A software satellite two-way comparison method, device and equipment based on an open loop

Abstract

The application discloses a kind of open loop-based software satellite two-way comparison method, device and equipment, the method includes: by preset sampling frequency, satellite signal is sampled, and original satellite signal is obtained;The original satellite signal obtained by sampling is captured by parallel code phase search method, and the coarse value of carrier frequency Doppler shift and C / A code phase are obtained;The data signal captured is tracked using open loop logic, and TOA measurement value is obtained;During the tracking process of data signal, TOA measurement value is solved by high-resolution correlator algorithm and successive interference cancellation algorithm, to complete software satellite two-way comparison according to the solution result. It can eliminate the accumulation of error in signal tracking process by non-continuous, non-feedback demodulation algorithm, reduce the influence of diurnal effect, improve the short-term stability of comparison, integrate high-resolution correlator and successive interference cancellation technology, improve the resolution based on pseudo-random code comparison, reduce multipath interference, eliminate code interference.

Description

Technical Field

[0001] This invention relates to the field of modulation and demodulation technology of satellite signals, specifically to a software-based two-way satellite comparison method, apparatus, and device based on open-loop. Background Technology

[0002] Currently, the international standard time uses Coordinated Universal Time (UTC). UTC boasts extremely high reliability and long-term frequency stability, relying on different types of atomic clocks in different regions of the world, connected through a time comparison network, enabling precise time comparisons between different locations. Satellite two-way time comparison technology (TWSTFT) is one of the most accurate long-distance time and frequency transmission methods. Two stations send modulated time-frequency signals to each other via satellite, while each station measures the arrival time of the other station's signal by referring to its local clock. The time difference between the two stations' reference clocks is determined based on the difference in their measurement results. Due to the symmetry of its transmission path, propagation delays on the link are almost entirely canceled out. The core of satellite two-way comparison is the modulation and demodulation of the time-frequency signals. Using appropriate modulation and demodulation methods can improve the accuracy and stability of the comparison while reducing errors during propagation. The design and implementation of the TWSTFT modem determine the accuracy and stability of the comparison.

[0003] Currently, the main signal modulation and demodulation methods include three types: (1) analog signal-based modems, the main representative of which is the SATRE modem developed by TimeTech; (2) dual pseudo-random code (DPN)-based modems. It consists of an arbitrary waveform generator (AWG), an analog-to-digital (A / D) sampler, and a high-performance personal computer (PC) equipped with an NVIDIA GeForce graphics card. High-speed data transmission between the PC and the AWG and A / D sampler is achieved using a USB interface; (3) carrier-based satellite two-way comparison (TWCP), the main representative of which is the SRS modem developed and designed by NICT. This modem includes a central processing unit (CPU), a field-programmable gate array (FPGA), a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), filters, amplifiers, a phase-locked loop (PLL), and a 1 GHz oscillator (VCSO).

[0004] However, when using the above method to modulate and demodulate satellite signals, there are still the following defects: (1) The comparison results have obvious diurnal effect: the time comparison results of the SATRE modem show periodic changes in daily and nanoseconds - diurnal effect; (2) Poor anti-interference ability and comparison results are easily affected by the environment: in the actual comparison process, the DPN-based modem and the carrier bidirectional comparison in SRS cannot effectively capture under bad weather conditions, and are prone to loss of lock, and cannot obtain effective comparison results; (3) Poor equipment scalability and low concurrency: SATRE uses analog circuits to implement signal modulation and demodulation. Each function requires the design of a special structure and circuit, which results in a long development cycle and high development cost.

[0005] Therefore, those skilled in the art urgently need to develop a new technical solution to address the above problems. Summary of the Invention

[0006] To overcome the problems existing in related technologies, this invention discloses a software-based two-way satellite comparison method, apparatus, and device based on open-loop technology.

[0007] According to a first aspect of the disclosed embodiments of the present invention, an open-loop software-based two-way satellite alignment method is provided, the method comprising:

[0008] The satellite signal is sampled at a preset sampling frequency to obtain the original satellite signal;

[0009] The original satellite signal obtained by sampling is captured by a parallel code phase search method to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0010] The captured data signal is tracked using open-loop logic to obtain the TOA measurement value;

[0011] During the tracking of the data signal, the TOA measurement value is calculated using a high-resolution correlator algorithm and a continuous interference cancellation algorithm, so as to complete the software satellite two-way comparison based on the calculation results.

[0012] Optionally, the step of capturing the sampled raw satellite signal using a parallel code phase search method to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase includes:

[0013] The original satellite model is downconverted to baseband based on the pre-configured center frequency and Doppler shift value of the data channel;

[0014] Obtain the time-domain data from downconversion to baseband, and obtain the frequency-domain data of baseband through fast Fourier transform;

[0015] The maximum power value and the corresponding frequency position are obtained by multiplying the frequency domain data obtained from the original satellite model with the pre-calculated PRN code frequency domain data.

[0016] The maximum power value and the corresponding frequency position are subjected to TFFT transformation to obtain the convolution result of the original satellite model and the PRN code of the data channel in the time domain.

[0017] The PRN code phase value and signal power are recorded to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0018] Optionally, recording the PRN code phase value and signal power to obtain a coarse value of the carrier frequency Doppler shift and the C / A code phase includes:

[0019] The PRN code phase value and signal power are recorded, and the pre-configured center frequency of the data channel is adjusted according to the signal search frequency range and the signal search frequency step size.

[0020] The process of downconverting the original satellite model to baseband based on the pre-configured center frequency and Doppler shift value of the data channel is repeated until the maximum recorded signal power matches the power value of the reference signal of the data channel. The loop stops then, so as to enter the signal tracking stage based on the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0021] Optionally, the step of using open-loop logic to track the captured data signal and obtain the TOA measurement value includes:

[0022] A preset PRN waveform with a fixed code phase is generated using the OL comparison method;

[0023] The fixed code phase in the preset PRN waveform is correlated with the captured data signal to obtain the TOA measurement value.

[0024] Optionally, the step of associating the fixed code phase in the preset PRN waveform with the captured data signal to obtain the TOA measurement value includes:

[0025] The number of chips is m. The captured data signal is correlated with the k-th waveform in the preset PRN waveform to obtain the correlation result y[k;m].

[0026] The maximum correlation value is labeled as K. Based on the symmetric characteristics of the autocorrelation function of the preset PRN waveform, five maximum correlation results y1[K-2;m], y2[K-1;m], y3[K;m], y4[K+1;m], and y5[K+2;m] are obtained through fitting, thus obtaining the maximum TOA measurement value of the m-th code segment.

[0027] Ts represents the local timescale of the satellite station, and TOA represents the satellite's time of arrival.

[0028] Optionally, the high-resolution correlator algorithm includes:

[0029] Set the number of high-resolution correlators to 5 to improve the local PRN chip resolution.

[0030] Optionally, the continuous interference cancellation algorithm includes:

[0031] When sampling satellite signals, the signal data corresponding to other channels in the original sampling data are deleted.

[0032] According to a second aspect of the embodiments disclosed in this invention, an open-loop software-based two-way satellite comparison device is provided, the device comprising:

[0033] The raw signal acquisition module samples the satellite signal at a preset sampling frequency to acquire the raw satellite signal;

[0034] The signal acquisition module is connected to the original signal acquisition module. It acquires the sampled original satellite signal through a parallel code phase search method to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0035] The signal tracking module is connected to the signal capture module and uses open-loop logic to track the captured data signal to obtain the TOA measurement value.

[0036] The two-way comparison module, connected to the signal tracking module, calculates the TOA measurement value through a high-resolution correlator algorithm and a continuous interference cancellation algorithm during the tracking of the data signal, so as to complete the software satellite two-way comparison based on the calculation result.

[0037] According to a third aspect of the embodiments disclosed in this invention, an open-loop software satellite bidirectional comparison device is provided, the device comprising: a physical layer, a control layer, and a data processing layer;

[0038] The physical layer and the control layer communicate via a network protocol / USB bus protocol, and the control layer and the data processing layer communicate via a vertical protocol.

[0039] Optionally, the physical layer includes: an antenna, a filter, an analog-to-digital converter, a digital-to-analog converter, a device control unit, and a data transmission channel;

[0040] The antenna is used to receive / transmit analog signals;

[0041] The filter is used to perform bandpass filtering on the analog signal;

[0042] The analog-to-digital conversion unit is used to sample analog signals and generate digital signal data;

[0043] The digital-to-analog converter unit is used to convert digital signals into analog signals;

[0044] The device control unit is used to set the device's operating mode, signal filtering bandwidth, sampling rate, center frequency, and signal gain.

[0045] The data transmission channel is used to transmit the digital signal generated by the analog-to-digital converter to the control layer, and to transmit the digital signal generated by the control layer to the digital-to-analog converter.

[0046] In summary, the technical solutions disclosed in the embodiments of the present invention can bring the following beneficial effects:

[0047] (1) An open-loop digital signal tracking logic is proposed to reduce the impact of the daily effect: the original digital signal is obtained by sampling the signal at a sampling frequency far exceeding the code rate. All known signals are captured using CUDA logic and local configuration information. The captured signals are tracked using open-loop logic, and the TOA value is calculated. This avoids the accumulation and propagation of errors caused by unstable signal quality and reduces the impact of the daily effect.

[0048] (2) The integration of multiple interference cancellation algorithms improves the accuracy and precision of the alignment: The integration of the high resolution correlator (HRC) algorithm and the continuous interference cancellation (SIC) algorithm during the tracking process further improves the accuracy and precision of the alignment results.

[0049] (3) Improved concurrency and scalability of comparison: By adopting CUDA-based objectification to realize the concurrent processing of multiple signals, the concurrency of comparison is improved; at the same time, the objectified structure can ensure the scalability of the system and provide a standardized interface for the processing logic of different types of signals.

[0050] (4) Software-based design reduces development costs and time, while facilitating the design and implementation of new modulation and demodulation methods: By establishing an open software framework, it can respond quickly to changes in hardware devices without requiring specialized knowledge of hardware design and FPGA development, thus reducing learning costs. When new signal transmission technologies emerge, there is no need to change the system structure or other layer logic; only new logic and algorithms need to be added laterally to the data processing layer to quickly enter the experimental verification stage, reducing the R&D cycle. The lower learning cost and flexible scalability can strongly promote the rapid development of TWSTFT community technology.

[0051] Other features and advantages disclosed in this invention will be described in detail in the following detailed description section. Attached Figure Description

[0052] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0053] Figure 1 This is a flowchart illustrating an open-loop software-based two-way satellite alignment method according to an exemplary embodiment;

[0054] Figure 2 It is based on Figure 1 A flowchart illustrating a signal capture method is shown.

[0055] Figure 3 It is based on Figure 1 A flowchart illustrating a data signal tracking method is shown.

[0056] Figure 4 It is based on Figure 1 A schematic diagram illustrating the working principle of a high-resolution correlator is shown.

[0057] Figure 5 This is a structural block diagram of an open-loop software satellite bidirectional comparison device according to an exemplary embodiment;

[0058] Figure 6 This is a schematic diagram illustrating the structure of an open-loop software-based satellite bidirectional comparison device according to an exemplary embodiment;

[0059] Figure 7 It is based on Figure 6 The diagram shows the overall software design of an open-loop software-based satellite bidirectional comparison device. Detailed Implementation

[0060] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present disclosure.

[0061] Figure 1 This is a flowchart illustrating an open-loop software-based two-way satellite alignment method according to an exemplary embodiment, such as... Figure 1 As shown, the method includes:

[0062] In step 101, the satellite signal is sampled at a preset sampling frequency to obtain the original satellite signal.

[0063] For example, the original digital signal is obtained by sampling the signal at a sampling frequency that far exceeds the code rate.

[0064] In step 102, the sampled original satellite signal is captured by the parallel code phase search method to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0065] For example, signal acquisition is used to detect visible signals and estimate the carrier Doppler shift and the coarse value of the PRN code (pseudo-random noise code) code phase. In the embodiments disclosed in this invention, the sampled raw satellite signal is acquired using a parallel code phase search method. The C / A code phase search is parallelized into a one-time operation in each Doppler shift search step by utilizing the multiplication-convolution duality property. The C / A code is a pseudo-random code emitted by GPS satellites, used for coarse ranging and GPS satellite acquisition; it is actually a Gold code, generated by a G code consisting of two 10-stage feedback shift registers.

[0066] Figure 2 It is based on Figure 1 The diagram shown is a flowchart of a signal acquisition method, such as... Figure 2 As shown, step 102 includes:

[0067] In step 1021, the original satellite model is downconverted to baseband according to the pre-configured center frequency and Doppler shift value of the data channel.

[0068] In step 1022, the time-domain data of downconversion to baseband is obtained, and the frequency-domain data of baseband is obtained through fast Fourier transform.

[0069] For example, the time-domain data is obtained by downconverting to baseband and the frequency-domain data of baseband is obtained using FFT (Fast Fourier Transform).

[0070] In step 1023, the frequency domain data obtained based on the original satellite model is multiplied by the pre-calculated PRN code frequency domain data to obtain the maximum power value and the corresponding frequency position.

[0071] For example, by multiplying the sampled frequency domain data with the pre-calculated PRN code frequency domain data, the maximum power value and the frequency position corresponding to the maximum power can be obtained.

[0072] In step 1024, the maximum power value and the corresponding frequency position are subjected to TFFT transformation to obtain the time domain convolution result of the original satellite model and the PRN code of the data channel.

[0073] For example, performing a TFFT on the multiplied data (TFFT means that FFT takes real numbers as input and outputs amplitude and phase) can yield the convolution result of the sampled data and the PRN code of that channel in the time domain (multiplying in the frequency domain is equivalent to performing convolution in the time domain).

[0074] In step 1025, the PRN code phase value and signal power are recorded to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0075] Specifically, the PRN code phase value and signal power are recorded, and the pre-configured center frequency of the data channel is adjusted according to the signal search frequency range and the frequency step size of the signal search. The process of downconverting the original satellite model to baseband according to the pre-configured center frequency and Doppler shift value of the data channel and recording the PRN code phase value and signal power is repeated until the maximum recorded signal power meets the power value of the reference signal of the data channel. The loop stops when the maximum recorded signal power meets the power value of the reference signal of the data channel. The signal tracking stage is then entered based on the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0076] For example, if the sampled signal contains data corresponding to the PRN code of the current channel, the time-domain convolution can be equivalent to the autocorrelation operation. The peak value when the sampled data PRN code is aligned with the local PRN copy (τ=0) can be obtained from the calculation result. The index position corresponding to the peak value is the PRN code phase value.

[0077] Based on the signal search frequency range and frequency step size, continuously adjust the center frequency and repeat the above process to acquire and record the code phase value and signal power. After the entire loop is completed, determine whether the maximum signal power matches the power value of the reference signal in the channel configuration information. If it matches, it means that the signal acquisition was successful, and the signal tracking stage begins.

[0078] In step 103, the captured data signal is tracked using open-loop logic to obtain the TOA measurement value.

[0079] For example, after obtaining the coarse value of the carrier frequency Doppler shift and the C / A code phase during signal acquisition, the signal tracking phase will begin. The main purpose of the signal tracking phase is to track the aforementioned coarse value of the carrier frequency Doppler shift and the C / A code phase, extract the message from the signal using them, and provide an estimate for PRN alignment.

[0080] Specifically, Figure 3 It is based on Figure 1 The diagram shows a flowchart of a data signal tracking method, as follows: Figure 3 As shown, step 103 includes:

[0081] In step 1031, a preset PRN waveform with a fixed code phase is generated by the OL comparison method.

[0082] In step 1302, the fixed code phase in the preset PRN waveform is correlated with the captured data signal to obtain the TOA measurement value.

[0083] Specifically, with m chips, the captured data signal is correlated with the k-th waveform in the preset PRN waveform to obtain the correlation result y[k;m]. The maximum correlation value is marked as K. Based on the symmetry of the autocorrelation function of the preset PRN waveform, five maximum correlation results y1[K-2;m], y2[K-1;m], y3[K;m], y4[K+1;m], and y5[K+2;m] are obtained through fitting, thus obtaining the maximum TOA measurement value of the m-th chip segment. Ts represents the local timescale of the satellite station, and TOA represents the satellite's time of arrival.

[0084] For example, the specific steps of the OL-based alignment method are as follows: Generate a set of predetermined PRN code waveforms with fixed code phases, where each code phase is an integer multiple of the sampling period. The high-frequency sampled signal is correlated with all predetermined code phases, and correlated with the k-th waveform after m chips, producing a correlation result y[k;m]. Further, the maximum correlation value is found and denoted as K in the correlation results. To obtain more accurate measurement results, the symmetry of the PRN waveform's autocorrelation function can be utilized, and the maximum TOA measurement value of the m-th code segment can be obtained by fitting five maximum correlation results y1[K-2;m], y2[K-1;m], y3[K;m], y4[K+1;m], and y5[K+2;m].

[0085] In step 104, during the tracking of the data signal, the TOA measurement value is calculated using a high-resolution correlator algorithm and a continuous interference cancellation algorithm, so as to complete the software satellite two-way comparison based on the calculation results.

[0086] The high-resolution correlator algorithm includes setting the number of high-resolution correlators to 5 to improve the resolution of the local PRN chip.

[0087] For example, multipath interference and inter-symbol interference are eliminated by utilizing high-resolution correlator (HRC) technology and continuous interference cancellation (SIC) algorithm. This improves alignment accuracy while reducing the impact of diurnal effects.

[0088] High-resolution correlator (HRC) technology improves the accuracy of autocorrelation calculations by increasing the resolution of the local PRN chip (through increasing the sampling rate), thereby reducing measurement errors caused by multipath effects and improving alignment accuracy. HRC multipath suppression requires more correlators than the three correlators in a typical receiver, generally at least five. This technique requires a narrow lead-hysteresis correlator spacing (d) and a relatively high sampling rate, necessitating a wide receiver front-end bandwidth design to achieve optimal results. The working principle of HRC is as follows... Figure 4 As shown: through the formula This will yield results with higher accuracy.

[0089] The continuous interference cancellation algorithm includes deleting signal data corresponding to other channels in the original sampled data when sampling satellite signals.

[0090] Since the original sampled data contains signal information from multiple channels, the PRN codes between channels can cause inter-symbol interference, affecting the accuracy of the alignment results. The core of the Continuous Interference Cancellation (SIC) algorithm is to delete the signal data corresponding to other channels from the original sampled data and use a "cleaner" signal for processing, thereby improving the accuracy of the alignment.

[0091] Figure 5 This is a structural block diagram of an open-loop software satellite bidirectional comparison device according to an exemplary embodiment, such as... Figure 5 As shown, the device 500 includes:

[0092] The raw signal acquisition module 510 samples the satellite signal at a preset sampling frequency to acquire the raw satellite signal;

[0093] The signal acquisition module 520 is connected to the original signal acquisition module 510. It acquires the sampled original satellite signal through a parallel code phase search method and obtains the coarse value of the carrier frequency Doppler shift and the C / A code phase.

[0094] The signal tracking module 530 is connected to the signal capture module 520 and uses open-loop logic to track the captured data signal to obtain the TOA measurement value.

[0095] The two-way comparison module 540 is connected to the signal tracking module 530. During the tracking of the data signal, the TOA measurement value is calculated using a high-resolution correlator algorithm and a continuous interference cancellation algorithm to complete the software satellite two-way comparison based on the calculation results.

[0096] Figure 6 This is a schematic diagram illustrating the structure of an open-loop software-based satellite bidirectional comparison device according to an exemplary embodiment, such as... Figure 6 As shown, the device includes a physical layer 610, a control layer 620, and a data processing layer 630; the physical layer 610 and the control layer 620 are connected via a network protocol / USB bus protocol, and the control layer 620 and the data processing layer 630 are connected via a vertical protocol.

[0097] The physical layer 610 includes: an antenna, a filter, an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a device control unit, and a data transmission channel; the antenna is used to receive / transmit analog signals; the filter is used to perform bandpass filtering on the analog signals; the ADC is used to sample the analog signals and generate digital signal data; the DAC is used to convert the digital signals into analog signals; the device control unit is used to set the device's operating mode, signal filtering bandwidth, sampling rate, center frequency, and signal gain; the data transmission channel is used to transmit the digital signals generated by the ADC to the control layer, and to transmit the digital signals generated by the control layer to the DAC.

[0098] in addition, Figure 7 It is based on Figure 6 The diagram shown is a general software design block diagram of an open-loop software-based satellite bidirectional comparison device, as follows: Figures 6-7 As shown, the specific principle of this software-satellite two-way comparison device is as follows:

[0099] Configuration management information loading includes system information loading, sampling information loading, system limitation information loading, PRN code information loading, and channel information loading. Pre-configured information allows for flexible control over different demodulation methods, the number of demodulation channels, and the flexible configuration and use of physical layer devices. Specifically, configuration management information loading includes: system information loading, sampling information loading, PRN code information loading, and channel information loading.

[0100] The system information loading process includes: retrieving the working mode flags from the configuration file and saving them to memory. Flag 0 indicates that sampled data is acquired from the physical layer for real-time processing; flag 1 indicates that pre-sampled data is read from a specified location for processing; flag 2 indicates that sampled data is acquired from the physical layer and saved to a file at a specified location, providing support for experiments and verification comparisons of different demodulation methods. It also retrieves information from the configuration file regarding the location of the sampled data file and saves it to memory (used when working mode 1). It retrieves information from the configuration file regarding the location of the saved sampled data and saves it to memory (used when working mode 2). Finally, it retrieves the location information of the comparison result output file and saves it to memory (used when working mode 0 or 1).

[0101] Sampling Information Loading: Obtain the configuration information required for the operation of physical layer devices and save it to memory. This information includes: device location information (network devices can be identified by their IP address, and USB devices by their serial number), sub-device information, sampling rate, sampling data type (sc8, sc16, fc32, fc64), signal center frequency, signal gain, and filtering bandwidth.

[0102] PRN code information loading: Retrieves general PRN code information during system operation and saves it to memory. This includes information such as PRN code type, PRN code length, and code rate.

[0103] Channel Information Loading: Retrieves the configuration information of each station's corresponding channel and saves it to memory. Each channel contains the following information: station name (used to mark the station to which different results belong in the comparison result output), signal receiving channel, observation mode (whether to enable the SCI algorithm to eliminate inter-symbol interference), station's corresponding PRN code number (different stations use different PRN codes to achieve code division multiple access signal transmission), center frequency of the current station's signal, current station's PRN code rate, stage frequency of the current station's corresponding signal, carrier frequency search range during acquisition, initial carrier frequency search step size during acquisition, and SNR of the current channel when the acquisition conditions are met.

[0104] In addition, the physical layer logic is designed in detail. This layer corresponds to the physical layer of the hardware architecture and is mainly responsible for the initialization of hardware devices, the establishment of transceiver channels, and the generation and transmission of digital signals. This layer has different implementation methods for different types of devices.

[0105] Hardware initialization: The device initialization process involves acquiring the sampling information saved in memory by the configuration management logic and configuring the device's operating parameters according to the specific device. Common configuration includes: receiver terminal selection, device frequency source configuration (10MHz signal source), device time source configuration (1PPS signal source), device sampling rate configuration, corresponding center frequency configuration during sampling, device sampling signal gain configuration, device sampling signal filtering bandwidth setting, and sampling data type (sc8, sc16, fc32, fc64) setting.

[0106] The establishment of transceiver channels and the generation and transmission of digital signals: After configuration, a signal receiving channel can be created, the data stream from the receiving channel can be acquired, and it can be saved to a pre-allocated memory space. Each memory space stores one second of sampled data and the timestamp corresponding to the current data. The system uses thread locks and multi-pointer loops to implement data transfer with the control layer logic.

[0107] Furthermore, the detailed design of the control layer logic corresponds to the control layer of the hardware architecture, and is mainly responsible for the initialization, logic calls, data flow, and resource monitoring and allocation of other layers in the system.

[0108] System Initialization: Upon system startup, the configuration management logic is first invoked to objectify all configuration information in the configuration file and save it to memory for use by various functional modules within the system. Different working modes are entered based on the corresponding flags in the configuration information. When the flag is 0, it indicates the current mode is real-time data processing. In this mode, the physical layer logic and data processing layer logic are connected to achieve real-time signal comparison. This also requires invoking the initialization logic of the physical layer hardware devices, acquiring signal data, invoking channel initialization logic, and calling relevant algorithms in the data processing layer logic. When the flag is 1, it indicates the current mode is historical data processing. In this mode, historical sampling data is acquired based on the location specified in the configuration information for saving sampled data. This data is then transmitted to the data processing layer to achieve comparison operations based on historical sampling data. This also requires invoking the channel initialization logic and relevant algorithms in the data processing layer logic. Additionally, the initialization logic of the physical layer hardware devices and signal data acquisition are also invoked.

[0109] Channel initialization: Based on the information in the channel configuration, this process configures the initial parameters for each channel, allocates corresponding memory space, and generates the corresponding PRN code data for each channel. Channel initialization parameters include: pseudo-random code number, pseudo-random code length, sampling rate, whether it is the first tracking attempt, whether tracking has started, code phase delay, initial carrier frequency, integer part of the carrier frequency, fractional part of the carrier frequency, code phase delay rate, carrier phase (unit: cycles), last acquired carrier phase, signal peak value, reference signal power, signal frequency range, frequency step size for signal search, search start frequency, search end frequency, average signal power, maximum value index, and number of processing nodes.

[0110] Memory space allocation mainly includes two aspects: First, the allocation of local memory space, which mainly includes the memory space needed to store the original sampled data. Second, the allocation of CUDA memory space, which mainly includes the storage of the original sampled data, pseudo-random code sequence values, waveform data of the pseudo-random code in the time domain, data converted from sampled data to the frequency domain, and waveform data of sampled data in the frequency domain.

[0111] Each channel generates corresponding PRN code data based on the corresponding station encoding and code length. The generated data is placed into the memory space corresponding to the pseudo-random code sequence value. At the same time, an FFT operation is performed on the PRN code data, and the generated data is placed into the storage space corresponding to the waveform data of the code in the frequency domain.

[0112] Data flow: Data transfer between the data processing layer and the control layer logic is achieved using thread locks and multi-pointer loops, or by retrieving sampled data from a sample file based on configuration. Each channel uses the same sampled data, and this data is read-only. Therefore, the sampled data needs to be placed in CUDA memory, which stores the original sampled data and is shared by all channels. After the data processing layer completes its corresponding calculations, the result data in CUDA is copied to the control layer in one go. The control layer is then responsible for outputting the result data to a specified file.

[0113] In summary, the technical solutions disclosed in the embodiments of the present invention can bring the following beneficial effects:

[0114] (1) An open-loop digital signal tracking logic is proposed to reduce the impact of the daily effect: the original digital signal is obtained by sampling the signal at a sampling frequency far exceeding the code rate. All known signals are captured using CUDA logic and local configuration information. The captured signals are tracked using open-loop logic, and the TOA value is calculated. This avoids the accumulation and propagation of errors caused by unstable signal quality and reduces the impact of the daily effect.

[0115] (2) The integration of multiple interference cancellation algorithms improves the accuracy and precision of the alignment: The integration of the high resolution correlator (HRC) algorithm and the continuous interference cancellation (SIC) algorithm during the tracking process further improves the accuracy and precision of the alignment results.

[0116] (3) Improved concurrency and scalability of comparison: By adopting CUDA-based objectification to realize the concurrent processing of multiple signals, the concurrency of comparison is improved; at the same time, the objectified structure can ensure the scalability of the system and provide a standardized interface for the processing logic of different types of signals.

[0117] (4) Software-based design reduces development costs and time, while facilitating the design and implementation of new modulation and demodulation methods: By establishing an open software framework, it can respond quickly to changes in hardware devices without requiring specialized knowledge of hardware design and FPGA development, thus reducing learning costs. When new signal transmission technologies emerge, there is no need to change the system structure or other layer logic; only new logic and algorithms need to be added horizontally in the data processing layer to quickly enter the experimental verification stage, reducing the R&D cycle. The lower learning cost and flexible scalability can strongly promote the rapid development of TWSTFT community technology.

[0118] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0119] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0120] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A software-based two-way satellite alignment method based on open-loop, characterized in that, The method includes: The satellite signal is sampled at a preset sampling frequency to obtain the original satellite signal; The original satellite signal obtained by sampling is captured by a parallel code phase search method to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase. The captured data signal is tracked using open-loop logic to obtain the TOA measurement value; During the tracking of the data signal, the TOA measurement value is calculated using a high-resolution correlator algorithm and a continuous interference cancellation algorithm, so as to complete the software satellite two-way comparison based on the calculation results; The process of capturing the sampled raw satellite signal using a parallel code phase search method to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase includes: The original satellite model is downconverted to baseband based on the pre-configured center frequency and Doppler shift value of the data channel; Obtain the time-domain data from downconversion to baseband, and obtain the frequency-domain data of baseband through fast Fourier transform; The maximum power value and the corresponding frequency position are obtained by multiplying the frequency domain data obtained from the original satellite model with the pre-calculated PRN code frequency domain data; The maximum power value and the corresponding frequency position are subjected to TFFT transformation to obtain the convolution result of the original satellite model and the PRN code of the data channel in the time domain. The PRN code phase value and signal power are recorded to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase; The recording of PRN code phase values ​​and signal power to obtain coarse values ​​of carrier frequency Doppler shift and C / A code phase includes: The PRN code phase value and signal power are recorded, and the pre-configured center frequency of the data channel is adjusted according to the signal search frequency range and the signal search frequency step size. The process of downconverting the original satellite model to baseband based on the pre-configured center frequency and Doppler shift value of the data channel is repeated until the maximum recorded signal power matches the power value of the reference signal of the data channel. The loop stops then, so as to enter the signal tracking stage based on the coarse value of the carrier frequency Doppler shift and the C / A code phase.

2. The software-based two-way satellite comparison method based on open-loop as described in claim 1, characterized in that, The step of using open-loop logic to track the captured data signal and obtain the TOA measurement value includes: A preset PRN waveform with a fixed code phase is generated using the OL comparison method; The fixed code phase in the preset PRN waveform is correlated with the captured data signal to obtain the TOA measurement value.

3. The software-based two-way satellite comparison method based on open-loop as described in claim 2, characterized in that, The step of associating the fixed code phase in the preset PRN waveform with the captured data signal to obtain the TOA measurement value includes: The number of chips is m. The captured data signal is correlated with the k-th waveform in the preset PRN waveform to obtain the correlation result y[k;m]. The maximum correlation value is labeled as K. Based on the symmetric characteristics of the autocorrelation function of the preset PRN waveform, five maximum correlation results y1[K-2;m], y2[K-1;m], y3[K;m], y4[K+1;m], and y5[K+2;m] are obtained through fitting, thus obtaining the maximum TOA measurement value of the m-th code segment. T s The local time scale of the satellite station is indicated by TOA, which represents the satellite's time of arrival.

4. The open-loop software satellite bidirectional comparison method according to claim 1, wherein the high-resolution correlator algorithm comprises: Set the number of high-resolution correlators to 5 to improve the local PRN chip resolution.

5. The open-loop software-based two-way satellite comparison method according to claim 1, wherein the continuous interference cancellation algorithm comprises: When sampling satellite signals, the signal data corresponding to other channels in the original sampling data are deleted.

6. A software-based two-way satellite comparison device based on open-loop, characterized in that, The device includes: The raw signal acquisition module samples the satellite signal at a preset sampling frequency to acquire the raw satellite signal; The signal acquisition module, connected to the original signal acquisition module, acquires the sampled original satellite signal using a parallel code phase search method, obtaining the coarse value of the carrier frequency Doppler shift and the C / A code phase; it down-converts the original satellite signal to baseband based on the pre-configured center frequency and Doppler shift value of the data channel; it acquires the time-domain data of the down-converted baseband signal and the frequency-domain data of the baseband signal using a fast Fourier transform; it multiplies the frequency-domain data obtained based on the original satellite signal with the pre-calculated PRN code frequency-domain data to obtain the maximum power value and the corresponding frequency position; it then performs a TFFT transform on the maximum power value and the corresponding frequency position to obtain the time-domain data of the sampled original satellite signal and the PRN code of the data channel. The convolution result of the domain; record the PRN code phase value and signal power to obtain the coarse value of the carrier frequency Doppler shift and the C / A code phase; record the PRN code phase value and signal power, and adjust the pre-configured center frequency of the data channel according to the search frequency range and the frequency step size of the signal search; repeat the process of downconverting the original satellite model to the baseband according to the pre-configured center frequency and Doppler shift value of the data channel, and recording the PRN code phase value and signal power, until the maximum recorded signal power meets the power value of the reference signal of the data channel and the loop stops, so as to enter the signal tracking stage according to the obtained coarse value of the carrier frequency Doppler shift and the C / A code phase; The signal tracking module is connected to the signal capture module and uses open-loop logic to track the captured data signal to obtain the TOA measurement value. The two-way comparison module, connected to the signal tracking module, calculates the TOA measurement value through a high-resolution correlator algorithm and a continuous interference cancellation algorithm during the tracking of the data signal, so as to complete the software satellite two-way comparison based on the calculation result.

7. A software-based two-way satellite comparison device based on open-loop, characterized in that, The device, which is applied to an open-loop software-based two-way satellite comparison method as described in any one of claims 1 to 5, comprises: a physical layer, a control layer, and a data processing layer; The physical layer and the control layer communicate via a network protocol / USB bus protocol, and the control layer and the data processing layer communicate via a vertical protocol. The physical layer includes: antenna, filter, analog-to-digital converter, digital-to-analog converter, device control unit, and data transmission channel; The antenna is used to receive / transmit analog signals; The filter is used to perform bandpass filtering on the analog signal; The analog-to-digital conversion unit is used to sample analog signals and generate digital signal data; The digital-to-analog converter unit is used to convert digital signals into analog signals; The device control unit is used to set the device's operating mode, signal filtering bandwidth, sampling rate, center frequency, and signal gain. The data transmission channel is used to transmit the digital signal generated by the analog-to-digital converter to the control layer, and to transmit the digital signal generated by the control layer to the digital-to-analog converter.

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