A V-band microwave satellite-ground time difference measurement simulation system

Abstract

The application discloses a V-band microwave satellite-ground time difference measurement simulation system and method, which comprises a ground terminal simulation subsystem and a space terminal simulation subsystem, the ground terminal simulation subsystem and the space terminal simulation simulation subsystem share a clock unit as a frequency reference; the ground terminal simulation subsystem and the space terminal simulation subsystem both comprise a comprehensive processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit and a frequency comprehensive unit, and are used for ground simulation verification of high-precision microwave time frequency transmission in satellite-ground, satellite-satellite and ground-moon scenes; the ground terminal simulation subsystem and the space terminal simulation subsystem are both used for signal generation, emission, reception processing, time difference measurement, time delay simulation and error correction of a device layer and a space transmission layer, and can accurately calculate the relative clock difference between the space terminal and the ground terminal, so that satellite-ground time comparison is realized.

Description

Technical Field

[0001] This application relates to the field of satellite communication technology, and in particular to a V-band microwave satellite-to-ground time difference measurement simulation system and method. Background Technology

[0002] Building an integrated space-ground time and frequency system is an important development direction. Currently, my country is promoting the construction of a national time service system that integrates space, ground, and three-dimensional communication.

[0003] With the deployment and implementation of major projects such as my country's manned spaceflight, lunar exploration, and Mars exploration, the demand for space time and frequency technology is increasing. Cutting-edge research in technologies such as space / deep space time and frequency standards and lunar standard time relies heavily on tracing and comparing with Earth's standard time, and satellite-to-ground time difference measurement is the core of this tracing and comparison. Ultra-high precision satellite-to-ground microwave time difference measurement links can support precise measurements of relevant physical quantities and constants in scientific research, and provide high-precision verification of relativity and other developing physical theories; in navigation and positioning, they can improve the system service accuracy of the BeiDou Navigation Satellite System; and in future communications, they are a fundamental technology for ensuring the synchronization of high-speed communication networks and improving the efficiency and reliability of data transmission.

[0004] Regarding space-to-ground time difference measurement links, picosecond-level time difference comparison results have been achieved under complex environments. However, for the broader and more complex space environment of the future, further exploration of time difference comparison links between Earth satellites and the ground in different orbits, and between lunar satellites and the ground, is needed. Currently, there is a lack of a microwave space-to-ground time difference measurement simulation system that can be rapidly simulated and verified on the ground. A simulation system serves as an effective means of verifying high-precision microwave time and frequency transfer in multiple scenarios, including space-to-ground, inter-satellite, and Earth-Moon scenarios, and supports the technical verification and construction of the national space time and frequency system. It can also serve as a technical verification platform for exploring next-generation microwave time and frequency transfer technologies. Summary of the Invention

[0005] The main purpose of this application is to provide a V-band microwave satellite-to-ground time difference measurement simulation system and method, which aims to solve the technical problems of ultra-high precision microwave time difference measurement link and establish a ground simulation system.

[0006] To achieve the above objectives, this application provides a V-band microwave satellite-to-ground time difference measurement simulation system, comprising: The ground-based simulation subsystem and the space-based simulation subsystem share a clock unit as a frequency reference. Both the ground-side simulation subsystem and the space-side simulation subsystem include an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit, and a frequency integration unit, which are used for ground simulation verification of high-precision microwave time and frequency transmission in satellite-to-ground, inter-satellite, and Earth-Moon scenarios. Both the ground-side simulation subsystem and the space-side simulation subsystem are used for signal generation, transmission, reception, and processing, as well as time delay simulation at the equipment layer and the space transmission layer; the ground-side simulation subsystem is also used for time difference measurement and error correction based on the received bidirectional measurement data; Among them, equipment layer errors include clock error, baseband measurement error, RF channel delay error, frequency synthesis error, and antenna phase center offset error; Space transport layer delays and errors include spatial distance delays, atmospheric delays, delays due to general and special relativistic effects, and multipath effect errors.

[0007] Optionally, the units in the control system include an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit, a clock unit, and a frequency synthesis unit. The integrated processing unit includes: A high-performance computer platform with supporting integrated processing software is used for network-based remote control and display simulation systems, human-computer interaction and data storage, as well as monitoring and controlling the workflow and operating conditions in the control system, and coordinating the work of various units in the control system for telemetry analysis and business data storage and analysis.

[0008] Optionally, the space environment simulation unit includes: A high-performance computer platform with a matching digital simulation model of the space environment; The space environment digital simulation model includes: Spatiotemporal system model, satellite orbit model, user trajectory model, observation data model, space environment model, high dynamic model, and ranging message model; The high-performance computer platform is used to convert the parameters of the digital simulation model of the space environment into the carrier frequency, phase and pseudocode rate, and phase modulation parameters of the signal, and then send them to the baseband signal processing unit.

[0009] Optionally, it also includes: A constant temperature microwave anechoic chamber environment, including a precision temperature-controlled air conditioner and a microwave anechoic chamber; Among them, precision temperature control air conditioners are used to control time delay changes caused by temperature changes; Microwave anechoic chambers are used to reduce signal reflection by absorbing microwaves, thereby eliminating the effects of temperature variations and multipath effects on measurements of the ground-based and space-based analog subsystems.

[0010] Optionally, the baseband signal processing unit includes: High-performance processor, multi-channel ADC and multi-channel DAC; Among them, the high-performance processor is used to complete baseband signal generation, intermediate frequency transmission and reception, and baseband signal reception processing; Multi-channel ADCs and multi-channel DACs have external reference mode and direct clock mode, which can be used to directly drive signals with different baseband symbol rates for analog and reception via an external clock.

[0011] Optionally, the V-band radio frequency unit includes: Up-converter module and down-converter module; The downconversion module is used to complete the receiving filtering, amplification and downconversion processing, while the upconversion module is used to complete the transmitting baseband signal filtering, amplification and upconversion processing.

[0012] Optionally, the frequency synthesis unit is a high-stability microwave frequency source module, used to provide three frequency reference modes: internal reference mode, external reference mode, and external local oscillator mode. The internal reference mode uses an internally integrated high-stability crystal oscillator, the external reference mode uses a 10MHz frequency source provided by the clock unit, and the external local oscillator mode receives a low-phase-noise optically generated microwave frequency source signal from the clock unit.

[0013] Optionally, the clock unit includes at least one of a rubidium clock, a cesium clock, a hydrogen clock, and a photogenerated microwave frequency source, used to provide an external clock reference for the frequency synthesis unit.

[0014] Optionally, the clock unit can be a clock from the same source or a clock from different sources and independent. The same source mode is used to evaluate the additional noise of the simulation link, while the different source mode is used to evaluate the clock difference between the two ends of the ground-end simulation subsystem and the space-end simulation subsystem.

[0015] Furthermore, to achieve the above objectives, this application also provides a V-band microwave satellite-to-ground time difference measurement simulation method, comprising: In the ground-side simulation subsystem, configuration files are input or loaded through the space environment simulation software interface of the space environment simulation unit to set space transmission environment parameters and generate scene files. The scene files are transmitted to the baseband signal processing unit of the ground-side simulation subsystem via a network protocol and a communication interface. The scene files are then processed based on simulation algorithms to obtain a baseband signal superimposed with time delay errors and space transmission layer errors. The simulation algorithms include at least one of clock difference simulation algorithm, baseband error algorithm, radio frequency channel time delay algorithm, relativistic time delay algorithm, and atmospheric time delay algorithm. The superimposed time delay error and space transmission layer error are sent to the radio frequency unit. After up-conversion by the radio frequency unit, the power is adjusted by the power control unit to obtain the first signal. The ground-end analog subsystem sends the first signal to the space-end analog subsystem. After receiving the first signal, the signal receiving and processing module of the space-end analog subsystem demodulates the first signal and extracts the first measurement data by the baseband signal processing unit, and transmits the first measurement data to the ground-end analog subsystem via the microwave link. In the space-end simulation subsystem, a second signal is sent to the ground-end simulation subsystem in a symmetrical manner with the ground-end simulation subsystem. The ground-end simulation subsystem receives and processes the second signal and extracts the second measurement data. Based on the obtained first and second measurement data, the correction algorithm is called and the equipment layer error and time delay error are deducted according to the space transmission environment parameters in the scenario file to obtain the simulation results of V-band microwave satellite-to-ground time difference measurement.

[0016] This application proposes a V-band microwave satellite-to-ground time difference measurement simulation system and method. The system includes a ground-end simulation subsystem and a space-end simulation subsystem, which share a clock unit as a frequency reference. Both the ground-end and space-end simulation subsystems include a comprehensive processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit, and a frequency integration unit, used for ground simulation verification of high-precision microwave time and frequency transfer in satellite-to-ground, inter-satellite, and Earth-Moon scenarios. The simulation subsystems are used for signal generation, transmission, reception, and processing, as well as time delay simulation at the equipment layer and space transmission layer. The ground-side simulation subsystem is also used for time difference measurement and error correction based on the received bidirectional measurement data. Among them, the equipment layer errors include clock error, baseband measurement error, radio frequency channel delay error, frequency synthesis error, and antenna phase center offset error. The space transmission layer delay and errors include spatial distance delay, atmospheric delay, generalized and special relativistic effect delay, and multipath effect error. It can accurately calculate the relative clock difference between the space end and the ground end, thereby realizing satellite-to-ground time comparison. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the workflow of an embodiment of the V-band microwave satellite-to-ground time difference measurement simulation system of this application; Figure 2 A simplified diagram of the simulation system equipment provided in an embodiment of the microwave satellite-to-ground time difference measurement simulation system of this application; Figure 3 This is a schematic diagram of a simulation system provided for an embodiment of the microwave satellite-to-ground time difference measurement simulation system of this application; Figure 4 This is a schematic diagram of a V-band satellite-to-ground microwave time difference measurement simulation system according to an embodiment of the microwave satellite-to-ground time difference measurement simulation system of this application; The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0019] It should be noted that the most effective way to improve carrier measurement accuracy is to increase the carrier frequency. The measurement method using the V-band in this invention is based on this consideration, aiming to break through the existing picosecond-level measurement error bottleneck. However, the satellite-to-ground time difference measurement simulation system proposed in this invention is also applicable to other frequency bands such as K and Ka. Reference Figure 1 The first embodiment of this application provides a V-band microwave satellite-to-ground time difference measurement simulation system, which may include: The ground-based simulation subsystem and the space-based simulation subsystem share a clock unit as a frequency reference. In one embodiment of this application, the clock unit includes at least one of a rubidium clock, a cesium clock, a hydrogen clock, and a photogenerated microwave frequency source, used to provide an external clock reference for the frequency synthesis unit. The clock unit can be a clock from the same source or a non-same-source, independent clock. The same-source mode is used to evaluate the additional noise of the simulation link, while the non-same-source mode is used to evaluate the clock difference between the ground-side simulation subsystem and the space-side simulation subsystem.

[0020] Specifically, the clock unit, as the core of the frequency reference of the entire analog system, needs to be selected based on the actual measurement accuracy requirements. Specifically, rubidium clocks have the characteristics of good short-term stability and moderate size, making them suitable for conventional accuracy scenarios; cesium clocks and hydrogen clocks have higher long-term stability and can meet the requirements of picosecond-level ultra-high precision time difference measurement; and optically generated microwave frequency sources can provide low phase noise frequency signals, making them suitable for noise-sensitive measurement scenarios.

[0021] The ground-side simulation subsystem consists of an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, a radio frequency unit, an antenna unit, a power control unit, a frequency synthesis unit, and a clock unit. The clock unit serves as a shared frequency reference between the ground-side simulation subsystem and the space-side subsystem, enabling the verification of the time-frequency measurement comparison performance of the satellite-to-ground microwave link. The space environment simulation software has a communication interface with the baseband signal processing board. The software configures the current simulated space transmission environment, and the signal processing board generates the corresponding wireless signal based on the configured scenario file.

[0022] The space-end simulation subsystem consists of an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, an RF antenna unit, a frequency synthesis unit, and a power control unit. The space environment simulation software has a communication interface with the baseband signal processing board. The space environment simulation software configures the current simulated space transmission environment, and the signal processing board generates the corresponding wireless signal based on the scenario file generated by the configuration.

[0023] The constant-temperature microwave anechoic chamber environment mainly consists of a precision temperature-controlled air conditioner and a microwave anechoic chamber, forming a relatively independent ultra-stable time-frequency performance testing environment. This reduces interference factors such as electromagnetic and temperature interference, thereby improving testing effectiveness and efficiency. Precision temperature control effectively manages time delay changes caused by temperature variations, eliminating the influence of temperature variations and allowing for more accurate evaluation of measurement performance. Anechoic chamber absorption reduces signal reflection, eliminates the influence of multipath propagation on measurements, and ensures cleaner signal reception, achieving the goal of accurately evaluating equipment-level measurement performance.

[0024] Clearly, by employing a high-precision clock unit and achieving dual-end sharing, it is possible to ensure that the frequency references of the ground-side and space-side analog subsystems are from the same source, thereby reducing the measurement errors introduced by the frequency reference difference from the source. This lays the foundation for subsequent high-precision time difference calculation, enabling a more accurate assessment of the noise level of the measurement link itself.

[0025] Both the ground-side simulation subsystem and the space-side simulation subsystem include an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit, and a frequency integration unit, which are used for ground simulation verification of high-precision microwave time and frequency transmission in satellite-to-ground, inter-satellite, and Earth-Moon scenarios. In one embodiment of this application, the units in the control system include an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit, a clock unit, and a frequency integration unit. The integrated processing unit includes a high-performance computer platform with supporting integrated processing software, used for network-based remote control and display simulation system, human-computer interaction and data storage, as well as monitoring the workflow and operating conditions in the control system. The units in the control system work together to perform telemetry analysis and business data storage and analysis.

[0026] The integrated processing unit consists of a high-performance computer platform and supporting integrated processing software, which can remotely control and display the equipment of the simulation system via a network. As the interactive display and control platform for the simulation system, it provides a human-machine interface and data storage; monitors the system's workflow and operating conditions; controls the collaborative work of various subsystems within the test system; and performs telemetry analysis and business data storage and analysis.

[0027] Clearly, the design of the integrated processing unit enables centralized control of the system and improves operational convenience.

[0028] In one embodiment of this application, the space environment simulation unit includes a high-performance computer platform with a matching space environment digital simulation model; wherein, the space environment digital simulation model includes a spatiotemporal system model, a satellite orbit model, a user trajectory model, an observation data model, a space environment model, a high dynamic model, and a ranging message model; the high-performance computer platform is used to convert the parameters of the space environment digital simulation model into the carrier frequency, phase and pseudocode rate, and phase modulation parameters of the signal and send them to the baseband signal processing unit.

[0029] Specifically, the space environment simulation unit consists of a high-performance computer platform and a supporting digital simulation model of the space environment, including a spatiotemporal system model, a satellite orbit model, a user trajectory model, an observation data model, a space environment model, a high dynamic model, a ranging message model, etc. Ultimately, the model parameters are converted into the carrier frequency, phase and pseudocode rate of the signal, and phase modulation parameters, which are then sent to the baseband signal processing to generate the signal after being simulated and modulated by the space transmission environment.

[0030] For example, the spatiotemporal system model is used to define the time and space coordinate system of the measurement scenario, providing a benchmark for subsequent orbit calculation and time delay simulation; the satellite orbit model can simulate the motion state of various orbit types such as Earth satellites and lunar satellites according to different mission requirements; the user trajectory model can simulate the movement trajectory of the ground receiver and adapt to dynamic measurement scenarios; and the space environment model can restore the atmospheric environment characteristics such as the ionosphere and troposphere.

[0031] In addition, the space environment simulation unit transforms abstract environmental parameters into signal modulation parameters that can be recognized by the baseband signal processing unit, providing an input basis that fits the actual scenario for subsequent signal generation.

[0032] In one embodiment of this application, the baseband signal processing unit includes a high-performance processor, a multi-channel ADC, and a multi-channel DAC; wherein, the high-performance processor is used to perform baseband signal generation, intermediate frequency transmission and reception, and baseband signal reception processing; the multi-channel ADC and multi-channel DAC have external reference mode and direct clock mode, and are used to directly drive the analog and reception of signals with different baseband symbol rates through an external clock.

[0033] Optionally, the baseband signal processing unit's main task is to accurately generate intermediate frequency (IF) analog signals based on the satellite-to-ground link model generated by the space environment simulation unit. Considering the Doppler effect, the carrier phase and pseudocode phase remain correlated, and signal power and phase are controllable. It includes a high-performance processing FPGA, DSP, multi-channel ADC, and multi-channel DAC. The FPGA and DSP perform baseband signal generation, IF transmission and reception, and baseband signal reception processing. The FPGA processor interacts with the integrated processing unit and space environment simulation unit via a network to exchange measurement data and control commands. Both the ADC and DAC employ a flexible direct clock design, supporting external reference mode and direct clock mode. The external clock directly drives the operation. By providing external reference clocks of different frequencies, signal simulation and reception processing at various baseband symbol rates can be achieved, and the impact of phase noise and thermal noise from the digital board's frequency synthesizer unit on measurement accuracy can be minimized.

[0034] In one possible implementation, the baseband signal processing unit effectively reduces the impact of limited clock performance on measurement accuracy by using an external clock drive.

[0035] In one embodiment of this application, the V-band radio frequency unit includes an up-conversion module and a down-conversion module; wherein, the down-conversion module is used to perform receiving filtering, amplification and down-conversion processing, and the up-conversion module is used to perform transmitting baseband signal filtering, amplification and up-conversion processing.

[0036] Specifically, in the transmit link, the upconversion module converts the intermediate frequency signal output by the baseband signal processing unit into a V-band radio frequency signal. During this process, the filtering module can filter out noise interference, and the amplification module increases the signal power to a level suitable for transmission. In the receive link, the downconversion module receives the V-band signal from the antenna unit, and converts it into an intermediate frequency signal after filtering and amplification, so that the baseband signal processing unit can perform subsequent processing.

[0037] Clearly, the upconversion and downconversion modules of the V-band RF unit have a clear division of labor. Through filtering and amplification, they ensure the purity and strength of the signal transmitted in the V-band, providing reliable RF signal support for the simulation of the satellite-to-ground microwave link.

[0038] In one embodiment of this application, the frequency synthesis unit is a high-stability microwave frequency source module, which is used to provide three frequency reference modes: internal reference mode, external reference mode, and external local oscillator mode. The internal reference mode uses an internally integrated high-stability crystal oscillator, the external reference mode uses a 10MHz frequency source provided by the clock unit, and the external local oscillator mode receives a low-phase-noise optically generated microwave frequency source signal from the clock unit.

[0039] The frequency synthesis unit is a high-stability microwave frequency source module that provides a local oscillator for the up-conversion and down-conversion channels and an ADC / DAC reference clock for baseband processing. The frequency source module has three frequency reference modes: internal reference, external reference, and external local oscillator. In internal reference mode, the high-stability crystal oscillator integrated within the frequency source is used as the reference. In external reference mode, a more stable frequency source (10MHz) provided by the clock unit is used, typically a cesium atomic clock or a hydrogen atomic clock. When operating with an externally input RF local oscillator frequency signal, such as a low-phase-noise optically generated microwave frequency source from the clock unit, a frequency signal with even better phase noise levels can be provided.

[0040] It should be noted that the three frequency reference modes can be flexibly switched according to the actual application scenario. The internal reference mode does not require an external clock input, is easy to use, and is suitable for preliminary testing or scenarios with low accuracy requirements; the external reference mode connects to the 10MHz high-stability frequency source of the clock unit, which can improve frequency stability and adapt to medium-precision measurement needs; the external local oscillator mode receives a low-phase-noise optically generated microwave frequency source signal, which can further reduce phase noise and meet the requirements of ultra-high precision time difference measurement.

[0041] Clearly, the multi-mode design of the frequency synthesis unit enables the system to adapt to different accuracy requirements. At the same time, the selection of a high-stability microwave frequency source provides a stable clock reference for the RF unit and the baseband signal processing unit, ensuring the accuracy of the signal frequency.

[0042] Both the ground-based simulation subsystem and the space-based simulation subsystem are used for signal generation, transmission, reception, and processing, as well as time delay simulation at the equipment layer and the space transmission layer. The ground-based simulation subsystem is also used for time difference measurement and error correction based on the received bidirectional measurement data. Among them, the equipment layer errors include clock bias, baseband measurement error, radio frequency channel delay error, frequency synthesis error, and antenna phase center offset error. The space transmission layer delays and errors include spatial distance delay, atmospheric delay, delay due to general and special relativistic effects, and multipath effect error.

[0043] Among them, clock error refers to the time difference between the ground end and the space end clock, which is the core error source affecting time difference measurement; baseband measurement error originates from noise interference and algorithm errors in the baseband signal processing process, such as the accuracy deviation in the signal modulation and demodulation process; RF channel delay error is the fixed delay and dynamic delay generated by the RF signal in the transmission channel; frequency synthesis error is the deviation between the output frequency of the frequency synthesis unit and the standard frequency; and antenna phase center offset error is the measurement error caused by the offset between the actual phase center and the theoretical phase center of the antenna.

[0044] It should be noted that spatial distance delay is the time delay caused by the distance of a signal propagating in space, and is directly related to the distance between the two ends; atmospheric delay is the time delay caused by changes in atmospheric refractive index when the signal passes through the ionosphere and troposphere, and is affected by factors such as weather and altitude; general and special relativistic effect delay is the time delay caused by the time dilation effect due to the high-speed motion of the satellite and changes in the gravitational field; multipath effect error is the measurement error caused by the superposition of signals after propagating through different paths.

[0045] like Figure 2 As shown, the two space simulation systems and the ground-based simulation subsystem adopt a symmetrical design, with each baseband processing module integrating one intermediate frequency (IF) transmission processing module and one IF reception processing module. Optionally, when the system supports multi-frequency links, the IF and RF modules are multi-channel transceiver modules.

[0046] The intermediate frequency (IF) transmission processing module contains two or more independent channels. Each channel independently completes information encoding into frames, channel coding, spread spectrum, modulation, shaping filtering, digital up-conversion processing, and finally generates the transmit IF signal through DAC output. At the same time, the IF transmission processing module receives phase and power control commands from the environmental simulation unit.

[0047] The intermediate frequency (IF) receiver processing module contains two or more independent processing channels. Each channel independently completes ADC sampling, digital down-conversion processing, acquisition and tracking, demodulation, channel decoding, and framing and packet uploading of the down-converted IF received signal. During the acquisition and tracking process, pseudorange and carrier phase measurements are extracted. The extracted carrier measurement measurements are further used for precise carrier ranging, frequency comparison, and measurement functions. Clock error and ranging values ​​can be calculated based on bidirectional microwave measurements.

[0048] refer to Figure 3 As shown, the overall system workflow can be divided into four stages: signal generation, transmission simulation, reception processing, and error correction. The specific implementation steps are as follows: (1) Environment configuration stage: The user inputs or loads a configuration file through the space environment simulation software interface of the space environment simulation unit, sets the space transmission environment parameters for the current simulation, and generates a scene file. This file is transmitted to the baseband signal processing unit through the communication interface.

[0049] (2) Signal generation and transmission stage: In the baseband signal processing unit, the signal processing algorithm calculates the superimposed time delay error based on the scene file; the baseband measurement signal is modulated, and after the signal is up-converted by the radio frequency unit, the power is adjusted by the power control unit to simulate space loss. The ground terminal system signal is sent to the space terminal system, and the space terminal system signal is sent to the ground terminal system to simulate the satellite-to-ground wireless link.

[0050] (3) Transmission simulation stage: During signal transmission, space transmission layer errors are simulated in real time. For example, the baseband signal processing unit embeds a multipath effect model and a relativistic time delay module during the signal generation stage to simulate errors caused by dynamic changes in satellite orbit.

[0051] (4) Reception and Processing Stage: After the signal receiving and processing modules of the space-end simulation subsystem and the ground-end simulation subsystem receive the signal, the baseband signal processing unit demodulates the signal and extracts the raw measurement data, while recording the equipment layer error at the receiving end. The data is transmitted back through the integrated processing unit, realizing the interaction of bidirectional measurement data under the microwave link based on the integrated measurement and communication signal system.

[0052] (5) Time difference measurement and error correction stage: The integrated processing unit at the ground end processes the two-way time difference data, calculates the initial clock difference value, and calls the correction algorithm to deduct the equipment layer and space transmission layer errors according to the parameters in the scenario file. Finally, the time difference measurement results are output to the display or storage device for clock difference analysis and system performance evaluation.

[0053] In this embodiment, the design of its key components is described below.

[0054] Error simulation module: At the device layer, the baseband signal processing unit embeds a clock bias simulation module, a baseband error module, and a radio frequency channel delay module. In the space transport layer simulation, the software calls upon atmospheric model libraries, relativistic models, etc.

[0055] Hardware implementation: In the preferred embodiment, the baseband signal processing board is a commercial FPGA or DSP board, the radio frequency unit uses the V-band, and the clock unit uses a commercial atomic clock.

[0056] Communication Protocol: The space environment simulation software and the baseband unit use a network protocol to transmit scenario files. Through the above implementation methods, the system achieves full-link simulation of the satellite-to-ground microwave link with picosecond-level accuracy, effectively solving the problem of ultra-high precision time and frequency transmission. Those skilled in the art can adjust parameters and hardware selection according to specific application scenarios to meet the needs of different satellite-to-ground scenarios, different link budgets, and different measurement accuracies.

[0057] Based on the above system embodiments, this application also provides a V-band microwave satellite-to-ground time difference measurement simulation method, which is applied to the above V-band microwave satellite-to-ground time difference measurement simulation system. The method mainly includes three core steps: signal transmission and reception, error processing, and clock difference calculation.

[0058] S101. In the ground-side simulation subsystem, the space environment simulation software interface of the space environment simulation unit is used to input or load configuration files, set space transmission environment parameters and generate scene files. The scene files are transmitted to the baseband signal processing unit of the ground-side simulation subsystem via the communication interface through the network protocol. The scene files are then processed based on simulation algorithms to obtain a baseband signal superimposed with time delay error and space transmission layer error. The simulation algorithms include clock difference simulation algorithm, baseband error algorithm, radio frequency channel time delay algorithm, relativistic time delay algorithm and atmospheric time delay algorithm. S102. The superimposed time delay error and space transmission layer error are sent to the radio frequency unit. After up-conversion by the radio frequency unit, the power is adjusted by the power control unit to obtain the first signal. The ground-end simulation subsystem sends the first signal to the space-end simulation subsystem. After receiving the first signal, the signal receiving and processing module of the space-end simulation subsystem demodulates the first signal and extracts the bidirectional time difference data of each. At the same time, it records the equipment layer error of the receiving end, calculates the initial value of the clock difference, calls the correction algorithm, and deducts the equipment layer error and time delay error according to the space transmission environment parameters in the scenario file to obtain the first measurement data. The first measurement data is then transmitted to the ground-end simulation subsystem via the microwave link. S103. In the space-end simulation subsystem, a second signal is sent to the ground-end simulation subsystem in a manner symmetrical with that of the ground-end simulation subsystem. The ground-end simulation subsystem extracts the second measurement data. Based on the obtained first and second measurement data, a correction algorithm is called and the equipment layer error and time delay error are deducted according to the space transmission environment parameters in the scenario file to obtain the simulation results of V-band microwave satellite-to-ground time difference measurement.

[0059] The correction algorithm, based on the principle of bidirectional time comparison, is used to extract and eliminate various simulation errors from the original measurement data, thereby accurately reproducing the simulated "relative clock difference between the space end and the ground end." Specifically, by receiving the original first and second measurement data obtained from the interaction between the ground end and the space end, combining the measured equipment layer error, subtracting the space transmission layer error based on the preset scenario of the space environment simulation unit, and utilizing the common-mode error suppression characteristics inherent in the bidirectional comparison structure, the relative clock difference between the space end and the ground end is finally accurately calculated from the original measurement data coupled with various errors, thus outputting the final high-fidelity simulation result of V-band microwave satellite-to-ground time difference measurement, completing the verification closed loop from error simulation to error correction.

[0060] refer to Figure 4 Specifically, the principle of V-band microwave satellite-to-ground time difference measurement simulation is as follows: Microwave time and frequency measurement equipment at both the space and ground ends achieve signal transmission and reception functions through radiating antennas, thereby constructing a two-way ranging system between space and ground stations. During the establishment period of the space-to-ground link, the ground-end simulation equipment and the space-end simulation equipment perform two-way ranging. By performing system-level error processing (including orbit determination accuracy, motion delay error, relativistic delay error, ionospheric delay error, and tropospheric delay error) on the raw two-way carrier measurement data of the space-to-ground simulated link, the relative clock difference between the space end and the ground end is accurately calculated, thereby achieving space-to-ground time comparison.

[0061] The space station and the ground station continuously conduct bidirectional measurements by exchanging ranging signals. Each time a set of bidirectional ranging values ​​is extracted, a clock error calculation is completed. Assume the extracted downlink ranging signal is from the space station... Sending messages constantly, at the ground end Received continuously; uplink ranging signals are received by the ground station. Sending in real time, on the space end Real-time reception, the corresponding dual unidirectional ranging process is as follows: Figure 4 As shown.

[0062] The one-way pseudorange measurement between the space and ground ends is calculated from the local time difference between transmission and reception, including clock difference information between the space and ground ends at the signal transmission and reception times. The propagation of the ranging signal is affected by hardware delays in the transceiver equipment and spatial propagation delays. Hardware delays cannot be canceled out by bidirectional measurements and require precise calibration for compensation. Spatial signal propagation delays include not only the spatial distance delay between the space end and the ground station, but also additional delays introduced by atmospheric refraction and phase center shift along the signal propagation path, as well as equivalent delays due to relativistic effects and the Sagnac effect. Therefore, within the Earth-Fixed Coordinate System (ECEF) framework, the measurement equations for a single two-way one-way measurement between the space and ground ends can be established:

[0063] Where c is the speed of light in a vacuum; and These are the position vectors of the space end and the ground end in ECEF, respectively; and These are the clock differences at the space end and the ground end, respectively; and The hardware transmission delay for the signal transmission and reception channels; This is the equivalent time delay due to relativistic effects; This is the equivalent time delay for the Sagnac effect; This is the equivalent time delay due to multipath effects; This is the equivalent time delay due to the phase center offset; This is ranging noise.

[0064] In time comparison between the space station and the ground station, the atomic clock time at the ground station is used as the reference time, and the clock difference at the ground station can be considered as... Furthermore, under ECEF, the ground position coordinates are constant, therefore the above measurement equation can be simplified to:

[0065] When the time of the ranging signals transmitted and received at the space end is inconsistent, the two unidirectional ranging signals contain the space end clock difference at different times, which needs to be normalized to the same time through time stamping, that is:

[0066] in, This is the clock bias correction at the space station. By subtracting the two-way ranging equations, the two-way time synchronization equations between the space station and the ground station can be obtained, and the clock bias at the space station can be calculated.

[0067] Among them, the two-way spatial distance is calculated by precise orbit determination at the space end, the clock error correction is calculated by predicted clock error at the space end, the hardware transmission delay is calibrated periodically, atmospheric delay, relativistic effects, Sagnac effects, and phase center offset can be calculated based on mathematical models, and multipath effects are suppressed through system design and anti-multipath antenna design.

[0068] By establishing measurement equations that incorporate multiple factors such as space propagation delay, hardware delay, and relativistic effects, a simplified model based on ground-based atomic clock time is derived. A timescale reduction method is used to unify clock error observation times, and error separation is achieved by combining orbital parameters, atmospheric parameters, and measurement data. Statistical analysis of the observation results provides an assessment of the stability of the clock error.

[0069] Specifically, when the space end and the ground end use the same clock reference, it can be used to assess the additional noise level of the time difference measurement system.

[0070] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A V-band microwave satellite-to-ground time difference measurement simulation system, characterized in that, Ground-based simulation verification of high-precision microwave time-frequency transfer in satellite-to-ground, inter-satellite, or Earth-Moon scenarios includes: The ground-based simulation subsystem and the space-based simulation subsystem share a clock unit as a frequency reference. Both the ground-based simulation subsystem and the space-based simulation subsystem include an integrated processing unit, a space environment simulation unit, a baseband signal processing unit, a V-band radio frequency unit, an antenna unit, a power control unit, and a frequency synthesis unit. The space environment simulation unit and the integrated processing unit are communicatively connected to the baseband signal processing unit. The baseband signal processing unit is connected to the V-band radio frequency unit, the V-band radio frequency unit is connected to the antenna unit, the power control unit is connected to the V-band radio frequency unit, and the frequency synthesis unit is connected to both the baseband signal processing unit and the V-band radio frequency unit to provide a frequency reference. Both the ground-based simulation subsystem and the space-based simulation subsystem are used for signal generation, transmission, reception, and processing, as well as time delay simulation at the equipment layer and the space transmission layer; the ground-based simulation subsystem is also used for time difference measurement and error correction based on the received bidirectional measurement data. Among them, equipment layer errors include clock error, baseband measurement error, RF channel delay error, frequency synthesis error, and antenna phase center offset error; Space transport layer delays and errors include spatial distance delays, atmospheric delays, delays due to general and special relativistic effects, and multipath effect errors.

2. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The integrated processing unit includes: A high-performance computer platform with supporting integrated processing software is used for network-based remote control and display simulation systems, human-computer interaction and data storage, as well as monitoring the workflow and operating conditions in the simulation system, and controlling the collaborative work of various units in the simulation system for telemetry analysis and business data storage and analysis.

3. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The space environment simulation unit includes: A high-performance computer platform with a matching digital simulation model of the space environment; The space environment digital simulation model includes: a spatiotemporal system model, a satellite orbit model, a user trajectory model, an observation data model, a space environment model, a high dynamic model, and a ranging message model; The high-performance computer platform is used to convert the parameters of the digital simulation model of the space environment into the carrier frequency, phase, pseudocode rate and phase modulation parameters of the signal, and then send them to the baseband signal processing unit.

4. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, Also includes: A constant temperature microwave anechoic chamber environment, including a precision temperature-controlled air conditioner and a microwave anechoic chamber; Among them, precision temperature control air conditioners are used to control time delay changes caused by temperature changes; Microwave anechoic chambers are used to reduce signal reflection by absorbing microwaves, thereby eliminating the effects of temperature variations and multipath effects on measurements of the ground-based and space-based analog subsystems.

5. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The baseband signal processing unit includes: High-performance processor, multi-channel ADC and multi-channel DAC; Among them, the high-performance processor is used to complete baseband signal generation, intermediate frequency transmission and reception, and baseband signal reception processing; Multi-channel ADCs and multi-channel DACs have external reference mode and direct clock mode, which can be used to directly drive signals with different baseband symbol rates for analog and reception via an external clock.

6. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The V-band radio frequency unit includes: Up-converter module and down-converter module; The downconversion module is used to complete the receiving filtering, amplification and downconversion processing, while the upconversion module is used to complete the transmitting baseband signal filtering, amplification and upconversion processing.

7. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The frequency synthesis unit is a high-stability microwave frequency source module, used to provide three frequency reference modes: internal reference mode, external reference mode, and external local oscillator mode. The internal reference mode uses an internally integrated high-stability crystal oscillator, the external reference mode uses a 10MHz frequency source provided by the clock unit, and the external local oscillator mode receives a low-phase-noise optically generated microwave frequency source signal from the clock unit.

8. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The clock unit includes at least one of a rubidium clock, a cesium clock, a hydrogen clock, and a photogenerated microwave frequency source, and is used to provide an external clock reference for the frequency synthesis unit.

9. The V-band microwave satellite-to-ground time difference measurement simulation system as described in claim 1, characterized in that, The clock unit can be a clock from the same source or a clock from different sources and independent. The same source mode is used to evaluate the additional noise of the simulation link, and the different source mode is used to evaluate the clock difference between the two ends of the ground-end simulation subsystem and the space-end simulation subsystem.

10. A simulation method for V-band microwave satellite-to-ground time difference measurement, characterized in that, include: In the ground-side simulation subsystem, the configuration file is input or loaded through the space environment simulation software interface of the space environment simulation unit to set the space transmission environment parameters and generate a scene file. The scene file is transmitted to the baseband signal processing unit of the ground-side simulation subsystem via the communication interface through the network protocol. The scene file is then processed based on the simulation algorithm to obtain a baseband signal superimposed with time delay error and space transmission layer error. The simulation algorithm includes at least one of the following: clock difference simulation algorithm, baseband error algorithm, radio frequency channel time delay algorithm, relativistic time delay algorithm, and atmospheric time delay algorithm. The baseband signal, which is superimposed with time delay error and space transmission layer error, is sent to the radio frequency unit. After up-conversion by the radio frequency unit, the power is adjusted by the power control unit to obtain the first signal. The ground-end analog subsystem sends the first signal to the space-end analog subsystem. After receiving the first signal, the signal receiving and processing module of the space-end analog subsystem demodulates the first signal and extracts the first measurement data by the baseband signal processing unit, and transmits the first measurement data to the ground-end analog subsystem via the microwave link. In the space-end simulation subsystem, a second signal is sent to the ground-end simulation subsystem in a manner symmetrical to that of the ground-end simulation subsystem. The ground-end simulation subsystem extracts the second measurement data. Based on the obtained first and second measurement data, a correction algorithm is invoked, and equipment layer errors and time delay errors are deducted according to the space transmission environment parameters in the scenario file to obtain the simulation results of V-band microwave satellite-to-ground time difference measurement.

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