed, and Coordinated Universal Time (UTC) information. This information is used by the ARM processor to calculate the satellite's theoretical pointing angle in conjunction with preset low-Earth orbit satellite two-line orbital element ephemeris data, and serves as the reference frame for coordinate transformation.

[0063] The inertial measurement unit (IMU) is used to collect inertial measurement data of the carrier and send the inertial measurement data to the FPGA beam control module through the Serial Peripheral Interface (SPI). The inertial measurement data of the carrier includes the three-axis angular velocity and three-axis acceleration of the carrier. The inertial measurement data is used to provide the FPGA beam control module to maintain beam pointing continuity when the BeiDou signal is lost, and to eliminate accumulated errors through data fusion after the BeiDou signal is restored. The FPGA reads these data and performs strapdown inertial navigation calculations. In the event of a short interruption of satellite signal or violent maneuvering of the carrier, it provides high-frequency, continuous attitude and position change information, and performs combined navigation with the BeiDou positioning module to ensure the continuity of beam control.

[0064] The main controller integrates an ARM processor and an FPGA beamforming module, employing a Zynq-7000 series chip to achieve hardware-software synergy. Its ARM processor handles high-level tasks: parsing remote commands from the communication and monitoring modules, running BeiDou positioning and satellite orbit prediction algorithms, and performing system monitoring. Its FPGA beamforming module implements low-latency critical tasks in hardware: real-time processing of inertial measurement data, running beamforming algorithms, generating precise timing sequences for driving the LCD, and managing data acquisition from the BeiDou positioning module and the inertial measurement unit.

[0065] ARM processors are used for:

[0066] First, it receives the carrier position information sent by the Beidou positioning module and the carrier attitude angle sent by the FPGA wave control module;

[0067] Then, based on the preset low-Earth orbit satellite two-line orbital element ephemeris data and carrier position information, the satellite's theoretical pointing angle is calculated. The satellite's theoretical pointing angle includes the satellite's theoretical azimuth angle and theoretical elevation angle. The satellite's theoretical pointing angle and carrier attitude angle are then transformed using coordinates to obtain the target beam pointing angle, including:

[0068] By simplifying the generalized perturbations 4 (SGP4) orbit prediction model, the preset two-line orbital element ephemeris data of low-Earth orbit satellites are solved to obtain the real-time position information of the satellites in the geocentric inertial coordinate system.

[0069] The satellite's real-time position information and the carrier's position information are transformed by coordinates to obtain the azimuth and elevation angles of the satellite relative to the carrier. The azimuth and elevation angles are then used as the satellite's theoretical pointing angle.

[0070] Establish a northeast-sky coordinate system with the carrier's position information as the origin, and convert the satellite's theoretical pointing angle into a satellite direction vector under the northeast-sky coordinate system;

[0071] Based on the pitch, roll, and yaw angles of the carrier attitude angles, a rotation matrix R is constructed, R = Rx(Roll)·Ry(Pitch)·Rz(Yaw); where Rx, Ry, and Rz represent the rotation matrices about the X, Y, and Z axes, respectively; and Roll, Pitch, and Yaw represent the roll, pitch, and yaw angles, respectively.

[0072] By using a rotation matrix, the satellite direction vector in the northeast sky coordinate system is converted into the satellite direction vector in the array coordinate system, and the satellite direction vector in the array coordinate system is used as the target beam pointing angle;

[0073] Finally, based on the target beam pointing angle, a target beam pointing command is generated and sent to the FPGA beam control module.

[0074] The FPGA wave control module is not a standalone chip, but a dedicated algorithm hardware circuit running within the FPGA logic, used for:

[0075] First, it receives inertial measurement data sent by the inertial measurement unit, target beam pointing instructions sent by the ARM processor, and AGC signals sent by the radio frequency link;

[0076] Then, the strapdown inertial navigation calculation module inside the FPGA performs real-time integration calculation on the inertial measurement data to obtain the carrier attitude angle, and sends the carrier attitude angle to the ARM processor.

[0077] Next, when the AGC signal does not exceed the threshold, the system state machine determines that no satellite signal has been acquired. Based on the target beam pointing command, it executes a search task to calculate the beam pointing. The typical threshold value is 2.0V, including:

[0078] Based on the target beam pointing angle in the target beam pointing command, the search task is executed. Starting from the target beam pointing angle, the rectangular search area is expanded in circles in the order of right, down, left, and up.

[0079] Each time a new position is moved, the target beam pointing angle of each search position is mapped to a phase weight matrix through a lookup table, and the phase weight matrix is ​​used as the beam pointing of that search position.

[0080] When the AGC signal exceeds the threshold, a tracking task is executed to calculate the beam pointing error and dynamically adjust the beam pointing, including:

[0081] When the AGC signal exceeds the threshold, a tracking task is executed, controlling the beam to move in a circle around the estimated center point, and collecting the AGC signal values ​​of symmetrical points on the circle respectively.

[0082] By comparing the difference in AGC signal values ​​at symmetrical points, the beam pointing error Δθaz in the azimuth direction and the beam pointing error Δθel in the elevation direction are calculated.

[0083] The beam pointing errors Δθaz in the azimuth direction and Δθel in the elevation direction are superimposed on the estimated center point to obtain the updated estimated center point azimuth angle θaz_new, θaz_new=θaz_center+k·Δθaz, and the updated estimated center point elevation angle θel_new, θel_new=θel_center+k·Δθel, thus dynamically updating the beam pointing; where k represents the convergence factor, and θaz_center and θel_center represent the estimated center point azimuth angle and estimated center point elevation angle before the update, respectively;

[0084] The beam direction is sent to the liquid crystal phased array antenna.

[0085] The search task here is a frame search task. The target beam pointing instructions include the search center point, initial search step size, maximum number of search cycles, and AGC threshold. These parameters are transmitted to the FPGA via an on-chip high-speed bus with a latency of less than 1μs; the search center point is the theoretical pointing angle of the satellite.

[0086] The tracking task here is a conical scanning tracking task. At four symmetrical points on the circumference, for example, 0°, 90°, 180°, and 270°, the AGC signal values ​​VAGC(1), VAGC(2), VAGC(3), and VAGC(4) are collected respectively. By comparing the difference between VAGC(1) and VAGC(3), and the difference between VAGC(2) and VAGC(4), the beam pointing error Δθaz in the azimuth direction and the beam pointing error Δθel in the pitch direction are calculated. The beam pointing errors Δθaz in the azimuth direction and Δθel in the pitch direction are superimposed on the estimated center point to obtain the updated estimated center point azimuth angle θaz_new, θaz_new=θaz_center+k·Δθaz and the updated estimated center point pitch angle θel_new, θel_new=θel_center+k·Δθel, where the scaling factor k is a convergence factor of 0.5 to 0.8. The beam pointing is dynamically updated to form a closed loop of scanning, sampling, comparison and correction. During this period, the inertial measurement unit continuously provides the carrier attitude change amount, and the FPGA compensates for attitude disturbances in real time to ensure tracking continuity. The tracking loop update cycle is determined by the system clock, with a typical value of 10ms.

[0087] The liquid crystal phased array antenna does not actively transmit signals. Instead, it acts as a beamforming spatial lens, receiving beam pointing signals from the FPGA beam control module and transmission signals from the RF link. This drives the liquid crystal phased array antenna to form a beam pointing in the corresponding direction, radiating the beam towards the satellite. Specifically, the liquid crystal phased array antenna integrates a liquid crystal unit array, row and column driver chips, and a bias voltage board.

[0088] The row and column driver chip is used to receive the beam direction sent by the FPGA beam control module, convert the beam direction into an analog voltage, and apply it to each liquid crystal cell in the liquid crystal cell array.

[0089] The bias voltage plate is controlled via an interface to generate multiple programmable gamma bias voltages. The gamma bias voltages control the orientation of liquid crystal molecules in each liquid crystal cell. The change in the orientation of the liquid crystal molecules causes a change in their dielectric constant, thereby modulating the phase of the microwave signal passing through each liquid crystal cell.

[0090] The liquid crystal cell array is used to receive the transmitted signals sent by the radio frequency link. Based on the phase of the microwave signal of each liquid crystal cell, the phase of the microwave signals of thousands of liquid crystal cells changes in a coordinated manner to synthesize a beam with a specific direction, which is then radiated towards the satellite to achieve electronically controlled scanning. The transmitted signals provided by the radio frequency link are radiated or received after beamforming at this point.

[0091] The radio frequency (RF) link plays a crucial feedback role in search and tracking tasks. It receives satellite RF signals, extracts their strength information to obtain the AGC (Automatic Gain Control) signal, and feeds this signal back to the FPGA wave control module. It also receives ground service data, performs frequency conversion and amplification to obtain the transmit signal, which is then sent to the liquid crystal phased array antenna. Specifically, the satellite RF signal is a continuous wave or narrowband modulated signal with extremely low power, specifically designed for antenna pointing and tracking. A typical satellite RF signal power is -120dBm. The ground service data is a wideband digital modulated signal used for satellite communication service transmission. The RF link integrates a low-noise amplifier, filter, down-converter, up-converter, power amplifier, and dual-mode receiver.

[0092] On the receiving path:

[0093] A low-noise amplifier is used to receive Ku-band or Ka-band satellite radio frequency signals, amplify the satellite radio frequency signals, achieve a noise figure of less than 1.5dB, and a gain of 30dB to 40dB to obtain an amplified signal, which is then sent to a downconverter. Ku-band satellite radio frequency signals refer to satellite radio frequency signals from 12GHz to 18GHz, and Ka-band satellite radio frequency signals refer to satellite radio frequency signals from 26.5GHz to 40GHz.

[0094] The downconverter receives the amplified signal from the low-noise amplifier, mixes the amplified signal with the local oscillator signal to obtain a mixed signal, downconverts the mixed signal to an intermediate frequency (IF) signal, and sends the IF signal to a filter; the IF signal frequency is 950MHz to 2150MHz.

[0095] The filter is used to receive the intermediate frequency signal sent by the downconverter, perform image frequency and out-of-band noise suppression on the intermediate frequency signal to obtain a suppressed signal, and send the suppressed signal to the dual-mode receiver.

[0096] The dual-mode receiver integrates a demodulator to receive the suppressed signal sent by the filter. The beacon demodulator extracts the strength information of the suppressed signal to obtain the AGC signal. This voltage signal has a linear relationship with the input signal power; the higher the voltage, the stronger the received signal. The AGC signal is fed back to the FPGA wave control module. The AGC signal is a voltage signal from 0V to 10V.

[0097] The AGC voltage is sampled by an internal or external ADC chip in the FPGA at a frequency of 100Hz to 1kHz, converted into a 12-bit digital value with a resolution of approximately 2.44mV, corresponding to a power resolution of approximately 0.1dB. This value is used by the frame search state machine and the conical scan tracking algorithm to ensure that the sampling is synchronized with the wave control timing. The dual-mode receiver communicates with the ARM controller via an interface. The ARM controller sends commands to set the operating mode and frequency of the dual-mode receiver. The dual-mode receiver operating modes include beacon mode and data mode.

[0098] On the transmit path, a liquid crystal phased array antenna is shared with the receive path. The liquid crystal phased array antenna shared by the transmit and receive paths is a reciprocal device.

[0099] The upconverter is used to receive terrestrial service data, upconvert the terrestrial service data to Ku-band or Ka-band signals, and send the band signals to the power amplifier; Ku-band signals refer to band signals from 14 GHz to 14.5 GHz, and Ka-band signals refer to band signals from 27 GHz to 31 GHz.

[0100] The power amplifier is used to receive the band signal sent by the upconverter, amplify the power of the band signal to the output power to obtain the transmission signal, and send the transmission signal to the liquid crystal phased array antenna. The output power is 1W to 10W.

[0101] A transceiver duplexer is connected between the liquid crystal phased array antenna and the low-noise amplifier, and between the liquid crystal phased array antenna and the power amplifier, to isolate the received signal and the transmitted signal and prevent the transmitted signal from leaking into the receiving path. The isolation of the transceiver duplexer is greater than 80dB.

[0102] At this point, the FPGA beam control module has mapped the target beam pointing angle to the phase weight matrix of each liquid crystal unit. This matrix is ​​then applied to the liquid crystal units via the row and column driver chips. The phases of each antenna unit change in tandem, spatially synthesizing a high-gain directional beam that radiates the transmitted signal toward the satellite, thus establishing the uplink. Due to the reciprocity of the liquid crystal phased array, the same set of phase weights is used for both transmission and reception, eliminating the need for separate calculation of the transmitted beam pointing.

[0103] The temperature control module uses a polyimide (PI) film heating element attached to the back of the liquid crystal phased array antenna;

[0104] The FPGA beam control module or ARM processor in the main controller monitors the temperature of the liquid crystal panel of the liquid crystal phased array antenna through a temperature sensor, and controls the on and off of the heating element through pulse width modulation (PWM) or relay to form a closed-loop temperature control. That is, the power of the PI film heating element is adjusted by the PWM signal to stabilize the liquid crystal temperature in the optimal operating range, ensure the dielectric constant is stable, maintain the phase control accuracy, and thus ensure the beam pointing accuracy.

[0105] The communication and monitoring module integrates the Internet of Things (IoT) module and the monitoring service module; the IoT module is a 4G IoT module.

[0106] The IoT module is used to acquire system status frames from the main controller and the LCD phased array antenna in real time, and upload the system status frames to the remote management platform at fixed intervals. At the same time, it receives remote commands issued by the remote management platform. The system status frames include the current beam pointing angle, AGC signal, LCD panel temperature of the LCD phased array antenna, carrier position information and beam pointing error. The remote commands include switching target satellites and updating the two lines of orbital element ephemeris data of low-Earth orbit satellites.

[0107] The monitoring service module, running on an ARM processor, provides a local monitoring interface, allowing users to view beam pointing trajectory, AGC signal change curves, and system alarm information in real time within the local area network.

[0108] After system startup, the BeiDou positioning module provides the carrier's location information. Combined with preset low-Earth orbit satellite orbit element ephemeris data, it calculates the satellite's theoretical pointing direction. The ARM architecture plans the search task, and the FPGA beam control logic executes the frame search, driving antenna scanning. Simultaneously, the dual-mode receiver feeds back the AGC signal. Once the AGC signal exceeds a threshold, the system switches to a conical scanning tracking task: the FPGA controls the beam to move in a circle around the estimated center, collecting AGC values ​​at symmetrical points on the circle and comparing them in real time to calculate the beam pointing error. The beam center is then dynamically adjusted, forming a closed loop of sensor perception, controller calculation, beam control execution, and signal feedback. The inertial measurement unit provides high-frequency attitude compensation throughout the process, the temperature control module maintains the LCD's operating environment, and the communication and monitoring module enables status transmission and remote intervention. All modules are powered by a unified power supply module and interconnected to form a complete and collaborative automatic tracking system.

[0109] Example 3

[0110] Based on Example 2, such as Figure 2 As shown in the figure, this embodiment introduces a control method for a liquid crystal phased array system based on FPGA, including the following steps:

[0111] The system is powered on or reset.

[0112] Step 1: Pre-configuration, specifically:

[0113] Because this system is quite complex and uses many peripherals, there is a lot of preparatory work to be done before initialization. This mainly includes FPGA configuration, memory configuration, communication interface configuration, dual-mode receiver configuration, creating conical scanning sine and cosine tables, processing serial port data, and processing network port data.

[0114] Configuring the main control chip FPGA. FPGAs have many internal resources, but these resources must be configured before use.

[0115] Configuring the dual-mode receiver. First, perform the initial configuration of the dual-mode receiver, then set the symbol rate and local oscillator frequency; finally, determine whether the dual-mode receiver can work properly.

[0116] Create a sine and cosine table for conical scanning. This system uses a conical scanning tracking method, requiring the antenna to perform circular motion. Since the motor can only move linearly, it can only be controlled to make small-amplitude linear movements to simulate circular motion. The motor's trajectory is not actually a true circle, but rather an inscribed regular polygon. The circle is decomposed into azimuth and elevation values ​​according to sine and cosine values, and then tabulated. This way, the motor moves according to the values ​​in the table, simulating circular motion. Decomposing the circle according to sine and cosine values ​​allows for horizontal and vertical decomposition, with the decomposition values ​​being sine and cosine, respectively.

[0117] Process serial port data. Before initializing the antenna, the commands sent by the host computer via the serial port must be processed. Only after this is completed can the following steps be performed.

[0118] Step 2: Antenna initialization, specifically:

[0119] Set the antenna's physical state to zero or reset, for example, by pointing the beam to the initial position, turning off the heater / fan, or turning on the heater / fan according to the temperature, to prepare for the search to begin.

[0120] Step 3: Frame search, specifically:

[0121] This is the acquisition phase. When the system does not know the exact location of the satellite, the FPGA drives the liquid crystal phased array antenna to scan a preset rectangular area in the sky, which is the frame.

[0122] By combining the carrier's location information and inertial measurement data, the starting point and range of the search are determined.

[0123] Step 4: Tracking scan, specifically:

[0124] This is the tracking phase. Once a signal is detected in step three, the system switches to conical scanning mode. The antenna beam makes a small circular motion around the estimated center point, and the deviation is judged by the AGC signal strength fed back in real time by the dual-mode receiver. The detection of a signal in step three means that the AGC signal exceeds the threshold.

[0125] Using the AGC signal as feedback, the algorithm calculates the error and dynamically adjusts the beam direction to form a closed-loop control. The AGC signal is a voltage signal from 0 V to 10 V.

[0126] The process ends. In a real system, this is usually a loop point, where the process returns to data processing or continues to the next round of tracking.

[0127] Data processing is crucial throughout the entire process. Both receiver data and external commands need to be processed in real time to support search and tracking decisions.

[0128] This embodiment utilizes the programmable nature of electronic control to generate low-sidelobe, high-gain beams, effectively suppressing multipath interference and improving the signal-to-noise ratio of the satellite link. Simultaneously, rapid beam switching ensures the stability of the communication link during the brief window of low-Earth orbit satellite overhead. By employing a main controller chip instead of a multi-chip solution and a serial bus instead of a parallel bus, and leveraging the low power consumption of the liquid crystal material, the overall system size and weight are reduced, making it easier to integrate into vehicle-mounted, ship-mounted, or portable terminals. The low power consumption extends the device's battery life in environments without mains power, aligning with the trend of green communication. The dielectric constant of the liquid crystal material is temperature-sensitive; the temperature control module ensures stable performance of the liquid crystal over a wide temperature range, enabling the system to operate stably under extreme climatic conditions. Phase control accuracy is not degraded by ambient temperature fluctuations, meeting the application requirements of harsh scenarios such as military and emergency communications. This wide temperature range refers to -40°C to +85°C, and extreme climatic conditions refer to extremely cold and hot climates.

[0129] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0130] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0131] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0132] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0133] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A liquid crystal phased array system based on FPGA, characterized in that, It includes a main controller, a liquid crystal phased array antenna, and a radio frequency link. The main controller integrates an ARM processor and an FPGA wave control module. The ARM processor is used to receive carrier position information and carrier attitude angle sent by the FPGA beam control module. Based on the preset low-orbit satellite two-line orbital element ephemeris data and carrier position information, it calculates the satellite theoretical pointing angle, performs coordinate transformation between the satellite theoretical pointing angle and the carrier attitude angle to obtain the target beam pointing angle, generates a target beam pointing command based on the target beam pointing angle, and sends the target beam pointing command to the FPGA beam control module. The FPGA beam control module is used to receive inertial measurement data, target beam pointing instructions sent by the ARM processor, and AGC signals sent by the RF link. It performs real-time integration calculation on the inertial measurement data to obtain the carrier attitude angle and sends the carrier attitude angle to the ARM processor. According to the target beam pointing instructions, it executes a search task to calculate the beam pointing. When the AGC signal exceeds a threshold, it executes a tracking task to calculate the beam pointing error and dynamically adjusts the beam pointing. The beam pointing is then sent to the liquid crystal phased array antenna. The liquid crystal phased array antenna is used to receive the beam pointing signal sent by the FPGA beam control module and the transmission signal sent by the radio frequency link, and drive the liquid crystal phased array antenna to form a beam pointing in the corresponding direction, and radiate the beam towards the satellite. The radio frequency link is used to receive satellite radio frequency signals, extract the strength information of the satellite radio frequency signals, obtain AGC signals, and feed back the AGC signals to the FPGA wave control module. The system receives ground service data, performs frequency conversion and amplification on the ground service data to obtain a transmission signal, and sends the transmission signal to a liquid crystal phased array antenna.

2. The FPGA-based liquid crystal phased array system according to claim 1, characterized in that, It also includes a BeiDou positioning module and an inertial measurement unit; The BeiDou positioning module is used to receive BeiDou satellite navigation signals and calculate the carrier's position information, and send the carrier's position information to the ARM processor; the carrier's position information includes the carrier's latitude and longitude, altitude, speed and UTC information; The inertial measurement unit is used to collect inertial measurement data of the carrier and send the inertial measurement data to the FPGA wave control module; the inertial measurement data of the carrier includes the three-axis angular velocity and three-axis acceleration of the carrier.

3. The FPGA-based liquid crystal phased array system according to claim 1, characterized in that, The ARM processor is used to calculate the theoretical pointing angle of the satellite based on preset low-Earth orbit satellite two-line orbital element ephemeris data and carrier position information, and to perform coordinate transformation between the theoretical pointing angle of the satellite and the carrier attitude angle to obtain the target beam pointing angle, including: Using the SGP4 orbit prediction model, the preset two-line orbital element ephemeris data of low-Earth orbit satellites are calculated to obtain the real-time position information of the satellites in the geocentric inertial coordinate system. The satellite's real-time position information and the carrier's position information are transformed by coordinate transformation to obtain the azimuth and elevation angles of the satellite relative to the carrier. The azimuth and elevation angles are then used as the satellite's theoretical pointing angle. Establish a northeast-sky coordinate system with the carrier's position information as the origin, and convert the satellite's theoretical pointing angle into a satellite direction vector under the northeast-sky coordinate system; Based on the pitch, roll, and yaw angles of the carrier attitude angles, a rotation matrix R is constructed, R = Rx(Roll)·Ry(Pitch)·Rz(Yaw); where Rx, Ry, and Rz represent the rotation matrices about the X, Y, and Z axes, respectively; and Roll, Pitch, and Yaw represent the roll, pitch, and yaw angles, respectively. The satellite direction vector in the northeast sky coordinate system is converted into the satellite direction vector in the array surface coordinate system through the rotation matrix, and the satellite direction vector in the array surface coordinate system is used as the target beam pointing angle.

4. The FPGA-based liquid crystal phased array system according to claim 1, characterized in that, The FPGA beam control module is used to perform a search task to calculate the beam pointing according to the target beam pointing command, including: According to the target beam pointing angle in the target beam pointing instruction, the search task is executed. Starting from the target beam pointing angle, the rectangular search area is expanded in circles in the order of right, down, left, and up. The target beam pointing angle at each search location is mapped to a phase weight matrix, and the phase weight matrix is ​​used as the beam pointing at that search location.

5. The FPGA-based liquid crystal phased array system according to claim 1, characterized in that, The FPGA beam control module is used to perform a tracking task to calculate the beam pointing error and dynamically adjust the beam pointing when the AGC signal exceeds a threshold, including: When the AGC signal exceeds the threshold, a tracking task is executed, controlling the beam to move in a circle around the estimated center point, and collecting the AGC signal values ​​of symmetrical points on the circle respectively. By comparing the difference in AGC signal values ​​at symmetrical points, the beam pointing error Δθaz in the azimuth direction and the beam pointing error Δθel in the elevation direction are calculated. The beam pointing errors Δθaz in the azimuth direction and Δθel in the elevation direction are superimposed on the estimated center point to obtain the updated estimated center point azimuth angle θaz_new, θaz_new=θaz_center+k·Δθaz and the updated estimated center point elevation angle θel_new, θel_new=θel_center+k·Δθel, thus dynamically updating the beam pointing. Here, k represents the convergence factor, and θaz_center and θel_center represent the estimated center point azimuth angle and estimated center point elevation angle before the update, respectively.

6. The FPGA-based liquid crystal phased array system according to claim 1, characterized in that, The liquid crystal phased array antenna integrates a liquid crystal unit array, row and column driving chips, and a bias voltage board. The row and column driver chip is used to receive the beam direction sent by the FPGA beam control module, convert the beam direction into an analog voltage, and apply it to each liquid crystal cell in the liquid crystal cell array; A bias voltage plate is used to generate a gamma bias voltage, which controls the orientation of liquid crystal molecules in each liquid crystal cell and modulates the phase of the microwave signal passing through each liquid crystal cell. The liquid crystal cell array is used to receive the transmitted signal sent by the radio frequency link, and synthesize a beam with a specific direction according to the phase of the microwave signal of each liquid crystal cell, and radiate the beam towards the satellite.

7. The FPGA-based liquid crystal phased array system according to claim 6, characterized in that, The radio frequency link integrates a low-noise amplifier, filter, downconverter, upconverter, power amplifier, and dual-mode receiver; The low-noise amplifier is used to receive satellite radio frequency signals, amplify the satellite radio frequency signals to obtain an amplified signal, and send the amplified signal to the downconverter. The downconverter is used to receive the amplified signal sent by the low-noise amplifier, mix the amplified signal with the local oscillator signal to obtain a mixed signal, downconvert the mixed signal to an intermediate frequency signal, and send the intermediate frequency signal to the filter. The filter is used to receive the intermediate frequency signal sent by the downconverter, perform image frequency and out-of-band noise suppression on the intermediate frequency signal to obtain a suppressed signal, and send the suppressed signal to the dual-mode receiver. The dual-mode receiver is used to receive the suppression signal sent by the filter, extract the intensity information of the suppression signal to obtain the AGC signal, and feed the AGC signal back to the FPGA wave control module. The upconverter is used to receive ground service data, upconvert the ground service data to a band signal, and send the band signal to the power amplifier. A power amplifier is used to receive the band signal sent by the upconverter, amplify the power of the band signal to the output power to obtain the transmission signal, and send the transmission signal to the liquid crystal phased array antenna.

8. The FPGA-based liquid crystal phased array system according to claim 1, characterized in that, It also includes a temperature control module, which uses a PI film heating element attached to the liquid crystal phased array antenna; The main controller monitors the temperature of the LCD panel of the LCD phased array antenna and adjusts the power of the PI film heating element through PWM signal to stabilize the LCD temperature within the optimal operating range.

9. The FPGA-based liquid crystal phased array system according to claim 8, characterized in that, It also includes a communication and monitoring module, which integrates an Internet of Things (IoT) module and a monitoring service module; The IoT module is used to acquire system status frames from the main controller and the liquid crystal phased array antenna in real time, and upload the system status frames to the remote management platform at fixed intervals. At the same time, it receives remote commands issued by the remote management platform. The system status frame includes the current beam pointing angle, AGC signal, liquid crystal panel temperature of the liquid crystal phased array antenna, carrier position information, and beam pointing error. The remote commands include switching target satellites and updating the two lines of orbital element ephemeris data of low-orbit satellites. The monitoring service module runs on an ARM processor and provides a local monitoring interface, allowing users to view beam pointing trajectory, AGC signal change curves, and system alarm information in real time within the local area network.

10. The FPGA-based liquid crystal phased array system according to claim 9, characterized in that, It also includes a power module, which is connected to the main controller, the liquid crystal phased array antenna, the radio frequency link, the temperature control module, and the communication and monitoring module.

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