Spaceborne laser terminal analog test equipment and method for multiple rate regimes

Abstract

The application belongs to the technical field of laser communication, and particularly relates to a satellite-borne laser terminal analog test device and method for multiple rate systems. The device comprises: a CPU main control module for being responsible for overall system control and collection and processing of test data; a clock module for providing multiple clock signal outputs to ensure synchronization of the system under different rates; a digital interface module for low-speed data communication, supporting multiple interfaces, and performing data processing through an FPGA chip; a digital processing module for being responsible for high-speed data processing, performing signal modulation and demodulation, and realizing complex digital signal processing through the FPGA chip; and an optical front-end module for transmitting and receiving laser signals, and simulating Doppler frequency offset and signal attenuation. The application has the characteristics of significantly improving the universality and flexibility of the device, being capable of meeting the test requirements of different types of laser terminals, and reducing the development and maintenance costs of the device.

Description

Technical Field

[0001] This invention belongs to the field of laser communication technology, specifically relating to a simulation test device and method for spaceborne laser terminals for various rate systems. Background Technology

[0002] With the rapid development of satellite laser communication technology, onboard laser terminals must undergo functional integrity verification before satellite launch. Since different models of onboard laser terminals have different laser rates and wavelengths, ground-based testing equipment needs to be flexibly adapted to these terminals. Existing ground-based laser communication simulation equipment is typically designed for specific laser terminal models, and the testing equipment can only meet the testing requirements of that model. Designing dedicated testing equipment for each model not only increases development costs but also significantly increases the difficulty of equipment maintenance and operation.

[0003] Existing testing equipment typically lacks modular design and configuration flexibility when handling laser communication requirements at various rates. Therefore, the testing of multi-rate, multi-system laser terminals suffers from low testing efficiency, poor equipment versatility, and difficulty in covering the diverse needs of different terminals.

[0004] Therefore, it is very important to design a ground simulation device that can adapt to different types of spaceborne laser terminals and multiple rate systems. Summary of the Invention

[0005] This invention aims to overcome the problems of rate system incompatibility and poor equipment versatility in existing equipment for ground testing of laser communication terminals. It provides a spaceborne laser terminal simulation test equipment and method for multiple rate systems, which adopts a modular design and divides the test requirements into different functional modules of the ground simulation equipment to achieve multi-system laser communication terminal testing.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] Spaceborne laser terminal simulation and testing equipment for various rate systems includes:

[0008] The CPU main control module is responsible for the overall system control and the collection and processing of test data;

[0009] The clock module is used to provide multiple clock signal outputs to ensure system synchronization at different speeds;

[0010] The digital interface module is used for low-speed data communication, supports multiple interfaces, and performs data processing through an FPGA chip.

[0011] The digital processing module is responsible for high-speed data processing, signal modulation and demodulation, and complex digital signal processing through the FPGA chip.

[0012] The optical front-end module is used for transmitting and receiving laser signals and to simulate Doppler frequency shift and signal attenuation.

[0013] Preferably, the CPU main control module includes a CPCI motherboard; the CPCI motherboard is equipped with an SSD solid-state drive and DDR3 memory; the CPCI motherboard is also equipped with external interfaces; the external interfaces include a Gigabit Ethernet interface and a USB 2.0 / 3.0 interface.

[0014] Preferably, the CPU main control module also includes a keyboard, mouse, and display device to provide a UI interface; the UI interface is used to enable users to perform human-computer interaction and complete corresponding operations.

[0015] Preferably, the clock module is equipped with a DIP switch; the DIP switch is used to switch between internal and external clocks; when the DIP switch is set to 0, it is the internal clock; when the DIP switch is set to 1, it is the external clock; wherein, the internal clock is a high-stability clock of 10MHz, and the external clock is a clock source of any frequency.

[0016] Preferably, the digital interface module communicates with the CPU main control module via an Ethernet port; the digital interface module includes an FPGA management module, a 422 communication interface module, an LVDS interface module, an Ethernet control module, and a Flash module; the 422 communication interface module, the LVDS interface module, the Ethernet control module, and the Flash module are all communicatively connected to the FPGA management module; the digital interface module manages the 1PPS synchronization signal and realizes telemetry and remote control communication through the FPGA management module.

[0017] Preferably, the digital processing module includes two FPGA processing modules, an optical signal coherent receiving module, and an AD / DA module; the two FPGA modules are FPGA_0 module and FPGA_1 module, respectively.

[0018] The FPGA_0 module uses an internal FPGA hard core to implement communication between the PCIE interface and the CPU main control module for transmitting data core control information; the FPGA_0 module completes the timing control of the high-speed interface with the satellite platform through a high-speed interface chip; the FPGA_0 module is connected to the FPGA_1 module through an SRIO interface to realize dynamic loading of the program of the FPGA_1 module.

[0019] The FPGA_1 module is used to perform complex signal processing functions, including signal modulation, demodulation, and encoding / decoding.

[0020] The AD / DA module is used for analog-to-digital / digital-to-analog conversion of signal modulation and demodulation;

[0021] The optical signal coherent receiving module is electrically connected to the AD / DA module.

[0022] Preferably, the optical front-end module includes a bias controller, a modulator, an optical attenuator, a beam splitter, an optical amplifier, and an optical filter;

[0023] The beam splitter feeds the split signal light to the bias controller to control the modulator's operation;

[0024] The optical attenuator is used to prevent damage to the spaceborne laser terminal caused by excessive optical power between the system and the spaceborne laser terminal.

[0025] The optical amplifier is used to make the input power of the back-end demodulation reach a set threshold.

[0026] The optical filter is used to filter out noise and equalize the gain of the amplified signal light.

[0027] This invention also provides a method for simulating and testing spaceborne laser terminals for various rate systems, comprising the following steps:

[0028] S1, Multi-rate laser communication modulation

[0029] Test data is transmitted from the CPU main control module to the digital processing module via the PCIe bus; the digital processing module resamples the data according to the preset communication rate and adjusts the data rate through interpolation and decimation techniques.

[0030] The data stream is framed and scrambled at a set rate. The encoded data is converted from electrical signal to optical signal by the optical front-end module and then transmitted to the onboard laser terminal.

[0031] S2, Multi-mode laser communication demodulation

[0032] The optical signal received by the test system is first processed by the optical front-end module; after the optical signal is converted into an electrical signal, it is converted into an analog-to-digital signal by the ADC in the AD / DA module; the system then identifies the modulation format of the electrical signal according to the preset communication protocol, and selects coherent or incoherent processing mode based on the identification result; the coherent processing process includes carrier acquisition, matched filtering, symbol synchronization, carrier tracking and frame synchronization, followed by decoding, descrambling and deframe processing;

[0033] S3, Doppler frequency offset simulation

[0034] The user software calculates the distance delay and Doppler frequency offset information to be simulated based on the relevant parameters of inter-satellite motion; the relevant parameters include the satellite's relative position, velocity vector, signal frequency, propagation delay, observation angle, timestamp, and orbital parameters;

[0035] The calculated analog information is transmitted to the optical front-end module as control information. The optical front-end module performs frequency offset compensation and signal attenuation control to ensure that the signal adjustment meets expectations.

[0036] The simulated laser signal is split into beams by a beam splitter for real-time monitoring of the optical signal status.

[0037] Compared with the prior art, the beneficial effects of this invention are: (1) The laser communication ground simulation equipment of this invention adopts CPCI architecture and realizes support for laser communication tasks and interface link testing tasks of multiple rates and multiple systems through modular design; the equipment covers high-speed laser communication technology with multiple rates, including modulation and demodulation technology of multi-rate laser communication, realizing comprehensive coverage of testing requirements under different communication rates, and can meet the testing requirements of various spaceborne laser terminals; (2) This invention significantly improves the versatility and flexibility of the equipment, can meet the testing requirements of different types of laser terminals, reduces the equipment development and maintenance costs, and has broad application prospects. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of an architecture of the CPU main control module in this invention;

[0039] Figure 2 This is a schematic diagram of an architecture of the digital interface module in this invention;

[0040] Figure 3 This is a schematic diagram of an architecture of the digital processing module in this invention;

[0041] Figure 4 This is a schematic diagram of the signal flow of the optical front-end module in this invention. Detailed Implementation

[0042] To more clearly illustrate the embodiments of the present invention, specific implementation methods will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0043] This invention provides a spaceborne laser terminal simulation and testing device for various rate systems, comprising:

[0044] The CPU main control module is responsible for the overall system control and the collection and processing of test data;

[0045] The clock module is used to provide multiple clock signal outputs to ensure system synchronization at different speeds;

[0046] The digital interface module is used for low-speed data communication, supports multiple interfaces (422, LVDS, Ethernet, etc.), and performs data processing through an FPGA chip.

[0047] The digital processing module is responsible for high-speed data processing, signal modulation and demodulation, and complex digital signal processing through the FPGA chip.

[0048] The optical front-end module is used for transmitting and receiving laser signals, and simulates Doppler frequency shift and signal attenuation to ensure the signal quality of the laser link.

[0049] Through the flexible combination of the above modules, this invention can realize laser communication modulation and demodulation under multiple systems, and is suitable for various rates and testing tasks of spaceborne laser terminals.

[0050] Furthermore, such as Figure 1 As shown, the CPU main control module is a traditional CPCI motherboard, with a computer CPU as the core chip. It is equipped with a large-capacity, high-performance SSD solid-state drive and high-performance DDR3 memory. External interfaces support Gigabit Ethernet and USB 2.0 / 3.0 interfaces, allowing for the expansion of device capacity by connecting external large-capacity USB storage devices. A keyboard, mouse, display device, and UI interface are provided, allowing users to interact with the system and operate it. Its main functions include configuring and testing the entire system, including monitoring the system's status, sending and receiving telemetry and remote control commands, receiving link test data in real time and comparing it to disk, and generating local data sources for sending and receiving to test link performance.

[0051] Furthermore, the clock module includes a DIP switch; this switch enables switching between internal and external clocks. When the switch is set to 0, it operates as the internal clock; when set to 1, it operates as the external clock. The internal clock is a highly stable 10MHz clock, while the external clock is a clock source of any frequency. Through these settings, the clock module can simultaneously output three clock signals to meet the synchronization requirements of multi-rate laser communication.

[0052] Furthermore, such as Figure 2As shown, the digital interface module adopts an FPGA-based main processing architecture to realize low-speed data communication. It mainly consists of an FPGA management module, a 422 communication interface module, an LVDS interface module, an Ethernet control module, and a Flash module. It mainly completes the management of 1PPS, the telemetry and remote control communication function based on the 422 interface, the measurement and control communication function, and the communication of low-speed interfaces such as the CAN bus. It communicates with the CPU main control module through the Ethernet port.

[0053] Furthermore, such as Figure 3 As shown, the digital processing module includes two FPGA processing modules, an optical signal coherent receiving module, and an AD / DA module; the two FPGA modules are FPGA_0 module and FPGA_1 module, respectively.

[0054] The FPGA_0 module uses the internal hard core of the FPGA to realize communication between the PCIe interface and the CPU main control module for transmitting data core control information; it completes the timing control of the high-speed interface with the satellite platform through a high-speed interface chip; and it connects to the FPGA_1 module through the SRIO interface to realize dynamic loading of the program for the FPGA_1 module.

[0055] The FPGA_1 module is used to perform complex signal processing functions, including signal modulation, demodulation, and encoding / decoding.

[0056] The AD / DA module is used for analog-to-digital / digital-to-analog conversion of signal modulation and demodulation. The DAC converts the signal after BPSK mapping into a digital-to-analog converter to obtain a baseband modulated signal output, which is then sent to the laser modulator to obtain a laser modulated signal. The demodulation end converts the input laser modulated signal to baseband through the laser local oscillator to obtain I and Q baseband complex signals, which are then sampled by the ADC.

[0057] The optical signal coherent receiving module is electrically connected to the AD / DA module.

[0058] Furthermore, such as Figure 4 As shown, the optical front-end module includes a bias controller, a modulator, an optical attenuator, a beam splitter, an optical amplifier, and an optical filter;

[0059] The beam splitter feeds the split signal light to the bias controller to control the modulator's operation;

[0060] The optical attenuator is used to prevent damage to the spaceborne laser terminal caused by excessive optical power between the system and the spaceborne laser terminal.

[0061] The optical amplifier is used to make the input power of the back-end demodulation reach a set threshold.

[0062] The optical filter is used to filter out noise and equalize the gain of the amplified signal light.

[0063] The optical front-end module needs to perform the functions of transmitting and receiving BPSK optical signals, as well as detecting the status of optical transmission and reception. To ensure the stable operation of the modulator, the optical front-end module requires a beam splitter to split the signal light and supply it to the bias controller for modulator operation. An optical attenuator is used to prevent damage to the onboard laser terminal due to excessive optical power. A beam splitter detector is configured before the modulated light output port to detect the transmitted signal power. An optical amplifier is used to ensure that the input power for demodulation reaches a certain threshold. The signal light experiences spontaneous emission noise during amplification after passing through the optical amplifier; an optical filter is needed to filter out this noise and equalize the gain. The beam splitter divides the received signal light into two equal parts, facilitating real-time monitoring of the received signal status. The main functions of the transmission and reception links are as follows:

[0064] 1. Modulation and conversion of electrical signals to optical signals. The DA unit on the digital processing board connects the encoded and mapped electrical signal to the optoelectronic front-end module via a cable. The modulation driver on the optoelectronic front-end module amplifies the electrical signal and inputs it to the modulator to modulate it into an optical signal. After attenuation by the optical attenuator, the optical signal that meets the user's settings is sent to the communication terminal under test. After EDFA and optical filter processing, the received optical signal is input to the coherent receiver on the digital processing board.

[0065] 2. Doppler frequency offset and attenuation control of the transmitted optical signal. The user software calculates the required simulated distance delay, Doppler frequency offset, amplitude attenuation, and other information based on inter-satellite motion, and transmits the necessary control information via the digital processing module. The optoelectronic front end then completes the main part of the Doppler frequency offset simulation and attenuation simulation. Because the Doppler frequency offset in inter-satellite communication is relatively large, frequency offset compensation is required for the received optical signal.

[0066] Specifically, the present invention also provides a method for simulating and testing spaceborne laser terminals for various rate systems, comprising the following steps:

[0067] S1, Multi-rate laser communication modulation

[0068] Test data is transmitted from the CPU main control module to the digital processing module via the PCIe bus; the digital processing module resamples the data according to the preset communication rate and adjusts the data rate through interpolation and decimation techniques.

[0069] The data stream is framed and scrambled at a set rate. The encoded data is then converted from electrical to optical signals by the optical front-end module and transmitted to the onboard laser terminal. The entire modulation process consists of the following detailed steps:

[0070] Step S11: Obtain test data

[0071] The CPU main control module or high-speed data interface module first acquires the user's test data, and then transmits the data to the digital processing module to prepare for subsequent modulation.

[0072] Step S12: Data Resampling

[0073] The digital processing module selects appropriate interpolation and decimation coefficients based on a preset communication rate to resample the data. The resampled data stream is then adjusted according to the communication rate to adapt to the requirements of laser communication systems with different rates.

[0074] Step S13: Framing and Scrambling

[0075] During the framing process, the code data stream is framed according to a preset protocol. Specific code groups are inserted at specific positions in the frame to enable frame synchronization at the receiving end. Furthermore, to improve data randomness and prevent code synchronization loss, the data stream is scrambled. Scrambling uses a preset generator polynomial to ensure that 0s or 1s in the data sequence do not appear too frequently, thus avoiding system performance degradation.

[0076] Step S14: Data Encoding

[0077] Encoding is performed according to the laser communication protocol. After scrambling, the data stream is encoded according to a preset encoding method to improve communication reliability and efficiency. The encoded data is then ready for modulation.

[0078] Step S15: Signal Modulation

[0079] In the optical front-end module, the modulation driver amplifies the electrical signal and inputs it to the modulator for modulation to generate the corresponding optical signal. The optical signal is mapped according to the selected modulation method (such as QPSK, BPSK, etc.) and output to the spaceborne laser terminal for transmission.

[0080] S2, Multi-mode laser communication demodulation

[0081] The optical signal received by the test system is first processed by the optical front-end module; after being converted into an electrical signal, it undergoes analog-to-digital conversion by the ADC in the AD / DA module; the system then identifies the modulation format of the electrical signal according to a preset communication protocol and selects either coherent or incoherent processing based on the identification result; the coherent processing includes carrier acquisition, matched filtering, symbol synchronization, carrier tracking, and frame synchronization, followed by decoding, descrambling, and deframe processing; the specific demodulation process includes the following detailed steps:

[0082] Step S21: Optical signal reception and modulation format identification

[0083] The system first receives an optical signal from the onboard laser terminal and converts it into an electrical signal through an optical front-end module. After the signal is sampled by an ADC, the system identifies its modulation format and selects either coherent or incoherent processing based on the modulation method.

[0084] Step S22: Carrier acquisition and matched filtering

[0085] In the case of coherent demodulation, after the signal is sampled by the ADC, carrier acquisition calculation is first performed. The system determines the difference between the local oscillator frequency and the signal light frequency based on the acquisition result. The local oscillator frequency is adjusted by the control chip to complete carrier acquisition. After successful acquisition, the signal undergoes matched filtering to select the useful signal and suppress noise and interference.

[0086] Step S23: Symbol Synchronization

[0087] The matched-filtered signal enters the symbol synchronization loop. The system uses loop calculations to determine the optimal sampling point for the input data stream, thereby improving demodulation accuracy and synchronization performance. Symbol synchronization ensures that subsequent data can be processed in the correct timing.

[0088] Step S24: Carrier tracking and frequency offset compensation

[0089] After symbol synchronization, the system performs carrier tracking to further estimate and compensate for the slight frequency difference between the receiver and transmitter. Carrier tracking can correct the frequency offset in the received signal, ensuring that the demodulated signal is restored to symbol 0 or 1, and maintaining the stability of the communication system.

[0090] Step S25: Frame synchronization and decoding

[0091] Frame synchronization identifies the special code groups agreed upon in the protocol within the data frame, thereby determining the start and end of each data frame in the data stream. It then extracts the data from the data frame according to the agreed protocol, and finally descrambles and decodes the data to obtain valid data.

[0092] Step S26: Data storage and transmission

[0093] The valid data is transmitted to the CPU main control module for storage, statistics, and comparison of test data.

[0094] S3, Doppler frequency offset simulation

[0095] Step S31: The user software calculates the distance delay and Doppler frequency offset information to be simulated based on the relevant parameters of inter-satellite motion; the relevant parameters include the satellite's relative position, velocity vector, signal frequency, propagation delay, observation angle, timestamp, and orbital parameters (satellite orbit type (e.g., circular, elliptical) and its related orbital elements);

[0096] Step S32: The calculated analog information is transmitted to the optical front-end module as control information. The optical front-end module performs frequency offset compensation and signal attenuation control to ensure that the signal adjustment meets expectations.

[0097] Step S33: The simulated laser signal is split into beams by a beam splitter for real-time monitoring of the optical signal status.

[0098] Throughout the testing process, the CPU main control module is responsible for managing and scheduling various functional modules to ensure that each part of the system works according to the predetermined process.

[0099] The CPU main control module collects and processes test data in real time, and communicates with other modules at high speed through the PCIe bus to ensure seamless data transmission.

[0100] The CPU main control module can also communicate with the satellite platform via a high-speed interface, supporting remote data monitoring and processing, ensuring the flexibility and efficiency of the entire testing system.

[0101] To address the testing needs of various spaceborne laser terminals, this invention presents a laser communication ground simulation device with a CPCI architecture. Through modular design, it supports laser communication tasks at multiple rates and with various systems, as well as interface link testing tasks. The device encompasses multi-rate, universal high-speed laser communication technologies, including modulation and demodulation techniques for multi-rate laser communication, achieving comprehensive coverage of testing requirements at different communication rates and meeting the testing requirements of various spaceborne laser terminals.

[0102] This invention provides a ground simulation device for spaceborne laser communication terminals applicable to various data rate systems through modular design, PCIe bus data interaction, flexible clock configuration, and Doppler frequency offset control. Its design significantly improves the device's versatility and flexibility, meeting the testing requirements of different laser terminal models, reducing equipment development and maintenance costs, and has broad application prospects.

[0103] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A spaceborne laser terminal simulation and testing device for multiple rate systems, characterized in that, include: The CPU main control module is responsible for the overall system control and the collection and processing of test data; The clock module is used to provide multiple clock signal outputs to ensure system synchronization at different speeds; The digital interface module is used for low-speed data communication, supports multiple interfaces, and performs data processing through an FPGA chip. The digital processing module is responsible for high-speed data processing, signal modulation and demodulation, and digital signal processing is implemented through an FPGA chip. The optical front-end module is used for transmitting and receiving laser signals, and simulates Doppler frequency shift and signal attenuation; The clock module is equipped with a DIP switch; the DIP switch is used to switch between internal and external clocks; when the DIP switch is set to 0, it is the internal clock; when the DIP switch is set to 1, it is the external clock; wherein, the internal clock is a 10MHz high-stability clock, and the external clock is a clock source of arbitrary frequency. The optical front-end module includes a bias controller, a modulator, an optical attenuator, a beam splitter, an optical amplifier, and an optical filter; The beam splitter feeds the split signal light to the bias controller to control the modulator's operation; The optical attenuator is used to prevent damage to the spaceborne laser terminal caused by excessive optical power between the system and the spaceborne laser terminal. The optical amplifier is used to make the input power of the back-end demodulation reach a set threshold. The optical filter is used to filter out noise and equalize the gain of the amplified signal light. The CPU main control module includes a CPCI motherboard; the CPCI motherboard is equipped with an SSD solid-state drive and DDR3 memory; the CPCI motherboard is also equipped with external interfaces; the external interfaces include a Gigabit Ethernet interface and a USB 2.0 / 3.0 interface; The digital processing module includes two FPGA processing modules, an optical signal coherent receiving module, and an AD / DA module; the two FPGA modules are FPGA_0 module and FPGA_1 module, respectively. The FPGA_0 module uses an internal FPGA hard core to implement communication between the PCIE interface and the CPU main control module for transmitting data core control information; the FPGA_0 module completes the timing control of the high-speed interface with the satellite platform through a high-speed interface chip; the FPGA_0 module is connected to the FPGA_1 module through an SRIO interface to realize dynamic loading of the program of the FPGA_1 module. The FPGA_1 module is used to perform complex signal processing functions, including signal modulation, demodulation, and encoding / decoding. The AD / DA module is used for analog-to-digital / digital-to-analog conversion of signal modulation and demodulation; The optical signal coherent receiving module is electrically connected to the AD / DA module.

2. The spaceborne laser terminal simulation and testing equipment for multiple rate systems according to claim 1, characterized in that, The CPU main control module also includes a keyboard, mouse, and display device to provide a UI interface; the UI interface is used to enable users to perform human-computer interaction and complete corresponding operations.

3. The spaceborne laser terminal simulation and testing equipment for multiple rate systems according to claim 1, characterized in that, The digital interface module communicates with the CPU main control module via an Ethernet port; the digital interface module includes an FPGA management module, a 422 communication interface module, an LVDS interface module, an Ethernet control module, and a Flash module; the 422 communication interface module, LVDS interface module, Ethernet control module, and Flash module are all communicatively connected to the FPGA management module; the digital interface module manages the 1PPS synchronization signal and realizes telemetry and remote control communication through the FPGA management module.

4. A method for simulating and testing a spaceborne laser terminal for multiple rate systems, applied to the spaceborne laser terminal simulation and testing equipment for multiple rate systems as described in any one of claims 1-3, characterized in that, The simulation test method for spaceborne laser terminals with multiple rate systems includes the following steps: S1, Multi-rate laser communication modulation Test data is transmitted from the CPU main control module to the digital processing module via the PCIe bus; the digital processing module resamples the data according to the preset communication rate and adjusts the data rate through interpolation and decimation techniques. The data stream is framed and scrambled at a set rate. The encoded data is converted from electrical signal to optical signal by the optical front-end module and then transmitted to the onboard laser terminal. S2, Multi-mode laser communication demodulation The optical signal received by the test system is first processed by the optical front-end module; after the optical signal is converted into an electrical signal, it is converted into an analog-to-digital signal by the ADC in the AD / DA module; the system then identifies the modulation format of the electrical signal according to the preset communication protocol, and selects coherent or incoherent processing mode based on the identification result; The coherent processing includes carrier acquisition, matched filtering, symbol synchronization, carrier tracking and frame synchronization, followed by decoding, descrambling and deframe processing. S3, Doppler frequency offset simulation The user software calculates the distance delay and Doppler frequency offset information to be simulated based on the relevant parameters of inter-satellite motion; the relevant parameters include the satellite's relative position, velocity vector, signal frequency, propagation delay, observation angle, timestamp, and orbital parameters; The calculated analog information is transmitted to the optical front-end module as control information. The optical front-end module performs frequency offset compensation and signal attenuation control to ensure that the signal adjustment meets expectations. The simulated laser signal is split into beams by a beam splitter for real-time monitoring of the optical signal status.

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