A method and system for distributed acquisition and centralized synchronous playback of GNSS signals

Abstract

The application relates to a GNSS signal distributed collection and centralized synchronous playback method and system, which comprises the following steps: collecting long baseline or short baseline GNSS signals and carrying out radio frequency signal digitization processing; reading the data of n collection storage units into a data processing system for data synchronous truncation, then processing and calculating the data of each collection storage unit; reconstructing the sampling signals to compensate clock errors in the sampling process, then filtering and up-converting the reconstructed signals, modulating the GNSS signals input from different channels to corresponding frequencies to form radio frequency signals, and transmitting the multi-frequency radio frequency GNSS signals out through a multiplexer. The application can centrally and synchronously play back the collection signals containing clock errors, reproduce the time-frequency characteristics of the GNSS radio frequency signals at the collection time, and avoid the influence of the clock errors of the collection device on the test results of the synchronous equipment.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a method and system for distributed acquisition and centralized synchronous playback of GNSS signals. Background Technology

[0002] Conventional navigation terminal testing techniques can be categorized into three types based on their implementation: GNSS actual signal testing, GNSS analog signal testing, and GNSS signal acquisition and playback testing. GNSS actual signal testing is susceptible to high dynamics and complex electromagnetic environments, resulting in poor repeatability and high costs. While GNSS analog signal testing can simulate precise and controllable GNSS signals indoors to verify navigation terminal performance and test the theoretical limits of algorithms, the simulated signals are too idealistic to accurately depict the complex and ever-changing real-world environment, and the test results cannot accurately assess the actual performance of the navigation terminal. In contrast, GNSS signal acquisition and playback testing, by acquiring, storing, and replaying actual GNSS signals, ensures both signal authenticity and test repeatability, effectively completing the practical performance testing of satellite navigation terminals at a lower time and cost.

[0003] However, most existing GNSS signal acquisition and playback equipment is single-channel, which cannot meet the needs of distributed acquisition and centralized playback. In addition, existing acquisition and playback equipment only acquires, stores, and plays back GNSS signals without synchronizing the acquired data. This makes it impossible to synchronize the playback of multiple acquired signals, which introduces additional clock errors into the acquired signals during centralized playback, seriously affecting the test results of synchronization equipment. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for distributed acquisition and centralized synchronous playback of GNSS signals, thus solving the deficiencies of the prior art.

[0005] The objective of this invention is achieved through the following technical solution: a method for distributed acquisition and centralized synchronous playback of GNSS signals, wherein the synchronous playback method includes:

[0006] Distributed acquisition steps: GNSS signals of long or short baselines are acquired by n acquisition and storage units placed in different spatial locations, and radio frequency signals are digitized.

[0007] Information centralized processing steps: Read the data from n acquisition and storage units into the data processing system for data synchronization and truncation to ensure that the starting data of each channel is synchronized to the same moment, and then process and calculate the data of each acquisition and storage unit.

[0008] Synchronous playback steps: The sampled signal is reconstructed to compensate for the clock error during the sampling process. Then, the reconstructed signal is filtered and up-converted to modulate the GNSS signals input from different channels to the corresponding frequencies to form radio frequency signals. The multi-frequency radio frequency GNSS signals are then synthesized by a multiplexer and transmitted from the radio frequency port.

[0009] The centralized information processing steps specifically include the following:

[0010] Calculate the start and end times of n GNSS signals acquired by n acquisition and storage units, determine the maximum start time and minimum end time, and perform data synchronization segments to save the acquired data with the same start and end time.

[0011] The signals from each acquisition and storage unit are demodulated and decoded to obtain GNSS pseudorange, carrier observations, and broadcast ephemeris. Precise ephemeris, zenith tropospheric correction files, Earth rotation parameter files, Earth tidal correction files, phase fractional bias files, and satellite antenna files are downloaded from the IGS analysis center. Then, an ionospheric-free combined model is constructed using the aforementioned observations and ephemeris files, and errors are corrected using the various error correction files. Finally, a Kalman filter algorithm is used to estimate position, velocity, and clock bias epoch-by-epoch to obtain clock bias data, i.e., the clock bias sequence Δt for each acquisition and storage unit. i (i = 1, 2, ..., n);

[0012] The aligned data and the calculated clock difference sequence are stored in a file for synchronization control and duration control of GNSS signal playback.

[0013] The synchronous playback step specifically includes the following:

[0014] The GNSS digital baseband signal is converted from digital to analog, and the clock difference sequence Δt is obtained by post-processing PPP. i (i = 1, 2, ..., n) Reconstruct the sampled signal to obtain the reconstructed signal. To compensate for clock errors during the sampling process, where e r (t) represents the reconstructed signal, e s (τ+Δt i ) represents the derivative of the actual sampled signal, Δt i The clock error introduced during sampling is h[t-(τ+Δt)]. i [)] is the differential of the corrected interpolation function;

[0015] Then, the reconstructed signal is filtered and up-converted to modulate the GNSS signals input from different channels to the corresponding frequencies to form radio frequency signals. The multi-frequency radio frequency GNSS signals are then synthesized by a multiplexer and transmitted from the radio frequency port.

[0016] A distributed acquisition and centralized synchronous playback system for GNSS signals includes n acquisition and storage units, information processing units, and playback and transmission units arranged in different spatial locations;

[0017] The acquisition and storage unit is used to acquire GNSS signals from long or short baselines at different spatial locations, process them, and then transmit them to the information processing unit.

[0018] The information processing unit receives raw I and Q data from n acquisition and storage units, processes the raw I and Q data to achieve synchronous truncation, demodulation, and decoding of GNSS signals, and downloads precise ephemeris, zenith tropospheric correction files, Earth rotation parameter files, Earth tidal correction files, phase fractional deviation files, and satellite antenna files from the IGS analysis center. Then, it constructs an ionosphere-free combined model using the aforementioned observations and ephemeris files, corrects errors using the various error correction files, and finally estimates position, velocity, and clock bias epoch-by-epoch using a sampling Kalman filter algorithm to obtain clock bias data, i.e., the clock bias sequence Δt for each acquisition and storage unit. i (i = 1, 2, ..., n), the aligned data and the calculated clock difference sequence are stored in a file for synchronization control and duration control of GNSS signal playback;

[0019] The playback and transmission unit is used to reconstruct the sampled signal after it has been processed by the information processing unit to compensate for the clock error during the sampling process. Then, it filters and upconverts the reconstructed signal to modulate the GNSS signals input from different channels to the corresponding frequencies to form radio frequency signals. Finally, it synthesizes the multi-frequency radio frequency GNSS signals through a multiplexer and transmits them out through the radio frequency port.

[0020] The acquisition and storage unit includes a radio frequency front-end processing module, a digital signal processing module, and a memory module;

[0021] The radio frequency front-end processing module is connected to the GNSS antenna. It divides the received signal into four paths through a power divider, then amplifies and mixes the four signals to obtain four I / Q intermediate frequency signals. The four intermediate frequency signals are then filtered to obtain four analog intermediate frequency signals. Finally, the four analog intermediate frequency signals are sampled and converted from analog to digital to obtain digital baseband signals.

[0022] The digital signal processing module is used to filter and frame the digital baseband signal after analog-to-digital conversion.

[0023] The memory module is used to store the filtered and framed digital baseband signal.

[0024] The playback and transmission unit includes a front-end processing module, n radio frequency transmission modules, and n multi-channel signal synthesis modules;

[0025] The front-end processing module is used to acquire the GNSS signal file of the information processing unit and send the n digital GNSS signals to the n radio frequency transmission modules according to the control signals in the file at the set time and frequency.

[0026] The radio frequency transmission module is used to convert four IQ digital GNSS signals from digital to analog and combine them with the calculated clock difference sequence Δt. i (i = 1, 2, ..., n) The sampled signal is reconstructed to compensate for clock errors during the sampling process;

[0027] The multi-channel synthesis module is used to synthesize the multi-frequency GNSS signals generated by the RF transmission module through a multi-channel synthesizer and then transmit them through the RF port.

[0028] It also includes a clock unit, which is used to receive an external reference clock, connect to an analog-to-digital converter to generate a second synchronization signal, and coordinate the time and frequency required for the generation of analog signals.

[0029] This invention has the following advantages: a method and system for distributed acquisition and centralized synchronous playback of GNSS signals, which can meet the synchronization performance evaluation requirements under long / short baseline, multi-node, high / low dynamic or static environments; a synchronization time truncation scheme is provided, so that the playback time of the n playback signals can be unified when the n distributed acquisition signals are played back in a centralized manner; and multiple acquisition signals containing clock errors can be played back synchronously in a centralized manner, reproducing the time-frequency characteristics of the GNSS radio frequency signal at the acquisition time, and avoiding the influence of the clock error of the acquisition device on the test results of the synchronization equipment. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0031] Figure 2 This is a schematic diagram of the data acquisition and storage unit.

[0032] Figure 3 This is a schematic diagram of the playback and transmission unit.

[0033] Figure 4 This is a flowchart illustrating the steps involved in centralized information processing. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application provided below with reference to the accompanying drawings is not intended to limit the scope of protection of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, one embodiment of the present invention relates to a distributed acquisition and centralized synchronous playback system for GNSS (Global Navigation Satellite System) signals. By post-processing the distributed acquisition data, the clock difference for each sample is obtained. During signal reconstruction, the clock difference is compensated, thereby achieving centralized synchronous playback of the distributed acquisition signals to meet the testing requirements of synchronization equipment in long / short baseline, multi-node, high / low dynamic or static environments.

[0036] It includes n acquisition and storage units, information processing units, and playback and transmission units arranged in different spatial locations;

[0037] Acquisition and storage unit: used to acquire GNSS signals from long or short baselines at different spatial locations, process them, and then transmit them to the information processing unit;

[0038] The information processing unit receives raw I and Q data from n acquisition and storage units, processes the raw I and Q data to achieve synchronous truncation, demodulation, and decoding of GNSS signals, and downloads precise ephemeris, zenith tropospheric correction files, Earth rotation parameter files, Earth tidal correction files, phase fractional deviation files, and satellite antenna files from the IGS analysis center. Then, it constructs an ionospheric-free combined model using the above observations and ephemeris files, corrects errors using the various error correction files, and finally estimates position, velocity, and clock bias epoch by epoch using a sampling Kalman filter algorithm to obtain clock bias data, i.e., the clock bias sequence Δt for each acquisition and storage unit. i (i = 1, 2, ..., n), the aligned data and the calculated clock difference sequence are stored in a file for synchronization control and duration control of GNSS signal playback;

[0039] Playback and transmission unit: It is used to reconstruct the sampled signal after it has been processed by the information processing unit to compensate for the clock error in the sampling process. Then, it filters and upconverts the reconstructed signal to modulate the GNSS signals input from different channels to the corresponding frequencies to form radio frequency signals. The multi-frequency radio frequency GNSS signals are then synthesized by a multiplexer and transmitted from the radio frequency port.

[0040] like Figure 2 As shown, the acquisition and storage unit includes an RF front-end processing module, a digital signal processing module, and a memory module;

[0041] The radio frequency front-end processing module is connected to the GNSS antenna. The received signal is divided into four paths by a power divider. The four signals are then amplified and mixed to obtain four I / Q intermediate frequency signals. The four intermediate frequency signals are then filtered to obtain four analog intermediate frequency signals. Finally, the four analog intermediate frequency signals are sampled and converted from analog to digital to obtain digital baseband signals.

[0042] The frequency band coverage, bandwidth, and covered satellite frequencies of each channel are shown in Table 1. The covered frequencies include the full frequencies of the six major constellations: GPS, GALILEO, GLONASS, BDS, QZSS, and IRNSS, as well as the enhanced frequency PPP-B2b of BDS and the full frequencies of the satellite-based augmentation system.

[0043] Table 1. Correspondence between the frequency band range of the four input signals and satellite frequencies.

[0044]

[0045] Ideally, when a continuous signal f(t) is sampled at a sampling rate T, the sampling process can be described as follows:

[0046]

[0047] Among them, e s (nT) is the signal sampled at the nth time, and δ is the Dirac function, which satisfies:

[0048]

[0049] However, in practical applications, the clock of each GNSS signal acquisition unit inevitably has errors, causing the actual sampled signal to not be sampled at strictly equal intervals according to the sampling rate T. Therefore, the actual sampling process is as follows:

[0050]

[0051] Where, Δt nThis represents the clock error of the nth sampling. It's important to note that the clock error introduced during sampling by the acquisition unit will be passed to the signal reconstruction process, preventing true synchronization of the distributed acquisition signals and thus affecting the test results of the synchronized device under test.

[0052] Digital signal processing module: used to filter and frame the digital baseband signal after analog-to-digital conversion;

[0053] Memory module: Used to store the filtered and framed digital baseband signal.

[0054] Furthermore, such as Figure 3 As shown, the playback and transmission unit includes a front-end processing module, n radio frequency transmission modules, and n multi-channel signal synthesis modules;

[0055] Front-end processing module: used to acquire the GNSS signal file of the information processing unit and send the n digital GNSS signals to the n radio frequency transmission modules according to the control signals in the file at the set time and frequency;

[0056] RF Transmitter Module: Used to convert four IQ digital GNSS signals from digital to analog and combine them with the calculated clock difference sequence Δt. i (i = 1, 2, ..., n) The sampled signal is reconstructed to compensate for clock errors during the sampling process;

[0057] Ideally, the refactoring process can be described as follows:

[0058]

[0059] Among them, e r (t) is the reconstructed signal, and h(t-τ) is the interpolation function, with the specific form shown below:

[0060]

[0061] In reality, the sampled signal contains the clock error of each sample. When reconstructing according to equation (1.4), the clock error of the sampled signal will inevitably be introduced into the reconstructed signal. To compensate for the clock error during the sampling process, this invention combines the calculated clock difference sequence Δt i The interpolation function (i = 1, 2, ..., n) is modified so that the reconstruction process can be performed according to the actual sampling time. Then the actual reconstruction process can be described as follows:

[0062]

[0063] The reconstructed signal is then filtered by a filter and then up-converted by a mixer to complete phase calibration. Finally, the IQ and data are combined, and the GNSS signals input from different channels are modulated to the corresponding frequencies according to the channel frequency configuration parameters to form radio frequency signals.

[0064] Multi-channel synthesis module: Used to synthesize the multi-frequency GNSS signals generated by the RF transmitter module through a multi-channel synthesizer and then transmit them through the RF port.

[0065] It also includes a clock unit, which is used to receive an external reference clock, connect to an analog-to-digital converter to generate a second synchronization signal, and coordinate the time and frequency required for the generation of analog signals.

[0066] Another embodiment of the present invention relates to a method for distributed acquisition and centralized synchronous playback of GNSS signals, which specifically includes the following:

[0067] 1. Distributed data collection:

[0068] n acquisition and storage units are placed at n different spatial locations to acquire GNSS signals with either long or short baselines, depending on the specific testing requirements. Each acquisition and storage unit is mounted on different vehicles, including ground surfaces, mountaintops, vehicles, and drones, to obtain GNSS signals under varying altitudes, geographical locations, and motion conditions. Finally, GNSS signal acquisition is performed according to agreed-upon start and end times.

[0069] The acquisition and storage unit primarily performs RF signal digitization processing, including low-noise amplification, mixing, filtering, sampling, and analog-to-digital conversion. To cover the entire GNSS constellation and all frequency points, each acquisition and storage unit is designed with four signal channels. The frequency band coverage, bandwidth, and covered satellite frequencies for each channel are shown in Table 1. The covered frequencies include the full frequencies of the six major constellations: GPS, GALILEO, GLONASS, BDS, QZSS, and IRNSS, as well as the enhanced frequency PPP-B2b of BDS and the full frequencies of the satellite-based augmentation system. Then, the RF-processed digital baseband signal is filtered, framed, and stored. The received GNSS signal is processed according to the required GNSS signal sampling rate and written to the memory module.

[0070] 2. Centralized information processing:

[0071] like Figure 4 As shown, data from n acquisition and storage units is read into the data processing system and the data is synchronized and truncated. That is, the acquisition data with the same start and end time is saved and other data is deleted to ensure that the start data of each channel is synchronized to the same time.

[0072] Then, the signals from each acquisition and storage unit are demodulated and decoded to obtain GNSS pseudorange, carrier observations, and broadcast ephemeris. Precise ephemeris, zenith tropospheric correction files, Earth rotation parameter files, Earth tidal correction files, code offset correction files, phase fractional offset files, and satellite antenna files are downloaded from the IGS analysis center. Then, an ionospheric-free combined model is constructed using the aforementioned observations and ephemeris files, and error correction is performed using the various error correction files. Finally, a Kalman filter algorithm is used to estimate position, velocity, and clock bias epoch-by-epoch to obtain clock bias data, i.e., the clock bias sequence Δt for each acquisition and storage unit. i (i = 1, 2, ..., n).

[0073] Finally, the aligned data and the calculated clock difference sequence are stored in a file for synchronization control and duration control of GNSS signal playback.

[0074] 3. Centralized playback:

[0075] First, the GNSS digital baseband signal is converted from digital to analog, and then combined with the clock difference sequence Δt calculated by post-processing PPP. i (i = 1, 2, ..., n) The sampled signal is reconstructed to compensate for clock errors during the sampling process:

[0076]

[0077] Among them, e r (t) represents the reconstructed signal, e s (τ+Δt i ) represents the derivative of the actual sampled signal, Δt i The clock error introduced during sampling is h[t-(τ+Δt)]. i [)] represents the derivative of the corrected interpolation function. The actual sampled signal and the corrected interpolation function are expressed as follows:

[0078]

[0079]

[0080] Where f(t) is the original continuous signal, Δt n Let δ be the clock error of the nth sampling, and let δ be the Dirac function, satisfying:

[0081]

[0082] Substituting equations (1.8) and (1.9) into equation (1.7) yields the reconstructed signal:

[0083]

[0084] Then, the reconstructed signal is filtered and up-converted to modulate the GNSS signals from different channels to the corresponding frequencies, forming radio frequency (RF) signals. Finally, the multi-frequency RF GNSS signals are combined by a multiplexer and transmitted through the RF port.

[0085] By connecting n devices under test to n ports of the RF transmitting unit, GNSS signals acquired in different spaces can be replayed in the same space, achieving the purpose of simulating long / short baseline, multi-node, high / low dynamic or static environment testing. Users can adjust the equipment structure or optimize the algorithm based on the test results, and then repeat the signal playback to verify the correctness of the adjustment or optimization.

[0086] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and improvements, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for distributed acquisition and centralized synchronous playback of GNSS signals, characterized in that: The synchronous playback method includes: Distributed acquisition steps: GNSS signals of long or short baselines are acquired by n acquisition and storage units placed in different spatial locations, and radio frequency signals are digitized. Information centralized processing steps: Read the data from n acquisition and storage units into the data processing system for data synchronization and truncation to ensure that the starting data of each channel is synchronized to the same moment, and then process and calculate the data of each acquisition and storage unit. Synchronous playback steps: The sampled signal is reconstructed to compensate for the clock error during the sampling process. Then, the reconstructed signal is filtered and up-converted. The GNSS signals input from different channels are modulated to the corresponding frequencies to form radio frequency signals. The multi-frequency radio frequency GNSS signals are combined through a multiplexer and then transmitted from the radio frequency port. The synchronous playback step specifically includes the following: The GNSS digital baseband signal is converted from digital to analog, and the clock bias sequence is then calculated using post-processing PPP. The sampled signal is reconstructed to obtain the reconstructed signal. To compensate for clock errors during the sampling process, where, For the reconstructed signal, The derivative of the actual sampled signal, This is due to clock errors introduced during sampling. The derivative of the corrected interpolation function; Then, the reconstructed signal is filtered and up-converted to modulate the GNSS signals input from different channels to the corresponding frequencies to form radio frequency signals. The multi-frequency radio frequency GNSS signals are then synthesized by a multiplexer and transmitted from the radio frequency port.

2. The method for distributed acquisition and centralized synchronous playback of GNSS signals according to claim 1, characterized in that: The centralized information processing steps specifically include the following: Calculate the start and end times of n GNSS signals acquired by n acquisition and storage units, determine the maximum start time and minimum end time, and perform data synchronization segments to save the acquired data with the same start and end time. The signals from each acquisition and storage unit are demodulated and decoded to obtain GNSS pseudorange, carrier observations, and broadcast ephemeris. Precise ephemeris, zenith tropospheric correction files, Earth rotation parameter files, Earth tidal correction files, phase fractional bias files, and satellite antenna files are downloaded from the IGS analysis center. Then, an ionospheric-free combined model is constructed using the aforementioned observations and ephemeris files, and errors are corrected using the various error correction files. Finally, a Kalman filter algorithm is used to estimate position, velocity, and clock bias epoch-by-epoch, thereby obtaining clock bias data, i.e., the clock bias sequence for each acquisition and storage unit. ; The aligned data and the calculated clock difference sequence are stored in a file for synchronization control and duration control of GNSS signal playback.

3. A distributed acquisition and centralized synchronous playback system for GNSS signals, characterized in that: It includes n acquisition and storage units, information processing units, and playback and transmission units arranged in different spatial locations; The acquisition and storage unit is used to acquire GNSS signals from long or short baselines at different spatial locations, process them, and then transmit them to the information processing unit. The information processing unit receives raw I and Q data from n acquisition and storage units, processes the raw I and Q data to achieve synchronous truncation, demodulation, and decoding of GNSS signals, and downloads precise ephemeris, zenith tropospheric correction files, Earth rotation parameter files, Earth tidal correction files, phase fractional deviation files, and satellite antenna files from the IGS analysis center. Then, it constructs an ionosphere-free combined model using the aforementioned observations and ephemeris files, corrects errors using the various error correction files, and finally estimates position, velocity, and clock bias epoch-by-epoch using a sampling Kalman filter algorithm to obtain clock bias data, i.e., the clock bias sequence of each acquisition and storage unit. The aligned data and the calculated clock difference sequence are stored in a file for synchronization control and duration control of GNSS signal playback; The playback and transmission unit is used to reconstruct the sampled signal after it has been processed by the information processing unit to compensate for the clock error during the sampling process. Then, it filters and upconverts the reconstructed signal to modulate the GNSS signals input from different channels to the corresponding frequencies to form radio frequency signals. Finally, it synthesizes the multi-frequency radio frequency GNSS signals through a multiplexer and transmits them out through the radio frequency port. The playback and transmission unit includes a front-end processing module, n radio frequency transmission modules, and n multi-channel signal synthesis modules; The front-end processing module is used to acquire the GNSS signal file of the information processing unit and send the n digital GNSS signals to the n radio frequency transmission modules according to the control signals in the file at the set time and frequency. The radio frequency transmission module is used to convert four IQ digital GNSS signals from digital to analog and combine them with the calculated clock difference sequence. The sampled signal is reconstructed to compensate for clock errors during the sampling process; Multiplexing module: Used to combine the multi-frequency GNSS signals generated by the RF transmitter module through a multiplexer and then transmit them through the RF port.

4. A GNSS signal distributed acquisition and centralized synchronous playback system according to claim 3, characterized in that: The acquisition and storage unit includes a radio frequency front-end processing module, a digital signal processing module, and a memory module; The radio frequency front-end processing module is connected to the GNSS antenna. It divides the received signal into four paths through a power divider, then amplifies and mixes the four signals to obtain four I / Q intermediate frequency signals. The four intermediate frequency signals are then filtered to obtain four analog intermediate frequency signals. Finally, the four analog intermediate frequency signals are sampled and converted from analog to digital to obtain digital baseband signals. The digital signal processing module is used to filter and frame the digital baseband signal after analog-to-digital conversion. The memory module is used to store the filtered and framed digital baseband signal.

5. A GNSS signal distributed acquisition and centralized synchronous playback system according to claim 3 or 4, characterized in that: It also includes a clock unit, which is used to receive an external reference clock, connect to an analog-to-digital converter to generate a second synchronization signal, and coordinate the time and frequency required for the generation of analog signals.

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