Liquid crystal phased array based high-low orbit satellite signal switching and calibration system and method

Abstract

The application provides a high-low orbit satellite signal switching and calibration system and method based on a liquid crystal phased array, relates to the technical field of satellite communication, and comprises a liquid crystal phased array antenna module, a beam control module, a dynamic calibration module and a link adaptation module.The liquid crystal phased array antenna module is used for realizing the reception and emission of high-low orbit satellite signals, contains a plurality of independently controllable liquid crystal phase-shifting units, and realizes inertia-free electronic scanning and multi-beam generation through voltage regulation.The beam control module is connected with the liquid crystal phased array antenna module.The application adopts a liquid crystal phased array antenna to replace a traditional mechanical scanning antenna and a gallium arsenide phased array antenna, realizes millisecond-level beam switching through inertia-free electronic scanning, supports the multi-beam generation capacity of one surface to multiple satellites, significantly simplifies the terminal architecture, reduces the volume, weight and power consumption of the equipment, solves the pain points of large switching delay and limited deployment of traditional equipment, and adapts to the application requirements of multiple scenes such as satellite and vehicle.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and in particular to a high- and low-orbit satellite signal switching and calibration system and method based on a liquid crystal phased array. Background Technology

[0002] In existing high-Earth orbit (HEO) and low-Earth orbit (LEO) satellite collaborative communication systems, HEO satellites rely on geostationary orbit to achieve wide-area stable coverage, with signal transmission primarily using satellite-to-ground links. Long-distance communication is achieved through a ground station-satellite-target terminal relay mode. LEO satellites, on the other hand, construct a seamless global coverage network through a giant constellation and inter-satellite links, achieving low-latency communication over short transmission distances. The collaboration between the two systems complements each other's strengths and weaknesses to meet diverse service needs. Currently, the core equipment for HEO-LEO collaboration mainly relies on mechanically scanned antennas and traditional gallium arsenide (GaAs) phased array antennas. Mechanically scanned antennas adjust beam pointing through physical rotation, while traditional phased array antennas achieve beamforming and switching through independent TR (transformer array) components. Both types of equipment are widely used in existing HEO-LEO collaborative scenarios.

[0003] However, in existing technologies, mechanically scanned antennas are limited by mechanical inertia, resulting in slow scanning speeds, switching delays on the order of seconds, low reliability, and large size and weight. They cannot meet the rapid link switching requirements caused by the high-speed movement of low-Earth orbit satellites and are difficult to deploy on mobile platforms. Traditional gallium arsenide phased array antennas have extremely high costs and power consumption, complex calibration processes, and require frequent field interventions, making heat dissipation difficult and restricting large-scale deployment. At the same time, existing systems lack an integrated switching protocol for the heterogeneous characteristics of high and low orbits, and face problems such as time delay differences and Doppler frequency offset during inter-orbit switching. Furthermore, equipment parameter drift caused by the space environment and atmospheric turbulence interference further exacerbate link instability, seriously affecting communication continuity and transmission quality. Therefore, this invention proposes a high and low orbit satellite signal switching and calibration system and method based on liquid crystal phased arrays to solve the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a high- and low-orbit satellite signal switching and calibration system and method based on a liquid crystal phased array. It replaces traditional mechanical scanning antennas and gallium arsenide phased array antennas with a liquid crystal phased array antenna, achieving millisecond-level beam switching through inertial-free electronic scanning. Furthermore, it supports multi-beam generation capability for multiple satellites on a single surface, significantly simplifying the terminal architecture and reducing equipment size, weight, and power consumption. This solves the pain points of large switching delays and limited deployment associated with traditional equipment, making it suitable for various application scenarios such as spaceborne and vehicle-mounted systems.

[0005] To achieve the objectives of this invention, the following technical solution is employed: a high- and low-Earth orbit satellite signal switching and calibration system based on a liquid crystal phased array (LCD) includes an LCD phased array antenna module, a beam control module, a dynamic calibration module, and a link adaptation module. The LCD phased array antenna module is used for receiving and transmitting high- and low-Earth orbit satellite signals and includes several independently controllable liquid crystal phase-shifting units. Voltage regulation enables inertial-free electronic beam scanning and multi-beam generation. The beam control module is connected to the LCD phased array antenna module and pre-stores high- and low-Earth orbit satellite ephemeris data and typical wavefront phase tables. It is used to calculate the relative azimuth angle of the satellite in real time and output beam pointing control commands. The dynamic calibration module is integrated into the LCD phased array antenna module and includes a calibration signal source, a power divider network, a coupler array, and an amplitude and phase detector unit. It is used to achieve antenna channel amplitude and phase reference calibration, temperature-phase drift compensation, and joint calibration of the air interface pilot. The link adaptation module is linked with the beam control module and the dynamic calibration module to achieve polarization mode matching, inter-satellite delay compensation, Doppler frequency offset correction, and adaptive adjustment of frequency band and power.

[0006] The beam control module triggers the liquid crystal phased array antenna module to complete high- and low-orbit beam switching through a parallel phase driving mechanism. The dynamic calibration module compensates for link errors in real time, and the link adaptation module optimizes transmission parameters synchronously, thereby achieving seamless switching and stable transmission of high- and low-orbit satellite signals.

[0007] Further improvements are made in that: the liquid crystal phased array antenna module adopts a 4×4 array architecture, the liquid crystal phase shifting unit is made based on nematic liquid crystal material, the phase shifting accuracy of a single unit is ≥1.4°, and it supports continuous phase adjustment from 0 to 360°. The antenna panel can generate at least one high-orbit pointing beam and three low-orbit pointing beams simultaneously through partition control.

[0008] Further improvements are made in that: the dynamic calibration module adopts an integrated architecture of calibration signal source-power divider network-coupler-detector, and shares a substrate with the liquid crystal phased array antenna feed network. The overall thickness is <0.8mm and the weight is <50mW. The calibration signal source is a Ka / Ku dual-mode phase-locked loop (PLL) signal source with an output frequency range of 19.5-26.0GHz.

[0009] Further improvements are made in that the beam control module is built on an FPGA chip and integrates a track parameter calculation unit, a beam position fast identification unit and a parallel phase drive unit. The parallel phase drive unit adopts a 16-channel high-voltage DAC array with an output voltage range of 0-20V and a conversion rate of ≥1MSps, realizing synchronous voltage loading of 16 phase shifters.

[0010] A method for switching and calibrating high and low orbit satellite signals based on liquid crystal phased arrays includes the following steps:

[0011] S1: Pre-configuration stage: Obtain orbital parameters and ephemeris data of high and low orbit satellites, calculate the phase shifter voltage-phase mapping relationship corresponding to typical wave positions, generate inter-orbit wave position phase table and initial values ​​of calibration coefficients, and store them in the beam control module.

[0012] S2: Dynamic beam tracking and switching. The beam control module calculates the relative azimuth angle of the satellite in real time, matches the optimal beam position, and controls the liquid crystal phased array antenna module through a parallel phase drive mechanism to achieve millisecond-level beam pointing adjustment and complete the high- and low-orbit satellite link switching.

[0013] S3: Multi-dimensional dynamic calibration, based on a three-level calibration triggering mechanism, uses channel amplitude and phase reference calibration, temperature-phase drift compensation and air interface pilot joint calibration algorithm to correct antenna channel error and link phase deviation in real time;

[0014] S4: Link parameter adaptive adaptation. The link adaptation module monitors link quality indicators and dynamically adjusts polarization mode, transmission frequency band, radiated power and Doppler frequency offset compensation parameters to ensure link stability after handover.

[0015] Steps S2-S4 are executed in parallel to achieve coordinated switching and calibration of high and low orbit satellite signals.

[0016] Further improvements are made in S2, where beam switching adopts a pre-trigger-parallel control mechanism. When the current link signal-to-noise ratio is detected to be lower than the threshold or the target satellite enters the communication range, the target beam phase configuration is pre-read 5ms in advance, and the beam switching time is <10ms.

[0017] Further improvements are made in the following: In S3, the three-level calibration triggering mechanism includes timed calibration, threshold-triggered calibration and operating condition switching calibration. The timed calibration cycle is 24 hours. Threshold calibration is triggered when the temperature change exceeds 5°C or the channel amplitude fluctuation exceeds 0.5dB / phase fluctuation exceeds 2°. Operating condition switching calibration is triggered before high-low rail switching or frequency band switching.

[0018] A further improvement is made in S3, where the temperature-phase drift compensation is based on a three-dimensional model of liquid crystal dielectric constant-temperature-phase, and the phase shifter bias voltage is corrected using the following formula:

[0019] ,

[0020] Where V0 is the room temperature reference voltage, k is the temperature compensation coefficient, T is the real-time temperature, T0 is the room temperature reference value, and the phase error after calibration is <1°.

[0021] Further improvements are made in S4, where the Doppler frequency offset compensation employs a PLL-FFT-VV dual-mode algorithm. PLL closed-loop compensation is enabled for low-dynamic scenarios, while FFT-VV open-loop compensation is switched for high-dynamic scenarios. The root mean square error of the frequency offset estimation is... .

[0022] Further improvements are made in S4, where the polarization mode adaptation achieves real-time switching between circular and linear polarization through phase coordination control of the liquid crystal phase shifter, with the axial ratio stabilized within 3dB and the polarization loss reduced to below 0.5dB.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention uses a liquid crystal phased array antenna to replace the traditional mechanical scanning antenna and gallium arsenide phased array antenna. It achieves millisecond-level beam switching through inertial-free electronic scanning and supports multi-beam generation capability for one-sided multi-satellite communication. It significantly simplifies the terminal architecture, reduces the size, weight and power consumption of the device, and solves the pain points of large switching delay and limited deployment of traditional devices. It is suitable for application needs in multiple scenarios such as spaceborne and vehicle-mounted.

[0025] 2. This invention features an integrated dynamic calibration module and a multi-dimensional calibration algorithm. Through power-on self-calibration, online background calibration, and a three-level triggered calibration mechanism, it achieves comprehensive compensation for channel amplitude and phase deviation, temperature drift, and inter-orbit link phase difference. After calibration, the phase error is <1°. This eliminates the reliance on complex external calibration equipment, reduces maintenance costs, and improves the long-term stability of the system, making it compatible with satellite platforms. A wide temperature range working environment.

[0026] 3. This invention constructs a collaborative mechanism of beam switching, dynamic calibration, and link adaptation. Through strategies such as beam position pre-configuration, Doppler dual-mode compensation, and adaptive adjustment of polarization / frequency band / power, it effectively addresses issues such as latency differences and frequency offset interference caused by the heterogeneous characteristics of high and low orbits. The link interruption time is compressed to less than 10ms, and the polarization loss is ≤0.5dB. This significantly improves the seamlessness and anti-interference capability of high and low orbit collaborative communication, ensuring the transmission quality of services such as real-time voice and video conferencing. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the calibration process of the present invention;

[0028] Figure 2 This is a schematic diagram of the beam switching process of the present invention;

[0029] Figure 3 This is a schematic diagram illustrating the key influencing factors of the present invention;

[0030] Figure 4 This is a schematic diagram of the modeling technique for the Ka-band characteristics of liquid crystal materials according to the present invention;

[0031] Figure 5 This is a schematic diagram of the liquid crystal phase-shifting unit model of the present invention;

[0032] Figure 6 This is a schematic diagram of the direction of the broadband radiation unit of the present invention;

[0033] Figure 7 This is a schematic diagram of the large-scale array driving circuit of the present invention;

[0034] Figure 8 This is a schematic diagram illustrating the high-precision phase shifter precise control technology approach of the present invention;

[0035] Figure 9 This is a schematic diagram of the switching-adaptation linkage triggering mechanism of the present invention. Detailed Implementation

[0036] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0037] Example 1

[0038] according to Figure 1 , 2 As shown in Figures 3, 4, 5, 6, 7, 8, and 9, this embodiment proposes a high- and low-orbit satellite signal switching and calibration system and method based on a liquid crystal phased array:

[0039] Liquid crystal phased array technology:

[0040] By controlling the voltage applied to the liquid crystal cells, the alignment of the liquid crystal molecules is altered, thereby changing the phase of the radio frequency signal within milliseconds, achieving inertial-free electronic scanning for beam pointing. This eliminates the physical delay of mechanical scanning. Utilizing the inherent uniformity and repeatable driving characteristics of liquid crystal materials, combined with built-in reference sensors and intelligent calibration algorithms, self-calibration upon startup or online background calibration can be achieved. This eliminates reliance on expensive and complex field calibration equipment and frequent manual intervention, significantly reducing maintenance costs and time, and improving system availability and long-term stability. High-speed, continuous beamforming capabilities can dynamically predict and compensate for Doppler frequency shifts and angle changes caused by high-speed satellite motion in real time, significantly improving the link signal-to-noise ratio and stability in drastically dynamic environments, reducing bit errors and interruptions, and enabling high-quality continuous communication. A single liquid crystal phased array panel can generate multiple independent beams simultaneously through partitioned control, pointing to high-orbit and low-orbit satellites respectively. This achieves "one panel for multiple satellites," simplifying terminal architecture and reducing weight, size, and power consumption.

[0041] In the early stages of low-Earth orbit (LEO) satellite constellation deployment, the insufficient number of satellites prevented continuous coverage. Therefore, coordinated signal transmission between LEO and EEO satellites was crucial. Current LEO-EEO signal coordination mechanisms face challenges such as long inter-satellite transmission paths, significant signal attenuation, and transmission interruptions caused by relative motion. This paper proposes a solution that combines the wide-area coverage of EEO satellites with the low latency and high bandwidth of LEO satellites to achieve uninterrupted service transmission. On the terminal application side, liquid crystal phased array satellite terminals access the LEO satellite constellation to handle low-latency and high-bandwidth services. When an LEO satellite passes overhead, multi-beam scanning technology of the phased array locks onto an EEO satellite, smoothly switching to EEO satellite communication.

[0042] Dynamic beam tracking and switching mechanism:

[0043] Orbit parameter preloading: The antenna control module pre-stores the orbital elements of the low-Earth orbit satellite and the fixed coordinates of the high-Earth orbit satellite, and predicts the relative azimuth angle change between the low-Earth orbit satellite and the high-Earth orbit satellite through ephemeris calculation; Real-time phase compensation: The FPGA-based phase control unit calculates the scanning phase of each phase shifter according to the real-time azimuth angle, and outputs the corresponding bias voltage value after superimposing the initial phase of circular polarization, realizing millisecond-level dynamic tracking of the beam (switching time <10ms), ensuring that the link is not interrupted when the low-Earth orbit satellite moves at high speed; Multi-beam redundant coverage: The antenna is divided into four 2×2 subarrays, each of which can independently form a beam, simultaneously tracking one high-Earth orbit satellite and three neighboring low-Earth orbit satellites, realizing redundant backup of the high-Earth orbit and low-Earth orbit links.

[0044] High and low rail signal adaptation transmission protocol:

[0045] Polarization Adaptive Matching: For linearly polarized signals from high-orbit satellites and circularly polarized signals from low-orbit satellites, phase coordination control of liquid crystal phase shifters enables real-time conversion between circular and linear polarization, stabilizing the axial ratio within 3dB and reducing polarization loss to below 0.5dB; Inter-satellite Link Delay Compensation: Combining the propagation delay differences between high-orbit and low-orbit links, a delay compensation algorithm is embedded in the antenna baseband module. Phase pre-compensation eliminates phase differences caused by delay, ensuring synchronous signal reception. 3. Automatic Air Interface Calibration Mechanism: The phase-voltage curve calibration of the antenna channel is achieved using the phase state ergonomic method. By traversing the bias voltage states of all phase shifters, the phase response characteristics of each channel are extracted, a calibration coefficient table is generated, and the consistency deviation and temperature drift of the liquid crystal material are compensated to ensure that the beam pointing error and gain fluctuation are within 2dB within the temperature range of -55℃ to +85℃ of the satellite platform. Control Module Construction: A phase control board is developed based on FPGA, pre-stores high- and low-orbit satellite ephemeris data, and writes beam tracking algorithms and phase calibration programs.

[0046] Dynamic link calibration technology:

[0047] The system adopts an integrated architecture of "calibration signal source - power divider network - coupler - detector", and shares a substrate with the LCD phased array antenna feed network. Specific components and functions are as follows: Wideband calibration signal source: A Ka / Ku dual-mode calibration source based on a phase-locked loop (PLL) design, outputting a 19.5-26.0GHz continuous wave signal with a power fluctuation of 0.5dB and phase noise / Hz (1kHz frequency deviation), providing a unified phase reference for each channel; Equal amplitude and in-phase power divider network: A 3-stage 1-to-4 microstrip power divider divides the calibration signal source output signal into 16 equal amplitude and in-phase signals (amplitude...). The signal has an amplitude imbalance of <0.3dB and a phase imbalance of <0.1dB, and is fed into 16 antenna channels respectively. A directional coupler array is used: each channel integrates a 10dB directional coupler, with the coupling end connected to a detector to achieve amplitude and phase sampling of the RF signal. The main signal is fed into a liquid crystal phase shifter without loss, avoiding interference from the calibration link to the communication link. An amplitude and phase detection unit uses a dual-channel quadrature detector to convert the RF signal into an I / Q baseband signal with a sampling rate of 100MSps and a measurement accuracy of .1dB (amplitude) and (phase). The data is transmitted to the FPGA control unit via a high-speed serial port.

[0048] The calibration module and the liquid crystal phased array antenna are coplanarly integrated using a flexible printed circuit board (FPC), with an overall thickness of <0.8mm and a weight of <50mW, meeting the lightweight and low-power constraints of the satellite platform. Simultaneously, a polyimide heat insulation layer is coated on the module surface to ensure... Signal stability within the temperature range.

[0049] To address the inherent amplitude and phase deviation of antenna channels, an improved four-phase amplitude calibration method is employed for rapid reference calibration. The specific steps are as follows: Phase state configuration: Channel 1 is selected as the reference channel, and the remaining 15 channels are sequentially set to four phase states (0°, 90°, 180°, 270°), with the reference channel phase fixed at 0°; Amplitude data acquisition: The total received power of the channel under each phase state is acquired using a detector, generating four sets of amplitude datasets; Amplitude and phase parameter calculation: The amplitude datasets are fitted using the least squares method to calculate the inherent amplitude attenuation coefficient and phase offset of each channel, generating a channel reference calibration coefficient table. The calibration time is <20ms, and the phase calibration accuracy and amplitude calibration accuracy are 2dB, which is 16 times more efficient than the traditional rotating vector method.

[0050] To eliminate the influence of wide-temperature environments on liquid crystal phase shifters, a three-dimensional compensation model of liquid crystal dielectric constant-temperature-phase is established. The specific implementation method is as follows: Offline model training: Data is collected in a ground-based environmental simulation chamber. The phase-voltage response curve of the liquid crystal phase shifter within the range (step size 5℃) and the 0-360° phase interval was used to obtain the temperature compensation coefficient k through polynomial fitting. , (T is the phase, and T is the temperature); On-orbit real-time compensation: A miniature thermistor (temperature measurement accuracy ±0.5℃) is integrated into the antenna module to collect the operating temperature in real time. The FPGA control unit corrects the phase shifter bias voltage based on the temperature value and the pre-stored compensation coefficient, using the following formula: Where V0 is the voltage value corresponding to the target phase at room temperature (25℃), T0 is the room temperature reference, and Vcal is the calibrated voltage value. This algorithm can reduce the phase error caused by temperature from more than 5° to less than 1°.

[0051] To address the dynamic communication conditions of high and low Earth orbit (HEO) satellites, a joint calibration mechanism based on inter-satellite pilots is designed to adapt to the beam tracking requirements of high-speed moving HEO satellites. The specific process is as follows: Pilot signal design: Dedicated calibration pilots (accounting for 5% of frame resources) are embedded in HEO and HEO satellite communication frames. The pilots use QPSK modulation with a subcarrier spacing of 15kHz and carry antenna channel ID and phase reference information; Link phase calculation: After receiving the HEO satellite pilot signal, the HEO satellite extracts the pilot phase of each channel and, combined with the local calibration reference, calculates the propagation phase difference and beam pointing deviation of the inter-satellite link; Real-time phase correction: The link phase difference is compensated into the phase shifter control voltage to achieve dynamic beam pointing calibration and ensure the beam pointing error during HEO satellite transit.

[0052] Design a three-level calibration trigger logic to achieve adaptive calibration throughout the entire lifecycle:

[0053] Timed calibration: Trigger a full-channel reference calibration every 24 hours to update the calibration coefficient table and eliminate performance drift caused by device aging; Threshold-triggered calibration: When the thermistor detects a temperature change exceeding 5°C, or the detector detects a channel amplitude fluctuation exceeding 0.5dB / phase fluctuation exceeding 2°, automatically trigger temperature compensation calibration or channel reference calibration; Operating condition switching calibration: Trigger joint calibration of air interface pilot before high-orbit satellite beam switching (when the switching command is issued) and frequency band switching (Ka / Ku band switching) to ensure stable link performance after switching.

[0054] A calibration task scheduler is built based on FPGA, and calibration priorities are set (condition switching calibration > threshold trigger calibration > timed calibration). A time-division multiplexing mechanism is adopted to avoid conflicts between calibration tasks and communication tasks: high-priority calibration (condition switching / threshold trigger) occupies the pilot time slot of the communication frame (5% of the duration) without affecting the data transmission of services; low-priority calibration (timed calibration) is performed during satellite transit intervals (times without communication services), and the duration of a single calibration is <100ms, ensuring that it does not occupy effective communication resources.

[0055] Taking the on-orbit dynamic calibration of a 4×4 satellite-borne liquid crystal phased array antenna as an example, the implementation steps are as follows: Ground pre-calibration: Complete the channel reference calibration in the microwave anechoic chamber, generate the initial calibration coefficient table and write it into the FPGA storage unit; Complete the temperature-phase compensation model training in the environmental simulation cabin and obtain the compensation coefficients for the entire temperature range; On-orbit deployment: Carry the antenna payload with integrated calibration module to the low-orbit satellite and complete the joint debugging of on-board power supply and communication link;

[0056] Dynamic calibration execution: After the satellite enters orbit, the first timed full-channel calibration is triggered, updating the reference coefficients; when the satellite temperature rises from 25°C to 55°C, the thermistor triggers temperature compensation calibration, and the FPGA automatically corrects the phase shifter voltage, reducing the phase error from 4.2° to 0.8°; when the low-Earth orbit satellite switches to a high-Earth orbit relay satellite, the air interface pilot joint calibration is triggered, completing beam pointing correction within 5ms, reducing gain loss after link switching, and ensuring uninterrupted communication. A schematic diagram of the calibration process is shown below. Figure 1 .

[0057] Comparison table of phase errors before and after calibration of liquid crystal phased array high and low orbit satellite systems: Dynamic link calibration technology and on-orbit dynamic calibration, covering core scenarios such as temperature drift, inherent channel deviation, and inter-orbit switching, demonstrating the error correction effects of different calibration technologies.

[0058]

[0059] The beam switching time (time to switch from one beam pointing to another) test results for liquid crystal phased array antennas mainly fall within the millisecond range, with specific values ​​varying depending on the materials, structure, and test conditions. The mainstream test results are as follows:

[0060]

[0061] A schematic diagram of the beam switching process is shown below. Figure 2 Key influencing factors such as Figure 3 .

[0062] The rate of change of the dielectric constant of liquid crystal materials directly affects the phase shift capability and loss of phased array antenna elements. Simultaneously, the maximum value of the dielectric constant of the liquid crystal material influences the element size of the resonant unit. When an external electric field is applied, the orientation of the liquid crystal molecules deflects, and electrostatic energy is converted into elastic potential energy. When the liquid crystal molecules reach equilibrium, the actual arrangement and distribution of the liquid crystal molecules can be obtained by minimizing the Gibbs free energy. Using the Euler equation, combined with variational and differential iteration methods, a partial differential equation describing the distribution of the liquid crystal molecule orientation vectors within a certain space is obtained. From this, the corresponding liquid crystal refractive index can be calculated by the change in the distribution of the liquid crystal orientation vectors within the liquid crystal cell under different external electric field conditions. Modeling techniques for the Ka-band characteristics of liquid crystal materials include... Figure 4 .

[0063] The electromagnetic properties of liquid crystal materials were analyzed in detail using high-precision electromagnetic simulation software such as HFSS and CST. An optimization algorithm combining the finite element method and electromagnetic wave propagation was employed to accurately model and analyze the liquid crystal materials. The dielectric and loss models were derived by combining these methods with electromagnetic simulation. Anisotropic liquid crystal materials were simulated using HFSS software, and the dielectric and loss models of the anisotropic liquid crystals were verified and optimized in the Ka-band using resonant method numerical modeling, thereby reducing errors.

[0064] The initial parameters of the phase-shifting unit of the Ka-band liquid crystal phased array antenna were determined based on theoretical analysis, and a simulation model was established. Then, using the effective dielectric constant equivalent method, the equivalent dielectric constant corresponding to 360° phase shifting of the phase-shifting unit was simulated and calculated to optimize parameters such as unit size, insertion loss, bandwidth, and phase shift range. The liquid crystal phase-shifting unit model is shown below. Figure 5 .

[0065] The broadband radiating patch, as the front end of this antenna, plays a crucial role in its radiation characteristics. Antenna elements should possess wide impedance bandwidth and wide half-power beamwidth characteristics. Key indicators for evaluating the radiation characteristics of antenna elements include: impedance bandwidth, active scanning standing wave ratio (VSWR) of the array elements, radiation efficiency, and the radiation pattern of the array elements. Compared to traditional narrowband antennas, broadband antennas not only require a wider impedance bandwidth but also need good and stable performance across the entire broadband range to ensure limited gain loss during large-bandwidth, large-spatial scanning. This embodiment uses a patch slotting method to separate degenerate modes to achieve circular polarization, a stacked patch technique to extend the axial ratio bandwidth, and slot-coupled feeding and stacked patches to improve the impedance bandwidth. The broadband radiating element direction is as follows... Figure 6 .

[0066] Liquid crystal phased array antennas utilize the electrically controlled tuning properties of liquid crystals to achieve phase compensation for each array element. In practical antenna design, phase compensation of the control unit is controlled by applying different voltage signals to each liquid crystal element, thereby ensuring that each array element meets the required phase distribution. By studying the electromagnetic properties of liquid crystal materials, the interaction scanning mechanism between incident electromagnetic waves and liquid crystal materials is analyzed, as well as the response characteristics of incident electromagnetic waves after passing through the complex modulation effects of liquid crystal materials.

[0067] In practical antenna design, phase compensation of the control unit is achieved by applying different voltage signals to each liquid crystal cell, thereby ensuring that each array cell meets the required phase distribution. Therefore, we need to obtain the phase of the liquid crystal cells. The relationship with the applied bias voltage V, i.e. -V curve relationship. In electromagnetic simulation, different values ​​can be achieved simply by changing the dielectric constant of the liquid crystal in each element of the array. Value. Therefore, we need to obtain the phase of the cell. With the dielectric constant of liquid crystal The relationship between them, that is The relationship between the curves is analyzed to determine their modulation effect on the amplitude, phase, and frequency of electromagnetic waves. A theoretical model for beamforming and acquisition tracking methods is established, and the influence of their characteristic parameters on electromagnetic control is analyzed.

[0068] To achieve two-dimensional beam scanning, each liquid crystal phase-shifting unit must be independently phase-shifting controlled. This study investigates an independent driving circuit design method based on the existing driving control method of TFT-LCD panel production lines. A conductive non-metallic thin film is introduced into the liquid crystal structure as a wave-transparent ground electrode design. The impact of this driving circuit design on Ka-wave transmission and loss is analyzed.

[0069] Based on existing large-scale array driving designs for liquid crystal antennas, a large-scale array driving circuit based on TFT technology was designed to meet the requirements of this project. This achieves simple and efficient driving control of metamaterial structure antenna elements, significantly reducing panel manufacturing costs and improving the integration of reconfigurable phased array antennas. It successfully solves the technological challenges of existing antenna designs that rely on direct wiring or vias in the dielectric substrate for connection to the driving circuit. Furthermore, the row-column matrix driving method greatly simplifies the complexity of the driving circuit, improves response speed, and makes it possible to drive more antenna elements. This enables the manufacture of large-size reconfigurable liquid crystal phased array antennas. Including the liquid crystal response time, the overall beam switching time of the phased array antenna is <25ms. The large-scale array driving circuit design is as follows: Figure 7 .

[0070] The phase-shifting unit of a liquid crystal phased array antenna can be considered as an analog phase shifter. As long as the driving voltage gradient is controlled sufficiently small, the phase-shifting accuracy of each unit can be controlled to a sufficiently high level. In this project, when the beam control chip uses analog output, our unit has verified that it supports the liquid crystal phase shifter bias driving voltage being precisely discretized into 256 states, which is equivalent to an 8-bit digital phase shifter. The phase-shifting accuracy of each unit is 1.4°, meeting the requirement of tracking accuracy better than 1 / 8 half-power beamwidth. The high-precision phase shifter precise control technology approach is as follows... Figure 8 .

[0071] Optimal multibeamforming algorithm for liquid crystal analog and digital hybrid systems:

[0072] The ability to form multiple beams using a direct-radiating array antenna is a major advantage of phased array antennas. The key to achieving multiple beams in a liquid crystal phased array antenna is constructing a beamforming network. Its output port and the antenna elements in the array are controlled by different liquid crystal phase shifters to achieve different phase distributions, thereby generating beams with different directions. Liquid crystal phased array antennas can achieve both analog and digital beamforming.

[0073] In traditional phased array antennas, beamforming typically employs analog beamforming, with multi-beaming usually performed at radio frequency (RF). With analog beamforming, once the beamforming network scheme is determined, the beam shape, intersection levels of adjacent beams, and beam pointing are fixed and difficult to modify. This is especially true when the number of beams to be formed is large, making hardware implementation extremely complex and difficult to adjust; forming low-sidelobe multi-beams or achieving adaptive beam pointing or null control becomes even more challenging. In the past decade or so, with the rapid development of phased array technology, the use of digital technology for beamforming has received widespread attention. Digital beamforming technology is a spatial filtering technique resulting from the combination of modern digital signal processing technology and array antenna technology. Compared to analog beamforming, digital beamforming offers a series of advantages, including easy implementation of multi-beams, extremely low sidelobe levels, beam pointing control or beam reconstruction based on changes in coverage area, flexible switching over a wide scanning angle range, power allocation between beams, convenient channel amplitude and phase error correction, and adaptive interference nulling. Currently, the DBF system has begun to be applied to large communication satellites in geostationary orbit. However, simply adopting a digital beamforming scheme will also lead to a sharp increase in the complexity and cost of hardware design and multi-beamforming algorithms, which is also a major challenge for low-Earth orbit satellite on-board antennas.

[0074] Wave position phase pre-storage and parallel control architecture:

[0075] Phase table preloading module: Based on satellite ephemeris data, the voltage-phase mapping relationship of phase shifters corresponding to typical positions of adjacent satellites within the low-Earth orbit constellation and high- and low-Earth orbit satellites is calculated in advance on the ground, generating an inter-orbit phase table (containing 128 typical positions, covering a ±45° scanning range), and storing it in the on-chip ROM of the antenna FPGA. Each position in the phase table corresponds to the voltage configuration value of 16-channel phase shifters with an accuracy of 0.01V, enabling continuous phase adjustment from 0-360°.

[0076] Parallel Phase Drive Unit: Employing a 16-channel high-voltage DAC array (output voltage range 0-20V, conversion rate 1MSps), this unit replaces the traditional channel-by-channel serial control method, enabling parallel voltage loading of 16 liquid crystal phase shifters. Each DAC channel is directly connected to the phase shifter's bias terminal. Voltage commands from the phase table are synchronously sent via the FPGA, compressing the beam switching phase adjustment time from 50ms in serial mode to less than 8ms. Furthermore, power fluctuations in dB during switching are minimized, preventing far-field beam flicker.

[0077] Wave position rapid identification module: integrates onboard GNSS and orbit calculation unit, calculates the relative azimuth angle between the current satellite and the target satellite in real time (measurement accuracy 1°), and matches the optimal wave position in the phase table within 1ms through azimuth angle-wave position index mapping algorithm, triggering parallel phase adjustment.

[0078] Wide-angle scan gain compensation hardware design:

[0079] To address the gain loss issue caused by wide-angle scanning (±45°) of the inter-track beam, a dielectric resonator compensation unit is integrated into the radiating layer of the liquid crystal phased array antenna, with each radiating unit loaded with a high dielectric constant. The dielectric resonator, through the resonance enhancement effect, reduces the gain loss during ±45° scanning from more than 3dB in the traditional scheme to less than 1.2dB, ensuring stable link receiving power after inter-rail beam switching.

[0080] Inter-orbit Doppler frequency offset dual-mode compensation algorithm:

[0081] To address the Doppler frequency offset (maximum 340kHz) caused by the high dynamic range of low-Earth orbit satellites, a PLL-FFT-VV dual-mode switching algorithm is designed to achieve accurate frequency offset compensation across the entire dynamic range. The specific steps are as follows:

[0082] Dynamic scene recognition: By monitoring the link carrier phase change rate Determine the dynamic level between orbits: When the phase change rate is rad / s (low dynamic, such as interconnection between satellites in the same orbit and low orbit), enable the PLL closed-loop compensation mode; when the phase change rate is >50rad / s (high dynamic, such as interconnection between high and low orbits), switch to the FFT-VV open-loop compensation mode.

[0083] PLL closed-loop compensation: A third-order phase-locked loop is used, with adaptive loop bandwidth adjustment (100Hz-1kHz). The carrier phase error is detected in real time by a phase detector, and the output control voltage is driven by the loop filter to drive the voltage-controlled oscillator to compensate for frequency deviation. The root mean square error (NRMSE) of frequency deviation is estimated in low dynamic scenarios. Phase fluctuation is 0.4 rad. FFT-VV open-loop compensation: First, a coarse frequency offset estimate is performed on the received signal using a 1024-point FFT (acquisition range ±500kHz, estimation time). Then, a fine phase compensation is performed using the VV algorithm (Viterbi-Viterbi). In high dynamic range scenarios, the NRMSE is stabilized at... This ensures that the carrier synchronization accuracy meets the requirements of inter-orbit communication.

[0084] Link quality-driven parameter adaptation algorithm:

[0085] Based on link quality metrics such as signal-to-noise ratio (SNR), bit error rate (BER), and received power, adaptive adjustment of parameters in three dimensions is achieved:

[0086] Polarization adaptive matching: Real-time monitoring of link polarization loss (measured with an axial ratio tester, accuracy .1dB). When polarization loss > 2dB, the FPGA automatically adjusts the phase configuration of the phase shifters, switching between linear and circular polarization modes. For example, when a high-orbit satellite is a linearly polarized signal, the antenna radiation mode is switched from left-hand circular polarization to linear polarization through phase coordination of four adjacent phase shifters (0° / 90° / 180° / 270°), reducing polarization loss to within 0.5dB.

[0087] Adaptive band switching: Based on the dual-mode antenna architecture of Ka-band (25.5-26.0GHz) and Ku-band (19.5-20.5GHz), a link quality threshold (SNR 0dB triggers switching) is set. When the Ka-band link is affected by rain attenuation / ionospheric scintillation, the RF switch of the feed network is switched (the switching time automatically switches to the Ku-band, and the corresponding frequency band phase compensation coefficient is applied to ensure that the link SNR recovers to above 15dB).

[0088] Power adaptive allocation: Based on link distance and propagation loss, the radiated power is continuously adjustable from 0-3dB by adjusting the driving voltage of the liquid crystal phase shifter (changing the equivalent dielectric constant). For example, when communicating with high-orbit satellites (link distance > 35000km), the radiated power is automatically increased by 3dB to compensate for long-distance path loss; when communicating with nearby low-orbit satellites, the power is reduced to minimize interference. The link adaptive control logic is as follows: Figure 9 .

[0089] Switching to an adapted linkage triggering mechanism:

[0090] The design incorporates a linkage logic of "beam switching pre-trigger + link adaptation parallel execution". The specific process is as follows: when the current satellite link SNR is detected to be lower than the threshold or the target satellite enters the communication range, a beam switching pre-command is issued 5ms in advance, and the FPGA pre-reads the phase configuration of the target beam position.

[0091] Within the 8ms window of beam switching, the link adaptation algorithm is started synchronously: the first 2ms completes the coarse compensation of Doppler frequency offset, the middle 4ms completes the polarization / frequency band matching, and the last 2ms completes the power calibration.

[0092] When beam switching is completed, link adaptation synchronization ends, and the link interruption time is reduced from more than 100ms to less than 10ms, achieving seamless inter-rail switching.

[0093] Multi-objective priority scheduling algorithm:

[0094] For scenarios where a low-Earth orbit satellite simultaneously establishes links with multiple satellites (1 high-Earth orbit relay satellite + 3 low-Earth orbit constellation satellites), a weighted priority algorithm is used to dynamically allocate beam and link resources:

[0095] Priority weight settings: High-orbit relay link (weight 0.7) > Low-orbit backbone link (weight 0.5) > Low-orbit access link (weight 0.3). The weight is strongly correlated with the link service priority (high priority is emergency communication / backbone data, low priority is ordinary measurement and control).

[0096] Beam Time Division Multiplexing: Employing a TDMA mechanism, 70% of the beam dwell time is allocated to high-priority links, while low-priority links share the remaining 30%. Simultaneously, fast beam switching (8ms / time) enables time-division interconnection of multiple target links, ensuring that the BER of high-priority links is <10^-6, and low-priority links... .

[0097] Taking the inter-orbit handover between low-Earth orbit satellites and high-Earth orbit relay satellites as an example, the implementation steps are as follows:

[0098] Ground pre-configuration: Generate a typical high and low orbit wave phase table (containing 64 high and low orbit wave positions) on the ground and write it into the FPGA ROM; complete the PLL-FFT-VV dual-mode algorithm parameter calibration and store it in the algorithm module;

[0099] On-orbit monitoring: When the low-orbit satellite communicates with the original low-orbit backbone satellite, the link monitoring unit detects that the SNR drops to 8dB (below the 10dB threshold), and at the same time, the high-orbit relay satellite enters the communication range (azimuth angle 35°).

[0100] Cooperative handover:

[0101] Within 1ms, the FPGA matches the high and low orbit positions corresponding to 35°, sends out parallel phase commands, and completes beam switching in 8ms.

[0102] During the switching window, the FFT-VV algorithm is started simultaneously (because the high and low orbits are high dynamic scenarios), 320kHz Doppler frequency offset compensation is completed in 2ms, switching to the Ka band and completing circular polarization-linear polarization matching is completed in 4ms, and the radiated power is increased by 3dB in 2ms.

[0103] After the handover was completed, the link SNR recovered to 16dB, and the BER dropped to 16dB. The link interruption time is only 9ms, achieving seamless interconnection.

[0104] Example 2

[0105] according to Figure 1 , 2As shown in Figures 3, 4, 5, 6, 7, 8, and 9, this embodiment proposes a high-Earth orbit (LEO) and low-Earth orbit (LEO) satellite signal switching and calibration system and method based on a liquid crystal phased array. This system is applied to a collaborative communication scenario between a LEO satellite constellation and a high-Earth orbit (LEO) relay satellite. The system configuration is as follows:

[0106] The liquid crystal phased array antenna module adopts a 4×4 array architecture, containing 16 liquid crystal phase shifting units. The phase shift accuracy of a single unit is 1.4°, the antenna panel thickness is <0.8mm, the weight is <50mW, and the surface is coated with a polyimide heat insulation layer. The beam control module uses an XC7K325T FPGA, pre-stores 64 typical high and low orbit phase tables (covering a ±45° scanning range), integrates a GNSS orbit calculation unit, and has an azimuth measurement accuracy of ±1°. The dynamic calibration module includes a Ka / Ku dual-mode PLL calibration signal source (output 19.5-26.0GHz), a 3-level 1-to-4 microstrip power divider network, 16 10dB directional couplers, and dual-channel orthogonal detectors (sampling rate 100MSps). The link adaptation module integrates a PLL-FFT-VV dual-mode compensation algorithm and a polarization / band switching control unit.

[0107] The workflow is as follows:

[0108] Pre-configuration phase: Channel reference calibration is completed in a terrestrial microwave anechoic chamber, generating an initial calibration coefficient table; configuration is completed in an environmental simulation chamber. The full-temperature-range temperature compensation model is trained, and the compensation coefficient k is obtained. All of the above data is written into the FPGA storage unit.

[0109] During operation in orbit, when low-Earth orbit satellites communicate with other low-Earth orbit constellation satellites, the link monitoring unit detects the SNR in real time. When the SNR drops to 8dB (below the 10dB threshold) and a high-Earth orbit relay satellite enters the communication range (azimuth angle 35°), the handover process is triggered.

[0110] The beam control module matches the beam position parameters corresponding to 35° within 1ms, and sends voltage commands in parallel through a 16-channel high-voltage DAC array, completing the switch of the beam from low-Earth orbit satellite to high-Earth orbit satellite within 8ms.

[0111] During the switching window, the dynamic calibration module triggers joint calibration of the air interface pilot, calculates the link phase difference using the QPSK modulated pilot signal (occupying 5% of the frame resources), and completes beam pointing correction within 5ms; at the same time, the link adaptation module starts the FFT-VV algorithm, completes 320kHz Doppler frequency offset compensation within 2ms, achieves circular polarization to linear polarization conversion within 4ms, and increases radiated power by 3dB within 2ms;

[0112] After the handover was completed, the link SNR recovered to 16dB, and the BER dropped to 16dB. The phase error is 0.8° and the link interruption time is 9ms.

[0113] This invention replaces traditional mechanical scanning antennas and gallium arsenide phased array antennas with liquid crystal phased array antennas, achieving millisecond-level beam switching through inertial-free electronic scanning. It also supports multi-beam generation capability for multiple satellites accessed from a single point, significantly simplifying the terminal architecture and reducing equipment size, weight, and power consumption. This solves the pain points of traditional equipment, such as large switching delays and limited deployment, and is suitable for various application scenarios including spaceborne and vehicle-mounted systems. Furthermore, this invention features an integrated dynamic calibration module and multi-dimensional calibration algorithms. Through power-on self-calibration, online background calibration, and a three-level triggered calibration mechanism, it achieves comprehensive compensation for channel amplitude and phase deviation, temperature drift, and inter-orbit link phase difference. The phase error after calibration is <1°, eliminating reliance on complex external calibration equipment, reducing maintenance costs, and improving long-term system stability, making it compatible with satellite platforms. It provides a wide operating temperature range. Simultaneously, this invention constructs a collaborative mechanism of beam switching, dynamic calibration, and link adaptation. Through strategies such as beam pre-configuration, Doppler dual-mode compensation, and adaptive adjustment of polarization / frequency band / power, it effectively addresses issues such as latency differences and frequency offset interference caused by the heterogeneous characteristics of high and low orbits. Link interruption time is reduced to less than 10ms, and polarization loss is ≤0.5dB, significantly improving the seamlessness and anti-interference capability of high and low orbit collaborative communication, and ensuring the transmission quality of real-time voice, video conferencing, and other services.

[0114] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high- and low-orbit satellite signal switching and calibration system based on a liquid crystal phased array, comprising a liquid crystal phased array antenna module, a beam control module, a dynamic calibration module, and a link adaptation module, characterized in that: The liquid crystal phased array antenna module is used to receive and transmit high and low orbit satellite signals. It contains several independently controllable liquid crystal phase shifting units and achieves inertial-free electronic scanning and multi-beam generation through voltage regulation. The beam control module is connected to the liquid crystal phased array antenna module and pre-stores high and low orbit satellite ephemeris data and typical wave position phase table. It is used to calculate the relative azimuth angle of the satellite in real time and output beam pointing control commands. The dynamic calibration module is integrated into the liquid crystal phased array antenna module and includes a calibration signal source, a power divider network, a coupler array, and an amplitude and phase detector unit. It is used to realize antenna channel amplitude and phase reference calibration, temperature-phase drift compensation, and air interface pilot joint calibration. The link adaptation module is linked with the beam control module and the dynamic calibration module to realize polarization mode matching, inter-satellite delay compensation, Doppler frequency offset correction, and adaptive adjustment of frequency band and power. The beam control module triggers the liquid crystal phased array antenna module to complete high-Earth orbit and low-Earth orbit beam switching through a parallel phase driving mechanism. The dynamic calibration module compensates for link errors in real time, and the link adaptation module synchronously optimizes transmission parameters, achieving seamless switching and stable transmission of high-Earth orbit and low-Earth orbit satellite signals. The liquid crystal phased array antenna module adopts a 4×4 array architecture, and the liquid crystal phase shifting unit is based on nematic liquid crystal material, with a single unit phase shifting accuracy ≥ ,support Continuous phase modulation allows the antenna panel to simultaneously generate at least one high-orbit directional beam and three low-orbit directional beams through zoned control. The dynamic calibration module adopts an integrated architecture of calibration signal source-power divider network-coupler-detector, sharing a substrate with the LCD phased array antenna feed network. The overall thickness is <0.8mm and the weight is <50mW. The calibration signal source is a Ka / Ku dual-mode phase-locked loop signal source with an output frequency range of 19.5-26.0GHz. The beam control module is built on an FPGA chip and integrates an orbit parameter calculation unit, a beam position fast identification unit, and a parallel phase drive unit. The parallel phase drive unit uses a 16-channel high-voltage DAC array with an output voltage range of 0-20V and a conversion rate ≥1MSps, achieving synchronous voltage loading of 16 phase shifters.

2. A method for switching and calibrating high- and low-Earth orbit satellite signals based on a liquid crystal phased array, employing the high- and low-Earth orbit satellite signal switching and calibration system based on a liquid crystal phased array as described in claim 1, characterized in that... Includes the following steps: S1: Pre-configuration stage: Obtain orbital parameters and ephemeris data of high and low orbit satellites, calculate the phase shifter voltage-phase mapping relationship corresponding to typical wave positions, generate inter-orbit wave position phase table and initial values ​​of calibration coefficients, and store them in the beam control module. S2: Dynamic beam tracking and switching. The beam control module calculates the relative azimuth angle of the satellite in real time, matches the optimal beam position, and controls the liquid crystal phased array antenna module through a parallel phase drive mechanism to achieve millisecond-level beam pointing adjustment and complete the high- and low-orbit satellite link switching. S3: Multi-dimensional dynamic calibration, based on a three-level calibration triggering mechanism, uses channel amplitude and phase reference calibration, temperature-phase drift compensation and air interface pilot joint calibration algorithm to correct antenna channel error and link phase deviation in real time; S4: Link parameter adaptive adaptation. The link adaptation module monitors link quality indicators and dynamically adjusts polarization mode, transmission frequency band, radiated power and Doppler frequency offset compensation parameters to ensure link stability after handover. Steps S2-S4 are executed in parallel to achieve coordinated switching and calibration of high and low orbit satellite signals.

3. The method for switching and calibrating high and low orbit satellite signals based on a liquid crystal phased array according to claim 2, characterized in that: In S2, the beam switching adopts a pre-trigger-parallel control mechanism. When the current link signal-to-noise ratio is detected to be lower than the threshold or the target satellite enters the communication range, the target beam phase configuration is pre-read 5ms in advance, and the beam switching time is <10ms.

4. The method for switching and calibrating high and low orbit satellite signals based on a liquid crystal phased array according to claim 2, characterized in that: In S3, the three-level calibration triggering mechanism includes timed calibration, threshold-triggered calibration, and operating condition switching calibration. The timed calibration cycle is 24 hours, and the temperature change exceeds... Or channel amplitude fluctuation exceeds 0.5dB / phase fluctuation exceeds Threshold calibration is triggered at certain times, and operating condition switching calibration is triggered before high / low rail switching or frequency band switching.

5. The method for switching and calibrating high and low orbit satellite signals based on a liquid crystal phased array according to claim 4, characterized in that: In S3, the temperature-phase drift compensation is based on a three-dimensional model of liquid crystal dielectric constant-temperature-phase, and the phase shifter bias voltage is corrected using the following formula: ， Where Vcal is the calibrated voltage value, V0 is the room temperature reference voltage, k is the temperature compensation coefficient, T is the real-time temperature, T0 is the room temperature reference value, and the calibrated phase error is < .

6. The method for switching and calibrating high and low orbit satellite signals based on a liquid crystal phased array according to claim 2, characterized in that: In step S4, the Doppler frequency offset compensation employs a PLL-FFT-VV dual-mode algorithm. PLL closed-loop compensation is enabled for low-dynamic scenarios, while FFT-VV open-loop compensation is switched for high-dynamic scenarios. The root mean square error of the frequency offset estimation is ≤ .

7. The method for switching and calibrating high and low orbit satellite signals based on a liquid crystal phased array according to claim 6, characterized in that: In S4, the polarization mode adaptation achieves real-time switching between circular and linear polarization through phase coordination control of the liquid crystal phase shifter, with the axial ratio stabilized within 3dB and the polarization loss reduced to below 0.5dB.

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