A software-based satellite two-way time comparison modulation system and its use method

Abstract

The present application belongs to the technical field of satellite two-way time comparison. The present application provides a software-based satellite two-way time comparison modulation system and a method of using the same. The loosely coupled design between the modules of the disclosed embodiment can quickly realize the generation of satellite two-way time comparison signals with different precisions, different frequencies, different modulation methods and different coding modes. While ensuring the measurement accuracy and stability, the satellite two-way time comparison modulation system is made flexible and universal, realizing the rapid migration between scientific experiments and practical applications. It can also overcome the problems of high design difficulty, long design cycle and poor flexibility of analog devices and FPGA-based devices.

Description

Technical Field

[0001] The disclosed embodiments relate to the technical field of satellite two-way time comparison, and more particularly to a software-based satellite two-way time comparison modulation system and a method for using the same. Background Art

[0002] Two Way Satellite Time and Frequency Transfer (TWSTFT) is one of the most accurate remote time and frequency transfer methods. By using a reasonable modulation method, the accuracy and stability of the comparison can be improved, and the error in the propagation process can be reduced.

[0003] At present, there are three main signal modulation methods:

[0004] The first is the modulation method based on analog signals, which is mainly represented by the SATRE modem. The modem encodes the local pulse per second signal at the transmitter to generate the time signal of the local atomic clock, and directly spreads the encoded signal through a specified pseudo random code (PRN), and then up-converts the spread baseband signal to a digital intermediate frequency (70MHz) before transmitting.

[0005] The second is the carrier-based satellite two-way comparison (TWCP) modulation method, which is mainly represented by the SRS modem. The 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), a filter, an amplifier, a phase-locked loop (PLL), and a 1 GHz oscillator (VCSO). The frequency of the SRS output signal is 70 MHz. The output signal is formed by a digital bandpass filter, and a 200 MHz DAC converts the digital signal into an analog signal, which is then output after passing through an amplifier and an analog low-pass and bandpass filter. The code rate in the signal is 1 Mbps, and the signal bandwidth is limited to less than 1.3 MHz. The PRN code sequence uses GPS L2C (M-code) with a code length of 20,000 bits. The transmission signal carries 50 bps of data, including the measurement result information of the corresponding site.

[0006] The third is the modulation method based on software defined radio (SDR), which is mainly represented by the TWSTFT modulation system. This system uses the FPGA in the SDR device to up-convert the baseband signal to a digital intermediate frequency (IF), and sends the output signal to the VSAT up-converter after digital-to-analog conversion.

[0007] In the related technologies, the modulation method based on analog signals uses analog circuits to realize signal modulation, and the modulation methods based on carriers and SDR use field programmable gate arrays (FPGAs) to realize baseband signal generation and up-conversion operations. When verifying the effectiveness of different modulation methods, the above two methods cannot achieve fast response, which has an adverse impact on the development and application of two-way time comparison technology.

[0008] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions. Summary of the invention

[0009] In order to avoid the deficiencies of the prior art, the present invention provides a software-based satellite two-way time comparison modulation system and a method of using the same, so as to solve the problem that the prior art cannot achieve rapid response.

[0010] According to a first aspect of an embodiment of the present disclosure, a software-based satellite two-way time comparison modulation system is provided, the system comprising:

[0011] The main control module is used to control the configuration information initialization module, the SDR device initialization module, the baseband signal generation module, the signal data bit generation module and the signal transmission module, and control the information interaction and communication between the modules;

[0012] Configuration information initialization module, used to obtain SDR device initialization parameters and baseband signal initialization parameters;

[0013] The SDR device initialization module is used to obtain the SDR device initialization parameters and complete the initialization settings of the SDR device according to the 10MHz signal, 1PPS signal and the SDR device initialization parameters;

[0014] A baseband signal generation module, used to generate target baseband data according to the baseband signal initialization parameters, and put the target baseband data into the global memory; wherein the target baseband data includes Time-Tag PRN code baseband data and data bit PRN code baseband data;

[0015] A signal data bit generation module is used to generate Time-Tag data and signal data bits, and put the first signal data bit into the data bit message queue according to the sequence; wherein the data bit information of the Time-Tag data is consistent with the data bit information of the Time-Tag PRN code baseband data, and the signal data bit is consistent with the data bit information of the data bit PRN code baseband data;

[0016] The signal transmission module is used to obtain the corresponding data bit information from the data bit message queue in sequence, obtain the corresponding target baseband data from the global memory according to the data bit information, and send the obtained target baseband data to the SDR device.

[0017] Furthermore, the SDR device initialization module includes:

[0018] The first device initialization submodule is used to set the SDR device position, frequency reference signal source, 1PPS signal source, sampling rate, data bit number, carrier frequency, signal gain and filter bandwidth according to the SDR device initialization parameters;

[0019] The second device initialization submodule is used to set the local clock of the SDR device according to the 10MHz signal and the 1PPS signal, and specify the start time of signal transmission.

[0020] Furthermore, the baseband signal generation module includes:

[0021] The spread spectrum code generation submodule is used to generate a corresponding spread spectrum code according to the PRN code and PRN code length in the baseband signal initialization parameters;

[0022] The PRN baseband data generation submodule is used to interpolate, offset and flip the spread spectrum code according to the code rate and the SDR device sampling rate to generate data bit PRN code baseband data and Time-Tag PRN code baseband data;

[0023] The filtering submodule is used to filter the data bit PRN code baseband data and the Time-Tag PRN code baseband data to obtain the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data; and obtain the target baseband data according to the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data;

[0024] The storage submodule is used to put the target baseband data into the global memory.

[0025] Further, filtering the data bit PRN code baseband data and the Time-Tag PRN code baseband data includes:

[0026] Perform Fourier transform FFT on the data bit PRN code baseband data and the Time-Tag PRN code baseband data of one code period to obtain frequency domain data of the data bit PRN code baseband data and the Time-Tag PRN code baseband data;

[0027] Set the out-of-band value to 0 according to the filter bandwidth and frequency resolution;

[0028] Perform inverse Fourier transform IFFT on the frequency domain data of the data bit PRN code baseband data and the frequency domain data of the time-tag PRN code baseband data to obtain filtered data bit PRN code baseband data and filtered time-tag PRN code baseband data;

[0029] The target baseband data is obtained according to the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data.

[0030] Furthermore, all PRN baseband data are converted into a preset data type according to the corresponding data bit number and signal amplitude of the SDR device.

[0031] Furthermore, the signal transmission module also includes:

[0032] The time comparison submodule is used to align the sending time of the corresponding PRN baseband data with the rising edge of the 1PPS signal of the SDR device when the Time-Tag data is detected.

[0033] According to a second aspect of an embodiment of the present disclosure, a method for using a software-based satellite two-way time comparison modulation system is provided, the method comprising:

[0034] The SDR device initialization module obtains the SDR device initialization parameters sent by the configuration information initialization module, and completes the initialization settings of the SDR device in combination with the 10MHz signal and the 1PPS signal;

[0035] The baseband signal generation module generates all Time-Tag PRN code baseband data and data bit PRN code baseband data in advance;

[0036] The baseband signal generation module performs filtering processing on the Time-Tag PRN code baseband data and the data bit PRN code baseband data to obtain the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data, and obtains the target baseband data, and puts the target baseband data into the global memory;

[0037] The signal data bit generation module generates the Time-Tag data and the signal data bit in real time, and sends the Time-Tag data and the signal data bit to the data bit message queue in sequence;

[0038] The signal transmission module sequentially obtains the Time-Tag data and the signal data bit in the data bit message queue, and obtains the corresponding target baseband data from the global memory according to the Time-Tag data and the signal data bit;

[0039] The signal transmission module transmits the acquired target baseband data to the SDR device in sequence.

[0040] Furthermore, the method further comprises:

[0041] The SDR device performs up-conversion operation on the target baseband data according to the configuration to obtain a data intermediate frequency signal;

[0042] Send the data IF signal to external devices.

[0043] Further, the signal transmission module sequentially obtains the Time-Tag data and the signal data bit in the data bit message queue, and obtains the corresponding target baseband data from the global memory according to the Time-Tag data and the signal data bit, including:

[0044] Verify whether the current time has changed from the last sent time. If the seconds have changed, generate the Time-Tag data and signal data bits in real time, and send the Time-Tag data and signal data bits to the data bit message queue in sequence;

[0045] Obtain the Time-Tag data and signal data bits in the data bit message queue in order, and obtain the corresponding target baseband data from the global memory according to the Time-Tag data and signal data bits;

[0046] Determine the data type of the acquired target baseband data. If it is a Time-Tag type, set the transmission time of the target baseband data to align with the next rising edge of the 1PPS signal.

[0047] The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects:

[0048] In the embodiments of the present disclosure, through the above-mentioned software-based satellite two-way time comparison modulation system and its use method, the loose coupling design between the modules can quickly realize the generation of satellite two-way time comparison signals with different precisions, different frequencies, different modulation modes and different coding modes. While ensuring the measurement accuracy and stability, the satellite two-way time comparison modulation system is made flexible and universal, realizing the rapid migration between scientific experiments and practical applications. And it can overcome the problems of high design difficulty, long design cycle and poor flexibility of analog equipment and FPGA-based equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0050] Figure 1 A schematic diagram showing a software-based satellite two-way time comparison modulation system in an exemplary embodiment of the present disclosure is shown;

[0051] Figure 2 A schematic diagram showing the device structure of a software-based satellite two-way time comparison modulation system in an exemplary embodiment of the present disclosure is shown;

[0052] Figure 3 A step diagram showing a method for using a software-based satellite two-way time comparison modulation system in an exemplary embodiment of the present disclosure;

[0053] Figure 4 An activity diagram showing a system initialization phase in an exemplary embodiment of the present disclosure;

[0054] Figure 5 An activity diagram of the signal transmission phase in an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0055] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0056] In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0057] In this example implementation, a software-based satellite two-way time comparison modulation system is first provided. Figure 1 As shown in , the software-based satellite two-way time comparison modulation system may include: a main control module, a configuration information initialization module, an SDR device initialization module, a baseband signal generation module, a signal data bit generation module, and a signal transmission module.

[0058] The main control module is used to control the configuration information initialization module, the SDR device initialization module, the baseband signal generation module, the signal data bit generation module and the signal transmission module, and control the information interaction and communication between the modules;

[0059] Configuration information initialization module, used to obtain SDR device initialization parameters and baseband signal initialization parameters;

[0060] The SDR device initialization module is used to obtain the SDR device initialization parameters and complete the initialization settings of the SDR device according to the 10MHz signal, 1PPS signal and the SDR device initialization parameters;

[0061] A baseband signal generation module, used to generate target baseband data according to the baseband signal initialization parameters, and put the target baseband data into the global memory; wherein the target baseband data includes Time-Tag PRN code baseband data and data bit PRN code baseband data;

[0062] A signal data bit generation module is used to generate Time-Tag data and signal data bits, and put the first signal data bit into the data bit message queue according to the sequence; wherein the data bit information of the Time-Tag data is consistent with the data bit information of the Time-Tag PRN code baseband data, and the signal data bit is consistent with the data bit information of the data bit PRN code baseband data;

[0063] The signal transmission module is used to obtain the corresponding data bit information from the data bit message queue in sequence, obtain the corresponding target baseband data from the global memory according to the data bit information, and send the obtained target baseband data to the SDR device.

[0064] Through the above-mentioned software-based satellite two-way time comparison modulation system, the loose coupling design between the modules can quickly realize the generation of satellite two-way time comparison signals with different precision, different frequencies, different modulation methods and different coding modes. While ensuring the measurement accuracy and stability, the satellite two-way time comparison modulation system is made flexible and universal, realizing the rapid migration between scientific experiments and practical applications. It can also overcome the problems of high design difficulty, long design cycle and poor flexibility of analog equipment and FPGA-based equipment.

[0065] Next, we will refer to Figure 1 to Figure 2 The various components of the above-described software-based satellite two-way time ratio modulation system in this example embodiment are described in more detail.

[0066] In one embodiment, the main control module is used to control the startup of the configuration information initialization module, the SDR device initialization module, the baseband signal generation module, the signal data bit generation module, and the signal transmission module, and also controls the information interaction and communication between the modules.

[0067] The configuration information initialization module is used to obtain the initialization information of the SDR device in the system (and the SDR device initialization parameters) and the baseband signal parameter initialization information (i.e., the baseband signal initialization parameters).

[0068] The SDR device initialization module sets the SDR device position, frequency reference signal source, 1PPS signal source, sampling rate, data bit number, carrier frequency, signal gain, and filter bandwidth according to the initialization information of the SDR device. After the above basic information is set, the local clock of the SDR device is set according to the synchronized 1PPS signal. Considering that the accuracy of the comparison directly depends on the alignment degree of the signal start position and the 1PPS rising edge, it is necessary to specify the start time of the signal transmission.

[0069] The baseband signal generation module generates a baseband signal that meets the sampling rate and data bit number required by the SDR device according to the initialization information. The specific process is as follows:

[0070] 1. Generate the corresponding spread spectrum code according to the PRN code and PRN code length.

[0071] 2. After interpolating the spread spectrum code according to the code rate and the sampling rate of the SDR device and performing operations such as offset and flipping, a PRN code that can represent data bits such as 0 and 1 (i.e., data bit PRN code baseband data) and Time-Tag flag bits (i.e., Time-Tag PRN code baseband data) is generated, and these PRN codes are numbered (for example, the spread spectrum code representing the data bit 0 is numbered as -1, and the spread spectrum code representing the data bit 1 is numbered as 1) and placed in the global memory.

[0072] 3. Considering the requirements for transmission bandwidth in TWSTFT comparison and the influence of oversampling caused by interpolation operation, it is necessary to filter the generated PRN code: first, perform Fourier transform FFT on the data bit PRN code baseband data and Time-Tag PRN code baseband data of one code period to obtain the frequency domain data of the data bit PRN code baseband data and the Time-Tag PRN code baseband data; then set the out-of-band value to 0 according to the filtering bandwidth and frequency resolution; finally, perform inverse Fourier transform IFFT on the frequency domain data of the data bit PRN code baseband data and the frequency domain data of the Time-Tag PRN code baseband data to obtain the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data; obtain the target baseband data according to the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data.

[0073] 4. Convert all PRN baseband data to the specified data type (float, char or short) according to the corresponding data bit number and signal amplitude of the SDR device.

[0074] The signal data bit generation module is used to generate Time-Tag data and signal data bits (the data bit information of Time-Tag data is consistent with that of Time-Tag PRN code baseband data, and the data bit information of signal data bits is consistent with that of data bit PRN code baseband data), and put the signal data bits into the data bit message queue according to the sequence.

[0075] The signal transmission module is used to obtain the corresponding data bit information (i.e., PRN number) from the data bit message queue in order, obtain the corresponding PRN baseband data from the global memory according to the code, and send the obtained PRN baseband data to the SDR device. Considering the requirements for signal time accuracy, when the Time-Tag value is detected, the transmission time of the corresponding PRN baseband data should be aligned with the rising edge of the 1PPS signal of the SDR device.

[0076] In a specific embodiment, Figure 2 As shown, the operating hardware environment of the software-based satellite two-way time comparison modulation system of the present application includes: software defined radio equipment (SDR), industrial computer / server and computing card (GPU).

[0077] The software defined radio (SDR) converts the baseband signal sent by the industrial computer / server to a digital intermediate frequency according to the initialization parameters and the received external frequency reference signal, and performs filtering and power amplification operations according to the configuration parameters. After digital-to-analog conversion, the specified Time-Tag data is aligned with the external clock signal and the required analog signal is output. The external frequency reference signal is a 10MHz signal, and the external clock signal is a 1PPS signal.

[0078] The industrial computer / server is used to run the system and is responsible for the control and data exchange of the software-defined radio device (SDR) and the computing card (GPU).

[0079] The computing card (GPU) implements the filtering operation of the Time-Tag and the information data bits corresponding to the PRN code baseband data through parallel algorithms.

[0080] This example implementation also provides a method for using a software-based satellite two-way time comparison modulation system. Figure 3 As shown in , the method for using the software-based satellite two-way time comparison modulation system may include: steps S201 to S206.

[0081] Step S201: The SDR device initialization module obtains the SDR device initialization parameters sent by the configuration information initialization module, and completes the initialization settings of the SDR device in combination with the 10MHz signal and the 1PPS signal;

[0082] Step S202: The baseband signal generation module generates all Time-Tag PRN code baseband data and data bit PRN code baseband data in advance;

[0083] Step S203: the baseband signal generation module performs filtering processing on the Time-Tag PRN code baseband data and the data bit PRN code baseband data to obtain filtered data bit PRN code baseband data and filtered Time-Tag PRN code baseband data, and obtains target baseband data, and puts the target baseband data into the global memory;

[0084] Step S204: the signal data bit generation module generates the Time-Tag data and the signal data bit in real time, and sends the Time-Tag data and the signal data bit to the data bit message queue in sequence;

[0085] Step S205: the signal transmission module sequentially obtains the Time-Tag data and the signal data bits in the data bit message queue, and obtains the corresponding target baseband data from the global memory according to the Time-Tag data and the signal data bits;

[0086] Step S206: The signal transmission module transmits the acquired target baseband data to the SDR device in sequence.

[0087] In one embodiment, the SDR device performs an up-conversion operation on the target baseband data according to the configuration to obtain a data intermediate frequency signal;

[0088] Send the data IF signal to external devices.

[0089] In one embodiment, the signal transmission module sequentially obtains the time-tag data and the signal data bit in the data bit message queue, and the step of obtaining the corresponding target baseband data from the global memory according to the time-tag data and the signal data bit includes:

[0090] Verify whether the current time has changed from the last sent time. If the seconds have changed, generate the Time-Tag data and signal data bits in real time, and send the Time-Tag data and signal data bits to the data bit message queue in sequence;

[0091] Obtain the Time-Tag data and signal data bits in the data bit message queue in order, and obtain the corresponding target baseband data from the global memory according to the Time-Tag data and signal data bits;

[0092] Determine the data type of the acquired target baseband data. If it is a Time-Tag type, set the transmission time of the target baseband data to align with the next rising edge of the 1PPS signal.

[0093] In one embodiment, a method for using a software-based satellite two-way time comparison modulation system includes two parts: system initialization and signal transmission.

[0094] like Figure 4 As shown, the system initialization phase includes the following steps:

[0095] Read system initialization configuration information from the configuration file;

[0096] Set the sampling rate, sampling data type, frequency reference signal source, 1PPS signal source, data bit, carrier frequency, signal gain, and filter bandwidth of the SDR device during operation, and complete the setting of the SDR device clock, frequency reference signal lock verification, and signal transmission start time.

[0097] Generate corresponding spreading code according to local PRN code and code length;

[0098] The spread spectrum code is interpolated and offset and flipped according to the code rate and the sampling rate of the SDR device, and a PRN code that can represent data bits such as 0 and 1 and the Time-Tag flag bit in a code period is generated;

[0099] Perform Fourier transform FFT on all the above PRN codes to obtain the frequency domain data of the PRN code, then set the out-of-band value of the PRN code frequency domain data to 0 according to the filter bandwidth and frequency resolution, and finally perform inverse Fourier transform IFFT on the frequency domain data of the PRN code to obtain the filtered PRN baseband data;

[0100] According to the corresponding data bit number and signal amplitude of the SDR device, all PRN baseband data are converted to the specified data type (float, char or short), and then these PRN code baseband data are numbered (for example, the spread spectrum code representing 0 data bit is numbered as -1, and the spread spectrum code representing 1 data bit is numbered as 1) and placed in the global memory.

[0101] like Figure 5 As shown, the sending phase includes the following steps:

[0102] Verify whether the current time has changed from the last sent time. If a second change occurs, generate Time-Tag data and signal data bits in real time and send these data sequentially to the data bit message queue;

[0103] Obtain the Time-Tag data and signal data bits in the data bit message queue in order, and obtain the corresponding PRN code baseband data from the global memory based on these data;

[0104] Determine the type of data obtained; if it is a Time-Tag type, set the data transmission time to align with the next 1PPS signal rising edge, and then send the corresponding PRN code baseband data to the SDR device; if it is not a Time-Tag type, send the corresponding PRN code baseband data to the SDR device.

[0105] Through the software-based satellite two-way time comparison modulation system and its use method, the loose coupling design between the modules can quickly realize the generation of satellite two-way time comparison signals with different precision, different frequencies, different modulation methods and different coding modes, without the need for hardware design and FPGA design-related knowledge. While ensuring the measurement accuracy and stability, the satellite two-way time comparison modulation system is made flexible and universal, realizing the rapid migration between scientific experiments and practical applications. It can also overcome the problems of high design difficulty, long design cycle and poor flexibility of analog equipment and FPGA-based equipment.

[0106] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0107] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A software-based satellite two-way time comparison modulation system, characterized in that: The system includes: The main control module is used to control the configuration information initialization module, the SDR device initialization module, the baseband signal generation module, the signal data bit generation module and the signal transmission module, and control the information interaction and communication between the modules; Configuration information initialization module, used to obtain SDR device initialization parameters and baseband signal initialization parameters; The SDR device initialization module is used to obtain the SDR device initialization parameters and complete the initialization settings of the SDR device according to the 10MHz signal, 1PPS signal and the SDR device initialization parameters; A baseband signal generation module, used to generate target baseband data according to the baseband signal initialization parameters, and put the target baseband data into the global memory; wherein the target baseband data includes Time-Tag PRN code baseband data and data bit PRN code baseband data; A signal data bit generation module is used to generate Time-Tag data and signal data bits, and put the first signal data bit into the data bit message queue according to the sequence; wherein the data bit information of the Time-Tag data is consistent with the data bit information of the Time-Tag PRN code baseband data, and the signal data bit is consistent with the data bit information of the data bit PRN code baseband data; The signal transmission module is used to obtain the corresponding data bit information from the data bit message queue in sequence, obtain the corresponding target baseband data from the global memory according to the data bit information, and send the obtained target baseband data to the SDR device.

2. The software-based satellite two-way time comparison modulation system according to claim 1, characterized in that: The SDR device initialization module includes: The first device initialization submodule is used to set the SDR device position, frequency reference signal source, 1PPS signal source, sampling rate, data bit number, carrier frequency, signal gain and filter bandwidth according to the SDR device initialization parameters; The second device initialization submodule is used to set the local clock of the SDR device according to the 10MHz signal and the 1PPS signal, and specify the start time of signal transmission.

3. The software-based satellite two-way time comparison modulation system according to claim 1, characterized in that: The baseband signal generation module includes: The spread spectrum code generation submodule is used to generate a corresponding spread spectrum code according to the PRN code and PRN code length in the baseband signal initialization parameters; The PRN baseband data generation submodule is used to interpolate, offset and flip the spread spectrum code according to the code rate and the SDR device sampling rate to generate data bit PRN code baseband data and Time-Tag PRN code baseband data; The filtering submodule is used to filter the data bit PRN code baseband data and the Time-Tag PRN code baseband data to obtain the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data; and obtain the target baseband data according to the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data; The storage submodule is used to put the target baseband data into the global memory.

4. The software-based satellite two-way time comparison modulation system according to claim 3, characterized in that: The filtering process for the data bit PRN code baseband data and the Time-Tag PRN code baseband data includes: Perform Fourier transform FFT on the data bit PRN code baseband data and the Time-Tag PRN code baseband data of one code period to obtain frequency domain data of the data bit PRN code baseband data and the Time-Tag PRN code baseband data; Set the out-of-band value to 0 according to the filter bandwidth and frequency resolution; Perform inverse Fourier transform IFFT on the frequency domain data of the data bit PRN code baseband data and the frequency domain data of the time-tag PRN code baseband data to obtain filtered data bit PRN code baseband data and filtered time-tag PRN code baseband data; The target baseband data is obtained according to the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data.

5. The software-based satellite two-way time comparison modulation system according to claim 4, characterized in that: Convert all PRN baseband data into preset data types according to the corresponding data bit number and signal amplitude of the SDR device.

6. The software-based satellite two-way time comparison modulation system according to claim 1, characterized in that: The signal transmission module also includes: The time comparison submodule is used to align the sending time of the corresponding PRN baseband data with the rising edge of the 1PPS signal of the SDR device when the Time-Tag data is detected.

7. A method for using a software-based satellite two-way time comparison modulation system, characterized in that: The method includes: The SDR device initialization module obtains the SDR device initialization parameters sent by the configuration information initialization module, and completes the initialization settings of the SDR device in combination with the 10MHz signal and the 1PPS signal; The baseband signal generation module generates all Time-Tag PRN code baseband data and data bit PRN code baseband data in advance; The baseband signal generation module performs filtering processing on the Time-Tag PRN code baseband data and the data bit PRN code baseband data to obtain the filtered data bit PRN code baseband data and the filtered Time-Tag PRN code baseband data, and obtains the target baseband data, and puts the target baseband data into the global memory; The signal data bit generation module generates the Time-Tag data and the signal data bit in real time, and sends the Time-Tag data and the signal data bit to the data bit message queue in sequence; The signal transmission module sequentially obtains the Time-Tag data and the signal data bit in the data bit message queue, and obtains the corresponding target baseband data from the global memory according to the Time-Tag data and the signal data bit; The signal transmission module transmits the acquired target baseband data to the SDR device in sequence.

8. The method for using the software-based satellite two-way time comparison modulation system according to claim 7, characterized in that: The method further includes: The SDR device performs up-conversion operation on the target baseband data according to the configuration to obtain a data intermediate frequency signal; Send the data intermediate frequency signal to the external device.

9. The method for using the software-based satellite two-way time comparison modulation system according to claim 7, characterized in that: The signal transmission module sequentially obtains the time-tag data and the signal data bit in the data bit message queue, and obtains the corresponding target baseband data from the global memory according to the time-tag data and the signal data bit, including: Verify whether the current time has changed from the last sent time. If the seconds have changed, generate the Time-Tag data and signal data bits in real time, and send the Time-Tag data and signal data bits to the data bit message queue in sequence; Obtain the Time-Tag data and signal data bits in the data bit message queue in order, and obtain the corresponding target baseband data from the global memory according to the Time-Tag data and signal data bits; Determine the data type of the acquired target baseband data. If it is a Time-Tag type, set the transmission time of the target baseband data to align with the next rising edge of the 1PPS signal.

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