Beidou B1I signal pseudo-range simulation method based on time synchronization

Abstract

The invention discloses a Beidou B1I signal pseudo-range simulation method based on time synchronization, which relates to the technical field of satellite navigation, and realizes time synchronization initialization by initializing effective signal triggering, loading initial parameters, detecting a rising edge of a time reference source, starting delay counting and automatically activating signal enabling when an alignment delay threshold value is reached; the C / A code time sequence precision and the dynamic adaptability are guaranteed through two time sequence control, the precision of the pseudo-range calculated based on the C / A code is guaranteed by calculating the convergence pseudo-range, and the pseudo-range dynamic generation is realized; and finally, the analog C / A code and the navigation message are modulated to a carrier after being subjected to XOR, analog satellite signals are generated through digital-to-analog conversion, and signal modulation and output are achieved. According to the invention, navigation signals completely consistent with real signals can be provided in an environment without real satellite signals, the blank in the prior art is filled, and the reliability and applicability of a positioning system are improved.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation technology, and in particular to a pseudorange simulation method for BeiDou B1I signals based on time synchronization. Background Technology

[0002] In satellite navigation systems, receivers rely on navigation signals (such as the BeiDou B1I signal) transmitted by satellites for positioning. However, in environments without satellite signal coverage, such as indoors, tunnels, and underground, traditional receivers cannot perform positioning correctly, causing navigation functionality to fail. Common solutions currently include: Inertial navigation (INS) assisted positioning: relies on sensors such as accelerometers and gyroscopes, but suffers from cumulative errors, leading to decreased accuracy over long-term use. Pseudolite technology: deploys ground-based base stations that simulate satellite signals, but is costly and struggles to achieve seamless switching with real satellite signals. Wireless communication network-assisted positioning (e.g., 5G, WiFi): depends on external infrastructure and is unusable in remote areas or areas without network coverage.

[0003] However, existing technologies all have the following common drawbacks: they cannot fully simulate real satellite signals, which makes it impossible for the receiver to correctly interpret pseudorange information, resulting in low positioning accuracy; the time synchronization accuracy is insufficient, and there is a deviation between the simulated signal and the real satellite, which affects the receiver's time synchronization and positioning functions; and the compatibility is poor, with some solutions only applicable to specific receivers and difficult to adapt to general GNSS equipment on the market. Summary of the Invention

[0004] In view of this, this application provides a pseudorange simulation method for BeiDou B1I signals based on time synchronization to address the shortcomings of existing technologies.

[0005] The first aspect of this application provides a pseudorange simulation method for BeiDou B1I signals based on time synchronization, including: When initialization valid signal Upon triggering, the hardware loads the code issued by the SDK, including the initial frequency of the NCO and the initial phase of the G1 / G2 shift registers. The hardware detects the rising edge of the external time reference source and starts a delay counter. When the delay counter counts to reach the alignment delay threshold issued by the SDK, the hardware automatically activates signal generation enable. The hardware reset of the G1 / G2 shift register is triggered every 1ms, and the hardware receives the NCO frequency control word and carrier NCO frequency control word sent by the SDK every 1s, which together constitute the timing control algorithm. The real-time pseudorange is calculated using the following formula. The difference between the real-time pseudorange and the theoretical pseudorange is fed back to the SDK. Based on the difference, the damping factor parameter is dynamically adjusted to ensure that the real-time pseudorange calculation converges, and the converged pseudorange is obtained. This is the pseudorange distance deviation correction amount. The cumulative residual value of the code NCO; An initial C / A code is obtained by performing an XOR operation between the G1 shift register and the G2 shift register. The initial C / A code is then verified and adjusted using the timing control algorithm and the convergence pseudorange to obtain an analog C / A code. After performing an XOR operation between the analog C / A code and the navigation message, the signal is modulated onto the carrier wave and output as 8-bit IQ data to a digital-to-analog converter for digital-to-analog conversion, generating a BeiDou B1I radio frequency signal, which is an analog satellite signal.

[0006] In one possible implementation of the first aspect, the pseudorange distance deviation correction amount is obtained. include: The remaining chip count and current milliseconds are obtained in real time through an internal hardware counter and fed back to the SDK. Based on the remaining number of chips and the current number of milliseconds, and using the SDK algorithm, the pseudorange distance deviation correction amount is obtained. and accuracy adaptation parameters The accuracy adaptation parameters Used to process the pseudorange distance deviation correction amount The accuracy deviation.

[0007] In one possible implementation of the first aspect, the SDK-issued NCO frequency control word and the carrier NCO frequency control word include: Based on the pseudorange distance deviation correction amount By reverse calculation, the chip transmission time deviation and Doppler frequency shift can be obtained; The chip transmission time deviation is converted into a recognizable NCO frequency control word, and the Doppler frequency shift is converted into a recognizable carrier NCO frequency control word.

[0008] In one possible implementation of the first aspect, triggering a hardware reset of the G1 / G2 shift registers every 1ms includes: The C / A code of Beidou B1I has a complete chip cycle of 1ms. Every 1ms, the hardware reset of the G1 / G2 shift register is triggered, so that the corresponding shift register starts generating chips again from the initial phase.

[0009] In one possible implementation of the first aspect, the NCO frequency control word and carrier NCO frequency control word triggered every 1 second by the hardware receiving SDK include: The NCO frequency is adjusted by the NCO frequency control word to compensate for changes in chip transmission time, so that the simulated C / A code is consistent with the arrival time of the real satellite signal. If the satellite is far from the receiver, the chip transmission time becomes longer, the NCO frequency control word of the code increases, and the NCO frequency of the code is adjusted to increase. If the satellite is close to the receiver, the chip transmission time becomes shorter, the NCO frequency control word of the code decreases, and the NCO frequency of the code is adjusted to decrease.

[0010] In one possible implementation of the first aspect, the NCO frequency control word and carrier NCO frequency control word triggered every 1 second by the hardware receiving SDK further include: The carrier NCO frequency is adjusted by the carrier NCO frequency control word to compensate for the Doppler frequency shift, so that the frequency shift characteristics of the analog carrier are consistent with the real satellite signal. If the satellite is close to the receiver, the carrier NCO frequency control word is increased, and the carrier NCO frequency is adjusted to rise. If the satellite moves away from the receiver, the carrier NCO frequency control word decreases, and the carrier NCO frequency is adjusted to decrease.

[0011] In one possible implementation of the first aspect, the navigation message is cached via FIFO, and satellite ephemeris and clock parameters are dynamically injected.

[0012] In one possible implementation of the first aspect, through The module performs calculations of real-time pseudorange and convergence.

[0013] In one possible implementation of the first aspect, the external time reference source employs a 1PPS second pulse.

[0014] In one possible implementation of the first aspect, the hardware is an FPGA module.

[0015] Its beneficial effects are as follows: This invention discloses a pseudorange simulation method for BeiDou B1I signals based on time synchronization, aiming to solve the problem of positioning failure of traditional GNSS receivers in environments without satellite signals, such as indoors and tunnels. It initializes a valid signal trigger, loads initial parameters, and starts delay counting by detecting the rising edge of the time reference source. When the alignment delay threshold is reached, signal enable is automatically activated, achieving time synchronization initialization. Two timing controls ensure the timing accuracy and dynamic adaptability of the C / A code. By calculating the convergent pseudorange, the accuracy of the pseudorange calculated based on the C / A code is ensured, achieving dynamic pseudorange generation. Finally, by XORing the simulated C / A code with the navigation message and modulating it onto the carrier, and through digital-to-analog conversion, a simulated satellite signal is generated, achieving signal modulation and output. This invention can provide navigation signals completely consistent with real signals in environments without real satellite signals, filling the gap in existing technology and improving the reliability and applicability of positioning systems. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a pseudorange simulation method for BeiDou B1I signals based on time synchronization, provided in an embodiment of this application. Detailed Implementation

[0018] 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 some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0020] Example In existing technologies, traditional receivers cannot perform positioning correctly in environments without satellite signal coverage, such as indoors, tunnels, and underground, leading to navigation failure. Common solutions include inertial navigation (INS)-assisted positioning, pseudosatellite technology, and wireless communication network-assisted positioning (such as 5G and WiFi). However, these solutions all share the following drawbacks: they cannot fully simulate real satellite signals, causing the receiver to fail to correctly interpret pseudorange information, resulting in low positioning accuracy; time synchronization accuracy is insufficient, with deviations between simulated signals and real satellite signals affecting the receiver's timing and positioning functions; and compatibility is poor, with some solutions only applicable to specific receivers and difficult to adapt to general-purpose GNSS equipment on the market.

[0021] Therefore, this application provides a pseudorange simulation method for BeiDou B1I signals based on time synchronization, such as... Figure 1 As shown, it includes: When initialization valid signal Upon triggering, the hardware loads the code issued by the SDK, including the initial frequency of the NCO and the initial phase of the G1 / G2 shift registers. The hardware detects the rising edge of the external time reference source and starts a delay counter. When the delay counter counts to reach the alignment delay threshold issued by the SDK, the hardware automatically activates signal generation enable. The hardware reset of the G1 / G2 shift register is triggered every 1ms, and the hardware receives the NCO frequency control word and carrier NCO frequency control word sent by the SDK every 1s, which together constitute the timing control algorithm. The real-time pseudorange is calculated using the following formula. The difference between the real-time pseudorange and the theoretical pseudorange is fed back to the SDK. Based on the difference, the damping factor parameter is dynamically adjusted to ensure that the real-time pseudorange calculation converges, and the converged pseudorange is obtained. This is the pseudorange distance deviation correction amount. The cumulative residual value of the code NCO; An initial C / A code is obtained by performing an XOR operation between the G1 shift register and the G2 shift register. The initial C / A code is then verified and adjusted using the timing control algorithm and the convergence pseudorange to obtain an analog C / A code. After performing an XOR operation between the analog C / A code and the navigation message, the signal is modulated onto the carrier wave and output as 8-bit IQ data to a digital-to-analog converter for digital-to-analog conversion, generating a BeiDou B1I radio frequency signal, which is an analog satellite signal.

[0022] This embodiment provides a pseudorange simulation method for BeiDou B1I signals based on time synchronization, which mainly includes three steps: time synchronization initialization, pseudorange dynamic generation, and signal modulation and output. Specifically: Step 1: Time synchronization initialization Initialization trigger, when the initialization is valid signal When valid, load the initial parameter code, NCO initial frequency, and G1 / G2 shift register initial phase to complete startup preparation; Synchronous control detects the rising edge of an external 1PPS second pulse, starts a delay counter, and when the counter value reaches the alignment delay threshold, the excitation signal generation enable (work=1) is activated, completing the time base alignment.

[0023] Step 2: Dynamic generation of pseudorange Timing control: The G1 / G2 shift register is reset every 1ms to update the C / A code phase, ensuring millisecond-level timing matching between the generated chip and the real satellite signal; every 1s, the pseudorange change caused by satellite motion is simulated according to the code NCO frequency control word and carrier NCO frequency control word issued by the SDK. Pseudorange calculation, through Module execution core formula Furthermore, based on the residual calculated from the pseudorange, the damping factor is dynamically adjusted to ensure the convergence speed and accuracy of the pseudorange calculation.

[0024] Step 3: Signal Modulation and Output The final generated analog C / A code is XORed with the navigation message and then modulated onto the carrier wave to generate 8-bit IQ data. The signal is sent to the DAC (digital-to-analog converter) and finally generates the BeiDou B1I radio frequency signal, which is an analog satellite signal.

[0025] In this embodiment, high-speed chip generation and carrier modulation are mainly achieved through hardware FPGA, and pseudorange distance deviation correction and accuracy adaptation parameters are dynamically calculated using SDK. Specifically: FPGA implementation of high-speed chip generation: C / A codes are generated by performing an XOR operation using the G1 / G2 shift registers to ensure that the chip structure is completely consistent with the actual satellite signal. Precise chip generation rhythm is achieved through built-in timing control. Key control logic includes: resetting the G1 / G2 shift register every 1ms to avoid cumulative chip phase offset and ensure that the chip sequence every millisecond is completely synchronized with the timing of the real satellite signal, further ensuring the accuracy of pseudorange resolution; setting a chip counter to count chips, with a counting range of 0~2045, corresponding to the standard rate of "2046 chips / millisecond" of BeiDou B1I signal, generating 1 chip for each count, and hardware-level counting ensures high speed and zero delay.

[0026] FPGA implementation of carrier modulation: The carrier signal is generated through a numerically controlled oscillator (NCO) hardware architecture and supports dynamic frequency adjustment to simulate the carrier characteristics of real satellite signals. The dynamic frequency adjustment involves receiving and updating the carrier frequency correction value (code NCO frequency control word and carrier NCO frequency control word) issued by the SDK every 1 second, thereby changing the frequency of the carrier signal so that the frequency offset of the simulated carrier and the real satellite signal caused by relative motion is completely consistent, ensuring that the receiver can correctly resolve the Doppler component in the pseudorange.

[0027] SDK dynamically calculates pseudorange distance deviation correction and accuracy adaptation parameters: The pseudorange distance deviation correction is calculated based on the number of remaining pseudo chips and the current number of milliseconds, derived using the SDK algorithm. Essentially, it reflects the dynamic changes in pseudorange through two real-time variables: the number of remaining chips reflects the chip deviation within the current millisecond, and the current number of milliseconds reflects the timing deviation across milliseconds. The SDK algorithm transforms the "remaining chip deviation" and "timing deviation" into a unified pseudorange distance deviation correction, which is directly applied in the FPGA. The module's pseudorange calculation ensures that the pseudorange calculation takes into account real-time signal propagation deviations; The accuracy adaptation parameter is the accuracy deviation calculated after processing the pseudorange distance deviation correction, ensuring that the parameter is compatible with the hardware operation accuracy of the FPGA. (Module bit-width operation requirements).

[0028] In this example, the dynamic generation of pseudorange needs to simulate pseudorange changes caused by satellite motion (such as Doppler shift and pseudorange transmission time changes). These two changes directly correspond to the adjustment requirements of the C / A code frequency and the carrier frequency. Therefore, the core basis for the SDK to calculate the NCO frequency control word and the carrier NCO frequency control word is: The calculation of the code NCO frequency control word is based on the changes in C / A code transmission time caused by satellite motion. The relative motion between the satellite and the receiver will cause a slight deviation in the chip transmission time of the C / A code to the receiver. This deviation needs to be simulated by adjusting the generation frequency of the C / A code. The code NCO frequency control word is the code NCO frequency adjustment value calculated by the SDK based on the chip transmission time deviation. The basis for the carrier NCO frequency control word: Doppler frequency shift caused by satellite motion. The relative motion between the satellite and the receiver will cause a frequency shift in the carrier signal (Doppler effect). This frequency shift directly affects pseudorange resolution. Therefore, the SDK needs to calculate the carrier NCO frequency control word based on the Doppler frequency shift to adjust the output frequency of the carrier NCO and compensate for the frequency shift deviation.

[0029] The calculation of the NCO frequency control word and the carrier NCO frequency control word is as follows: First, the pseudorange distance deviation correction is calculated using the remaining number of chips and the current number of milliseconds. Then, the chip transmission time deviation and Doppler offset are derived from the pseudorange distance deviation correction. These two physical quantities are then converted into a frequency control word that the NCO can recognize. Finally, the SDK sends the calculated frequency control word to the FPGA to complete the NCO frequency update.

[0030] The real-time pseudorange calculation formula in this embodiment Its construction logic is as follows: the pseudorange distance deviation correction amount is calculated using the remaining chip count and milliseconds (which is also a parameter for dynamically adjusting the damping factor based on the residual). Its function is to compensate for the pseudorange deviation caused by satellite motion and signal propagation, and to adjust the accuracy extension coefficient. The bit width range is increased to be compatible with FPGA hardware operations to avoid loss of operational precision due to excessively small values, and to ensure that the hardware implementation accuracy of pseudorange calculation meets the requirements of nanosecond-level time synchronization. The accumulated residual value of the NCO code is used to compensate for the small precision errors generated by the NCO during frequency adjustment, thereby further improving the accuracy of the final real-time pseudorange value.

[0031] The purpose of setting up a dual-timing control core in this embodiment is to match the characteristics of the C / A code and the satellite motion characteristics respectively, so as to ensure the authenticity of the pseudorange simulation. The specific basis is as follows: the C / A code phase is updated every 1ms. The C / A code rate of the Beidou B1I signal is 1.023MHz, and 2046 chips are generated every millisecond. The G1 / G2 shift register is reset every 1ms, which can accurately match the generation rhythm of the real C / A code and avoid pseudorange errors caused by code phase offset. The NCO frequency is updated every 1s. The satellite motion period is about 11 hours and 58 minutes. Its motion speed relative to the receiver changes slowly. The 1s time interval is sufficient to capture the pseudorange dynamic changes such as Doppler frequency shift and ionospheric delay caused by satellite motion. At the same time, it avoids the waste of system resources due to excessively frequent parameter updates and achieves a balance between accuracy and efficiency.

[0032] The navigation message contains key information such as satellite ephemeris and clock parameters, which are necessary data for the receiver to identify the satellite and calculate its position. In this embodiment, the message is made realistic through caching and dynamic injection. Specifically, during the signal generation process, the cached satellite ephemeris and clock parameters are dynamically injected into the analog signal, so that the analog signal is not only consistent with the real satellite signal in terms of time and pseudorange, but also has complete navigation data characteristics, further ensuring that the general GNSS receiver can be interpreted normally.

[0033] This embodiment addresses the problem that existing positioning schemes cannot fully simulate real satellite signals, leading to receivers' inability to correctly interpret pseudorange information and low positioning accuracy. It proposes a time-synchronized pseudorange simulation method for BeiDou B1I signals to generate navigation signals consistent with real satellite signals in environments without satellite signals, thus inducing a general-purpose GNSS receiver to complete positioning. Specifically, time alignment is triggered by an external 1PPS pulse signal, combined with pseudorange transmission time and alignment delay calculated by the SDK, achieving nanosecond-level synchronization between the simulated signal and the real satellite signal. Based on the C / A code generation logic of the BeiDou B1I signal (G1 / G2 shift register XOR operation), pseudorange changes are simulated in real time. Finally, navigation potentials are buffered via FIFO, and satellite ephemeris and clock parameters are dynamically injected to enhance signal realism.

[0034] The technical solution provided in this embodiment can be widely applied to: Indoor positioning provides continuous navigation services in areas without satellite signals, such as shopping malls and underground parking lots. Autonomous driving tests generate virtual satellite signals in a closed environment to verify the robustness of the vehicle positioning system.

[0035] In some embodiments, the pseudorange distance deviation correction amount is obtained. include: The remaining chip count and current milliseconds are obtained in real time through an internal hardware counter and fed back to the SDK. Based on the remaining number of chips and the current number of milliseconds, and using the SDK algorithm, the pseudorange distance deviation correction amount is obtained. and accuracy adaptation parameters The accuracy adaptation parameters Used to process the pseudorange distance deviation correction amount The accuracy deviation.

[0036] In some embodiments, the SDK-issued NCO frequency control word and carrier NCO frequency control word include: Based on the pseudorange distance deviation correction amount By reverse calculation, the chip transmission time deviation and Doppler frequency shift can be obtained; The chip transmission time deviation is converted into a recognizable NCO frequency control word, and the Doppler frequency shift is converted into a recognizable carrier NCO frequency control word.

[0037] In some embodiments, triggering a hardware reset of the G1 / G2 shift register every 1ms includes: The C / A code of Beidou B1I has a complete chip cycle of 1ms. Every 1ms, the hardware reset of the G1 / G2 shift register is triggered, so that the corresponding shift register starts generating chips again from the initial phase.

[0038] In some embodiments, the hardware receives the NCO frequency control word and carrier NCO frequency control word sent by the SDK every 1 second, including: The NCO frequency is adjusted by the NCO frequency control word to compensate for changes in chip transmission time, so that the simulated C / A code is consistent with the arrival time of the real satellite signal. If the satellite is far from the receiver, the chip transmission time becomes longer, the NCO frequency control word of the code increases, and the NCO frequency of the code is adjusted to increase. If the satellite is close to the receiver, the chip transmission time becomes shorter, the NCO frequency control word of the code decreases, and the NCO frequency of the code is adjusted to decrease.

[0039] In some embodiments, the hardware receiving SDK-issued NCO frequency control word and carrier NCO frequency control word triggered every 1 second further include: The carrier NCO frequency is adjusted by the carrier NCO frequency control word to compensate for the Doppler frequency shift, so that the frequency shift characteristics of the analog carrier are consistent with the real satellite signal. If the satellite is close to the receiver, the carrier NCO frequency control word is increased, and the carrier NCO frequency is adjusted to rise. If the satellite moves away from the receiver, the carrier NCO frequency control word decreases, and the carrier NCO frequency is adjusted to decrease.

[0040] In some embodiments, the navigation message is cached via FIFO and satellite ephemeris and clock parameters are dynamically injected.

[0041] In some embodiments, by The module performs calculations of real-time pseudorange and convergence.

[0042] In some embodiments, the external time reference source uses 1PPS second pulses.

[0043] In some embodiments, the hardware is an FPGA module.

[0044] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computing software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0045] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0046] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A pseudorange simulation method for BeiDou B1I signals based on time synchronization, characterized in that, include: When initialization valid signal Upon triggering, the hardware loads the code issued by the SDK, including the initial frequency of the NCO and the initial phase of the G1 / G2 shift registers. The hardware detects the rising edge of the external time reference source and starts a delay counter. When the delay counter counts to reach the alignment delay threshold issued by the SDK, the hardware automatically activates signal generation enable. The hardware reset of the G1 / G2 shift register is triggered every 1ms, and the hardware receives the NCO frequency control word and carrier NCO frequency control word sent by the SDK every 1s, which together constitute the timing control algorithm. The real-time pseudorange is calculated using the following formula. The difference between the real-time pseudorange and the theoretical pseudorange is fed back to the SDK. Based on the difference, the damping factor parameter is dynamically adjusted to ensure that the real-time pseudorange calculation converges, and the converged pseudorange is obtained. This is the pseudorange distance deviation correction amount. The cumulative residual value of the code NCO; An initial C / A code is obtained by performing an XOR operation between the G1 shift register and the G2 shift register. The initial C / A code is then verified and adjusted using the timing control algorithm and the convergence pseudorange to obtain an analog C / A code. After performing an XOR operation between the analog C / A code and the navigation message, the signal is modulated onto the carrier wave and output as 8-bit IQ data to a digital-to-analog converter for digital-to-analog conversion, generating a BeiDou B1I radio frequency signal, which is an analog satellite signal.

2. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, The pseudorange distance deviation correction amount is obtained. include: The remaining chip count and current milliseconds are obtained in real time through an internal hardware counter and fed back to the SDK. Based on the remaining number of chips and the current number of milliseconds, and using the SDK algorithm, the pseudorange distance deviation correction amount is obtained. and accuracy adaptation parameters The accuracy adaptation parameters Used to process the pseudorange distance deviation correction amount The accuracy deviation.

3. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 2, characterized in that, The SDK-issued NCO frequency control word and carrier NCO frequency control word include: Based on the pseudorange distance deviation correction amount By reverse calculation, the chip transmission time deviation and Doppler frequency shift can be obtained; The chip transmission time deviation is converted into a recognizable NCO frequency control word, and the Doppler frequency shift is converted into a recognizable carrier NCO frequency control word.

4. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, The hardware reset of the G1 / G2 shift registers, triggered every 1ms, includes: The C / A code of Beidou B1I has a complete chip cycle of 1ms. Every 1ms, the hardware reset of the G1 / G2 shift register is triggered, so that the corresponding shift register starts generating chips again from the initial phase.

5. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, Every 1 second, the hardware receives the NCO frequency control word and carrier NCO frequency control word sent by the SDK. The NCO frequency is adjusted by the NCO frequency control word to compensate for changes in chip transmission time, so that the simulated C / A code is consistent with the arrival time of the real satellite signal. If the satellite is far from the receiver, the chip transmission time becomes longer, the NCO frequency control word of the code increases, and the NCO frequency of the code is adjusted to increase. If the satellite is close to the receiver, the chip transmission time becomes shorter, the NCO frequency control word of the code decreases, and the NCO frequency of the code is adjusted to decrease.

6. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 5, characterized in that, Every 1 second, the hardware receives the NCO frequency control word and carrier NCO frequency control word sent by the SDK. The carrier NCO frequency is adjusted by the carrier NCO frequency control word to compensate for the Doppler frequency shift, so that the frequency shift characteristics of the analog carrier are consistent with the real satellite signal. If the satellite is close to the receiver, the carrier NCO frequency control word is increased, and the carrier NCO frequency is adjusted to rise. If the satellite moves away from the receiver, the carrier NCO frequency control word decreases, and the carrier NCO frequency is adjusted to decrease.

7. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, The navigation message is cached in a FIFO and satellite ephemeris and clock parameters are dynamically injected.

8. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, pass The module performs calculations of real-time pseudorange and convergence.

9. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, The external time reference source uses 1PPS second pulses.

10. The pseudorange simulation method for BeiDou B1I signals based on time synchronization according to claim 1, characterized in that, The hardware is an FPGA module.

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