GNSS occultation signal tracking systems, methods, devices, and media

Abstract

The application discloses a GNSS occultation signal tracking system, method, device and medium, and relates to the field of atmospheric detection.The system comprises a control unit and a baseband signal processing unit, and the baseband signal processing unit comprises a plurality of correlator groups; the control unit calculates a first frequency and a first pseudo-range corresponding to a GNSS satellite in an occultation state in response to determining that a GNSS atmospheric occultation event exists; the baseband signal processing unit receives a digital intermediate frequency signal transmitted by an occultation radio frequency unit; a local carrier signal is generated according to the first frequency, and a local pseudo-code sequence is generated according to the first pseudo-range and the chip interval width of the plurality of correlator groups, and the code phases of the local pseudo-code sequence are different; each correlator group obtains a coherent integration result of an I / Q branch according to the digital intermediate frequency signal, the local carrier signal and the local pseudo-code sequence; and the baseband signal processing unit provides the coherent integration result with the highest signal strength to the control unit.The system improves the tracking range of the code phase and improves the detection success rate.

Description

Technical Field

[0001] This application relates to the field of atmospheric sounding technology, and in particular to a GNSS occultation signal tracking system, method, device and medium. Background Technology

[0002] GNSS (Global Navigation Satellite System) signals, as a core carrier of modern space information infrastructure, have traditionally focused on Position, Navigation, and Time (PNT) services. With the development of space exploration technology, a new detection method based on GNSS radio occultation has broken through the original application boundaries. By utilizing the refraction effect produced when GNSS signals received by low-Earth orbit satellites pass through the atmosphere, the physical parameters of the atmosphere and ionosphere can be accurately retrieved. This technology, by constructing a mathematical model of the phase delay, amplitude attenuation, and atmospheric refractive index along the signal path, can passively and in all weather conditions acquire global atmospheric temperature, humidity, and pressure vertical profiles. Its high retrieval accuracy provides high-resolution data for numerical weather prediction, ultimately improving weather forecast accuracy. In GNSS atmospheric occultation signal tracking, traditional signal tracking modes are mainly divided into closed-loop (CL) tracking and open-loop (OL) tracking. Closed-loop tracking utilizes a feedback system to calculate the phase difference between the received signal and the locally generated reference signal to adjust the phase and frequency of the local oscillator in real time, achieving high tracking accuracy. Its phase tracking results can be directly used for subsequent inversion calculations. However, in the lower atmosphere (especially the lower troposphere), due to the multipath effect caused by drastic changes in atmospheric refractive index gradient, rapid signal attenuation, and changes in Doppler frequency, closed-loop tracking is prone to lock-out, leading to discontinuous observation data and affecting the quality of subsequent inversion data. To compensate for the weak detection capability of closed-loop tracking in the lower atmosphere, open-loop tracking is typically used. Open-loop tracking mainly relies on parameter prediction based on ephemeris data, satellite PVT data, and atmospheric models to achieve tracking. Figure 1 A schematic diagram illustrating the principle of open-loop tracking is shown. For example... Figure 1 As shown, the working process of open-loop tracking technology includes: (1) Signal input and preprocessing: The GNSS signal is processed by the receiver and then input into the system, and preprocessed, such as filtering and amplification; (2) Local signal generation: The local carrier signal is generated by the local carrier NCO, and the local reference signal with the corresponding pseudocode is generated by the local code phase NCO (Numerically Controlled Oscillator), where (3) The input signal is multiplied by the local carrier and the local pseudocode signal respectively, and then the results are summed and squared. Useful information in the signal is extracted through correlation integration and provided to the open-loop tracking control module; (4) Open-loop control and parameter prediction: The open-loop tracking control module predicts the Doppler frequency shift of the signal based on prior information such as satellite orbit and atmospheric model, and provides frequency control basis for the local carrier NCO. Combined with the orbit data of the satellite and receiver, it predicts the pseudorange change and provides phase control parameters for the local code phase NCO. Figure 1 It is known that open-loop tracking technology does not rely on signal feedback adjustment mechanisms. Instead, it predicts the Doppler frequency and pseudorange of the signal based on orbital dynamics models and atmospheric refractive index climatology models, directly generating a local reference signal for correlation processing with the received signal. This method has stronger tracking capabilities in the lower atmosphere and is more suitable for occultation signal tracking. After adopting open-loop tracking, more than 90% of occultation detections can penetrate to below 1 km in high-latitude regions and more than 70% in tropical regions.

[0003] Existing open-loop tracking technology for GNSS occultation detection can partially solve the problem of discontinuities in lower atmospheric data. This method mainly focuses on the Doppler frequency dimension, and the difference between the predicted frequency and the true Doppler frequency can be within 0.5 Hz, achieving high accuracy. However, this method lacks accuracy in calculating the code phase dimension (pseudorange). When tracking satellites at low tangent altitudes, especially for rising occultation events and complex dynamic environments in the lower atmosphere, existing methods exhibit large tracking errors, with prediction accuracy errors reaching 200 meters or even higher. In actual tracking, when the deviation between the predicted pseudorange and the true pseudorange exceeds half a chip, the signal strength weakens significantly. When the error exceeds one chip, there is no signal at all, and the detected data cannot be used for subsequent inversion. Using traditional open-loop tracking methods, the prediction results are prone to exceeding tracking limits, leading to poor final detection results. Summary of the Invention

[0004] To solve the above-mentioned technical problems, or at least partially solve them, embodiments of this application provide a GNSS occultation signal tracking system, method, electronic device, and medium.

[0005] In a first aspect, embodiments of this application provide a GNSS occultation signal tracking system. The system includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes a multiple correlator module, which includes multiple correlator groups. The chip spacing widths of the multiple correlator groups are different or the same. In response to determining the existence of a GNSS atmospheric occultation event, the control unit calculates the first frequency and the first pseudorange corresponding to the GNSS satellite in the occultation state, and provides the first frequency and the first pseudorange as tracking guidance parameters to the baseband signal processing unit. The baseband signal processing unit receives the digital intermediate frequency signal transmitted by the occultation radio frequency unit; generates a local carrier signal according to the first frequency, generates a local pseudocode sequence according to the first pseudorange and the chip spacing width of the multiple correlator groups, and provides the digital intermediate frequency signal, the local carrier signal and the local pseudocode sequence to the multiple correlator groups; the code phases of the local pseudocode sequences are different. Each correlator group performs coherent integration based on the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group; The baseband signal processing unit provides the control unit with the coherent integration result with the highest signal strength among the coherent integration results of the multiple correlator groups.

[0006] Optionally, the multiple correlator groups operate in parallel and synchronously.

[0007] Optionally, the control unit includes an open-loop tracking control module, a frequency prediction module, and a pseudorange prediction module; The open-loop tracking control module calculates the relative geometric position information of each GNSS satellite based on the current status information of the GNSS occultation detector and the ephemeris of each GNSS satellite received by the GNSS occultation detector, in order to determine whether a GNSS atmospheric occultation event is currently occurring. The frequency prediction module calculates the first frequency corresponding to the GNSS satellite in occultation state based on the relative geometric motion and atmospheric propagation model of LEO satellite and GNSS satellite; The pseudorange prediction module calculates the first pseudorange corresponding to the GNSS satellite in an occultation state based on the relative geometric motion and atmospheric propagation model of LEO satellites and GNSS satellites.

[0008] Optionally, the open-loop tracking control module is further configured to set open-loop tracking parameters and provide the open-loop tracking parameters to the baseband signal processing unit. The open-loop tracking parameters include one or more of the following: chip spacing width of each correlator group, correlator order, and preset peak position.

[0009] Optionally, the baseband signal processing unit stores the received open-loop tracking parameters in a non-volatile memory.

[0010] Optionally, the open-loop tracking control module is also used to receive the coherent integration result provided by the baseband signal processing unit and transmit the received coherent integration result to the satellite platform.

[0011] Optionally, the open-loop tracking control module is further configured to package the received coherent integration result with the corresponding additional information, send the obtained data packet to the data buffer queue, and transmit the data packet to the satellite platform in the order of the data buffer queue.

[0012] Optionally, the frequency prediction module calculates the first frequency according to the following formula (1): (1) in, Indicates the first frequency. Represents the geometric Doppler component. This indicates the additional Doppler component of the ionosphere. This indicates the additional Doppler component of the atmosphere. This represents the atmospheric refraction with added Doppler component, and t represents the current time.

[0013] Optionally, the pseudorange prediction module fits the first pseudorange based on the light speed propagation delay, ionospheric propagation delay, and atmospheric propagation delay of the Euclidean distance between the GNSS satellite and the LEO satellite.

[0014] Optionally, the pseudorange prediction module calculates the first pseudorange according to the following formula (2): (2) in, Indicates the first pseudorange. The propagation delay of light at the Euclidean distance between GNSS and LEO satellites. , Indicates ionospheric propagation delay. This indicates a delay in atmospheric propagation.

[0015] Optionally, the baseband signal processing unit includes a local carrier numerically controlled oscillator module; The local carrier numerically controlled oscillator module generates a local carrier signal based on the first frequency and phase update relationship.

[0016] Optionally, the local carrier numerically controlled oscillator module generates a local carrier signal according to the following formula (3):

[0017] in, express The phase of the local carrier signal at time t. Indicates the sampling period. Indicates the bit width of the phase accumulator. Indicates the sampling frequency. Indicates the first frequency. The local carrier signal generated by the local carrier numerically controlled oscillator module. Indicates the imaginary part.

[0018] Optionally, the baseband signal processing unit includes a local multi-code phase digitally controlled oscillator module; The local multi-code phase numerically controlled oscillator module generates a local pseudocode sequence based on the first pseudorange and open-loop tracking parameters.

[0019] Optionally, the local multi-code phase numerically controlled oscillator module generates a local pseudocode sequence according to the following formula (4):

[0020] in, This is the current sampling time point. This is the accumulated value of the public code phase. For the first Local code phase of the path correlator For pseudo-code bitrate, Sampling frequency, Let be the rate of change of pseudorange at time t. At the speed of light, This indicates the location of the correlator peak in the prediction. The code phase interval between adjacent correlators. , Indicates the width of the correlator chip interval. This represents the total number of correlators. For local pseudocode generator, The pseudocode length, For the first The local pseudocode value generated by the path correlator.

[0021] Optionally, each correlator group generates a local complex sampled baseband signal based on the digital intermediate frequency signal and the local carrier signal; and performs coherent integration operation on the local complex sampled baseband signal and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group.

[0022] Optionally, the correlator group obtains the coherent integration result of the I / Q branch according to the following equation (5):

[0023] in, Indicates the current sampling time. It is a digital intermediate frequency signal. For the local carrier NCO phase, For the first The local pseudocode sequence corresponding to the path correlator, For the coherent integration time, and The first The coherent integral results of the in-phase and quadrature branches of the path correlator For complex correlation output, This represents the total number of correlators.

[0024] Optionally, the correlator group includes: a first multiplier, a plurality of second multipliers, a plurality of summers, and a plurality of modular square operators, wherein the number of second multipliers, summers, and modular square operators are equal and correspond one-to-one; The first multiplier receives the digital intermediate frequency signal and the local carrier signal, performs a multiplication operation on the digital intermediate frequency signal and the local carrier signal to obtain a local complex sampled baseband signal, and provides the local complex sampled baseband signal to the second multiplier; The second multiplier performs a multiplication operation on the local complex sampled baseband signal and the local pseudocode sequence to obtain a first operation result, and provides the first operation result to the corresponding summer; The summer performs a summation operation on the first operation result to obtain a second operation result, and provides the second operation result to the corresponding modulo square operator; The modular square operator performs a square operation on the second operation result to obtain the coherent integral result.

[0025] Optionally, the baseband signal processing unit further includes a peak value determination module; Each correlator group provides the coherent integration result of the I / Q branch of the correlator group module to the peak value determination module; The peak value determination module receives the coherent integration results of the I / Q branches of each correlator group, calculates the signal strength of each coherent integration result, and provides the coherent integration result with the largest signal strength to the open-loop tracking control module.

[0026] Optionally, the peak determination module calculates the signal strength of the coherent integral result according to the following formula (6): (6) This represents the coherent integral result with the highest signal strength. This represents the number of correlator groups.

[0027] Secondly, this application provides a GNSS occultation signal tracking method. The method is applied to the GNSS occultation signal tracking system described in any embodiment of this application. The system includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes a multiple correlator module. The multiple correlator module includes multiple correlator groups. The chip spacing width of the multiple correlator groups is different or the same. The method includes: In response to determining the existence of a GNSS atmospheric occultation event, the control unit calculates the first frequency and the first pseudorange corresponding to the GNSS satellite in the occultation state, and provides the first frequency and the first pseudorange as tracking guidance parameters to the baseband signal processing unit. The baseband signal processing unit receives the digital intermediate frequency signal transmitted by the occultation radio frequency unit; generates a local carrier signal according to the first frequency, generates a local pseudocode sequence according to the first pseudorange and the chip spacing width of the multiple correlator groups, and provides the digital intermediate frequency signal, the local carrier signal and the local pseudocode sequence to the multiple correlator groups; the code phases of the local pseudocode sequences are different. Each correlator group performs coherent integration based on the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group; The baseband signal processing unit provides the control unit with the coherent integration result with the highest signal strength among the coherent integration results of the multiple correlator groups.

[0028] Thirdly, embodiments of this application provide an electronic device, including a processor and a field-programmable gate array (FPGA). The processor includes a control unit provided in any embodiment of this application, and the FPGA includes a baseband signal processing unit provided in any embodiment of this application.

[0029] Fourthly, embodiments of this application provide a readable storage medium storing a program or instructions, which, when executed by a processor, implement the GNSS occultation signal tracking method provided in any embodiment of this application.

[0030] The GNSS occultation signal tracking system provided in this application includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes multiple correlator groups with different chip spacing widths. In response to determining the existence of a GNSS atmospheric occultation event, the control unit calculates the first frequency and first pseudorange corresponding to the occulted GNSS satellite and provides this first frequency and first pseudorange as tracking guidance parameters to the baseband signal processing unit. The control unit performs open-loop tracking in the Doppler frequency dimension. The baseband signal processing unit includes multiple parallel correlator groups and performs tracking in the code phase dimension. The multiple parallel correlator groups simultaneously calculate the code phase based on the first frequency and first pseudorange predicted by the control unit, obtaining multiple sets of code phases, and then obtaining the coherent integration results of the I / Q branches of the multiple correlator groups. This not only enables accurate prediction of the Doppler frequency but also greatly improves the dynamic range of pseudorange tracking. This application significantly improves the tracking range of the code phase by setting up multiple sets of pseudo-code correlators, predicting and incorporating multiple sets of code phases, and simultaneously acquiring multiple sets of correlation results. This solves the problems of inaccurate code phase prediction and weak tracking signals in existing technologies under high dynamic conditions at low tangent altitudes, and significantly improves the detection success rate and data quality of occultation events in the lower atmosphere (especially below 5km). Compared to existing technologies, the GNSS occultation signal tracking system in this application requires no hardware modifications and is fully compatible with existing receiver solutions. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0032] Figure 1 The schematic diagram of open-loop tracking technology is shown; Figure 2 A block diagram of a GNSS occultation signal tracking system according to an embodiment of this application is shown; Figure 3 A block diagram of a GNSS occultation signal tracking system according to another embodiment of this application is shown; Figure 4 A block diagram of a GNSS occultation signal tracking system according to yet another embodiment of this application is shown; Figure 5 A flowchart illustrating a GNSS occultation signal tracking method according to an embodiment of this application is provided. Detailed Implementation

[0033] 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, 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.

[0034] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0035] Figure 2 A block diagram of a GNSS occultation signal tracking system according to an embodiment of this application is shown.

[0036] like Figure 2 As shown, the GNSS occultation signal tracking system 200 includes a control unit 201 and a baseband signal processing unit 202. The baseband signal processing unit 202 includes a multiple correlator module 2021, which comprises multiple correlator groups 20211, with different or identical chip spacing widths for each correlator group 20211. The chip spacing width of each correlator group 20211 is configurable.

[0037] In response to determining that a GNSS atmospheric occultation event exists, the control unit 201 calculates the first frequency and first pseudorange corresponding to the GNSS satellite in the occultation state, and provides the first frequency and first pseudorange as tracking guidance parameters to the baseband signal processing unit.

[0038] When a GNSS satellite signal passes through the Earth's atmosphere from the edge and is received by a LEO satellite, the signal propagation path is bent and delayed due to changes in atmospheric density, temperature, water vapor, and ionospheric electron density. GNSS atmospheric occultation events are detected by dedicated receivers, such as GNSS occultation detectors, on LEO satellites (Low Earth Orbit Satellites). When an LEO satellite and a GNSS satellite move relative to each other to the Earth's edge (near the horizon), the GNSS signal path just passes through the atmosphere, forming an "occultation geometry," at which point the GNSS satellite is in an occultation state. If there are GNSS satellites in an occultation state, a GNSS atmospheric occultation event is determined to exist. In an optional embodiment, the control unit 201 can determine whether each GNSS satellite is in an occultation state based on the geometric relationship between the GNSS occultation detector and each GNSS satellite; if there are GNSS satellites in an occultation state, a GNSS atmospheric occultation event is determined to exist.

[0039] When a GNSS atmospheric occultation event is determined to exist, the control unit 201 calculates a first frequency and a first pseudorange, for example, based on the relative geometric motion and atmospheric propagation model of the LEO satellite and the GNSS satellite. Pseudorange is a core observation used for positioning in a Global Navigation Satellite System (GNSS), referring to the non-real distance between the satellite and the receiver calculated by multiplying the signal propagation time by the speed of light.

[0040] The baseband signal processing unit 202 generates a local carrier signal based on the first frequency and a local pseudocode sequence based on the first pseudorange; it receives the digital intermediate frequency signal transmitted by the occultation radio frequency unit and provides the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to multiple correlator groups 20211.

[0041] The local carrier signal refers to a high-frequency sine wave signal generated locally by the baseband signal processing unit for modulation or demodulation. It does not carry information itself but serves as a carrier for information transmission. Optionally, the baseband signal processing unit 202 drives the local carrier signal generation unit to generate a local carrier signal according to a first frequency.

[0042] The local pseudocode sequence includes multiple code phases. Optionally, the baseband signal processing unit 202 generates multiple code phases based on the first pseudorange and preset correlator parameters, such as the preset peak position of the correlator, the correlator order, and the chip spacing width of the correlator (the time interval between two adjacent chips).

[0043] Digital intermediate frequency (IF) signal refers to the signal obtained after the occultation signal is received by the corresponding occultation antenna, amplified, filtered, and down-converted by the radio frequency front-end, and then sampled by an A / D (analog-to-digital converter). Occultation signal refers to the radio wave signal emitted by a global navigation satellite system, whose propagation path is bent and delayed due to atmospheric refraction as it passes through the Earth's atmosphere.

[0044] Each correlator group 20211 performs coherent integration operations based on the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to obtain the coherent integration results of the I-branch (in-phase branch) and Q-branch (quadrature branch) of the correlator group. The chip spacing widths of the multiple correlator groups 20211 are different, for example, 1, 0.5, 0.25, and 0.125 chips respectively. The multiple correlator groups 20211 operate in parallel and synchronously. Coherent integration is a computational operation in signal processing that enhances the signal-to-noise ratio and eliminates noise effects by accumulating signals with consistent phase over a specific time period. In this embodiment, each correlator group 20211 first mixes the digital intermediate frequency signal with the local carrier signal to generate a local complex sampled baseband signal, and then correlates the local complex sampled baseband signal with local pseudocode sequences of different chip delays to obtain the coherent integration results of the I-branch and Q-branch of each correlator group.

[0045] The baseband signal processing unit provides the control unit with the coherent integration result with the highest signal strength from the coherent integration results of multiple correlator groups.

[0046] The GNSS occultation signal tracking system provided in this application includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes multiple correlator groups with different chip spacing widths. In response to determining the existence of a GNSS atmospheric occultation event, the control unit calculates the first frequency and first pseudorange corresponding to the occulted GNSS satellite and provides these parameters to the baseband signal processing unit as tracking guidance parameters. The control unit performs open-loop tracking in the Doppler frequency dimension. The baseband signal processing unit includes multiple parallel correlator groups and performs tracking in the code phase dimension. The multiple parallel correlator groups simultaneously calculate the code phase based on the first frequency and first pseudorange predicted by the control unit, obtaining multiple sets of code phases, and then obtaining the coherent integration results of the I / Q branches of the multiple correlator groups. This not only enables accurate prediction of the Doppler frequency but also significantly improves the dynamic range of pseudorange tracking. This application significantly improves the tracking range of the code phase by setting up multiple sets of pseudo-code correlators, predicting and incorporating multiple sets of code phases, and simultaneously acquiring multiple sets of correlation results. This solves the problems of inaccurate code phase prediction and weak tracking signals in existing technologies under high dynamic conditions at low tangent altitudes, and significantly improves the detection success rate and data quality of occultation events in the lower atmosphere (especially below 5km). Compared to existing technologies, the GNSS occultation signal tracking system in this application requires no hardware modifications and is fully compatible with existing receiver solutions.

[0047] The GNSS occultation signal tracking system provided in this application is applied to an atmospheric occultation detector to achieve stable and uninterrupted tracking of highly dynamic, low signal-to-noise ratio atmospheric occultation signals. The system simultaneously performs coherent integration and peak discrimination of multiple signals through multiple sets of parallel correlators and multiple pseudocode phase predictions designed in an FPGA. Combined with dynamically configurable tracking parameters to adapt to multiple GNSS signal standards, it outputs high-precision observation values ​​while maintaining unchanged hardware interfaces and data formats and without affecting backend atmospheric inversion calculations. This provides more reliable and higher-quality data support for the inversion of atmospheric parameters such as temperature, humidity, and pressure. This application is applied to the fields of Global Navigation Satellite System (GNSS) occultation detection and atmospheric remote sensing, and represents a novel method and system for atmospheric occultation signal tracking on a GNSS occultation detector.

[0048] Figure 3 A block diagram of a GNSS occultation signal tracking system according to an embodiment of this application is shown. Figure 3As shown, the GNSS occultation signal tracking system 300 includes a control unit 301 and a baseband signal processing unit 302. The control unit 301 is responsible for the overall control of the system, and the baseband signal processing unit 302 is responsible for high-speed signal processing. The control unit 301 includes an open-loop tracking control module 3011, a frequency prediction module 3012, and a pseudorange prediction module 3013. The baseband signal processing unit 302 includes a multiple correlator module 3021, a local carrier numerically controlled oscillator module 3022, a local multiple code phase numerically controlled oscillator module 3023, and a peak value determination module 3024. The multiple correlator module 3021 includes multiple correlator groups 30211, and the chip spacing widths of the multiple correlator groups 30211 are different.

[0049] The open-loop tracking control module 3011 calculates the relative geometric position information of each GNSS satellite based on the current status information of the GNSS occultation detector and the ephemeris data of each GNSS satellite received by the GNSS occultation detector, in order to determine whether a GNSS atmospheric occultation event is currently occurring. For example, the open-loop tracking control module 3011 calculates the relative geometric position information of each GNSS satellite based on the position, velocity, and time information of the LEO satellite to which the GNSS occultation detector is located, as well as the valid ephemeris data of each GNSS satellite received, and determines whether a GNSS atmospheric occultation event has occurred.

[0050] Optionally, the open-loop tracking control module 3011 is also used to set tracking parameters and provide the open-loop tracking parameters to the baseband signal processing unit. The open-loop tracking parameters include one or more of the following: chip spacing width of each correlator group (e.g., 1, 0.5, 0.25, 0.125 chips), correlator order, and preset peak position. Optionally, the baseband signal processing unit stores the received open-loop tracking parameters in non-volatile memory.

[0051] The frequency prediction module 3012 calculates the first frequency corresponding to the GNSS satellite in occultation state based on the relative geometric motion and atmospheric propagation model of the LEO satellite and the GNSS satellite. For example, the frequency prediction module 3012 calculates the first frequency according to the following formula (1): (1) in, Indicates the first frequency. Represents the geometric Doppler component. This indicates the additional Doppler component of the ionosphere. This indicates the additional Doppler component of the atmosphere. This represents the atmospheric refraction with added Doppler component, and t represents the current time.

[0052] The pseudorange prediction module 3013 calculates the first pseudorange corresponding to the GNSS satellite in the occultation state based on the relative geometric motion and atmospheric propagation model between the LEO satellite and the GNSS satellite. For example, as shown in Equation (2) below, the pseudorange prediction module 3013 fits the first pseudorange according to the light speed propagation delay, ionospheric propagation delay and atmospheric propagation delay of the Euclidean distance between the GNSS satellite and the LEO satellite.

[0053] (2) in, Indicates the first pseudorange. The propagation delay of light at the Euclidean distance between GNSS and LEO satellites. , Indicates ionospheric propagation delay. This indicates a delay in atmospheric propagation.

[0054] This application embodiment sets tracking parameters through an open-loop tracking control module, enabling the system to dynamically inject and flexibly configure parameters. This significantly improves the system's applicability and scenario adaptability. It can flexibly adjust the phase interval width between each group of correlators through dynamic parameter configuration for different navigation signal standards and their corresponding differential code rates. This adaptively matches the pseudocode characteristics of different signals and dynamically adjusts the pseudorange tracking range. Simultaneously, it can dynamically set the preset position of the correlation peak and the correlator order based on the orbital altitude, signal dynamic characteristics, and detection mission requirements of the occultation detection. This achieves efficient adaptation of the tracking architecture to signal characteristics and detection scenarios, and is compatible with GNSS atmospheric occultation signal tracking processing under multiple frequency points, multiple code types, and multiple dynamic conditions. This effectively expands the system's application scenarios and scope, and significantly improves the versatility, scalability, and engineering deployment flexibility of the two-dimensional open-loop tracking method.

[0055] The local carrier numerically controlled oscillator module 3022 generates a local carrier signal based on the first frequency and phase update relationship. Optionally, the local carrier numerically controlled oscillator module 3022 generates the local carrier signal according to the following formula (3):

[0056] in, express The phase of the local carrier signal at time t. Indicates the sampling period. Indicates the bit width of the phase accumulator. Indicates the sampling frequency. Indicates the first frequency. The local carrier signal generated by the local carrier numerically controlled oscillator module. Indicates the imaginary part.

[0057] The local multi-code phase numerically controlled oscillator module 3023 generates a local pseudocode sequence based on the first pseudorange and the open-loop tracking parameters. Optionally, the local multi-code phase numerically controlled oscillator module 3023 generates the local pseudocode sequence according to the following formula (4):

[0058] in, This is the current sampling time point. This is the accumulated value of the public code phase. For the first Local code phase of the path correlator For pseudo-code bitrate, Sampling frequency, Let be the rate of change of pseudorange at time t. At the speed of light, This indicates the location of the correlator peak in the prediction. The code phase interval between adjacent correlators. , Indicates the width of the correlator chip interval. This represents the total number of correlators. For local pseudocode generator, The pseudocode length, For the first The local pseudocode value generated by the path correlator.

[0059] Optionally, each correlator group 30211 generates a local complex sampled baseband signal based on the digital intermediate frequency signal and the local carrier signal; and performs coherent integration operation on the local complex sampled baseband signal and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group.

[0060] Optionally, the correlator array obtains the coherent integral result of the I / Q branch according to the following equation (5):

[0061] in, Indicates the current sampling time. It is a digital intermediate frequency signal. For the local carrier NCO phase, For the first The local pseudocode sequence corresponding to the path correlator, For the coherent integration time, and The first The coherent integral results of the in-phase and quadrature branches of the path correlator For complex correlation output, This represents the total number of correlators.

[0062] Each correlator group 30211 provides the coherent integration results of the I / Q branches to the peak value determination module 3024.

[0063] The peak determination module 3024 receives the coherent integration results of the I / Q branches of each correlator group, calculates the signal strength of each coherent integration result, and provides the coherent integration result with the highest signal strength to the open-loop tracking control module. Optionally, the peak determination module 3024 calculates the signal strength of the coherent integration result according to the following formula (6): (6) This represents the coherent integral result with the highest signal strength, where M is the number of correlator groups.

[0064] The open-loop tracking control module 3011 receives the coherent integration result provided by the baseband signal processing unit and transmits the received coherent integration result to the satellite platform. Optionally, the open-loop tracking control module is also used to package the received coherent integration result with the corresponding additional information, send the obtained data packet to the data buffer queue, and transmit the data packet to the satellite platform according to the order of the data buffer queue.

[0065] This application's embodiments incorporate a multiple correlator, a local multiple code phase numerically controlled oscillator module, and a peak value detector within the baseband signal processing unit (FPGA). A parallel hardware architecture is employed to achieve synchronous prediction of multiple sets of pseudocode phases and parallel correlation processing of multiple signals. This addresses the pain points of lock-loss and discontinuous detection data in high-dynamic, low-signal-to-noise-ratio, and large pseudorange variation scenarios in GNSS atmospheric occultation detection. Simultaneously, it overcomes the shortcomings of traditional single-dimensional open-loop tracking, which only focuses on the carrier or pseudocode dimension and has poor pseudorange error tolerance, achieving stable and high-precision reliable tracking of occultation signals.

[0066] Figure 4 A block diagram of a GNSS occultation signal tracking system according to yet another embodiment of this application is shown. Figure 3 Based on the GNSS occultation signal system shown, Figure 4 The GNSS occultation signal tracking system shown illustrates the multiple correlator group module and the block diagram of each correlator group. For example... Figure 4As shown, the GNSS occultation signal tracking system 400 includes a control unit 401 and a baseband signal processing unit 402. The control unit 401 is responsible for the overall control of the system, and the baseband signal processing unit 402 is responsible for high-speed signal processing. The control unit 401 includes an open-loop tracking control module 4011, a frequency prediction module 4012, and a pseudorange prediction module 4013. The baseband signal processing unit 402 includes a multiple correlator module 4021, a local carrier numerically controlled oscillator module 4022, a local multiple code phase numerically controlled oscillator module 4023, and a peak value determination module 4024. The multiple correlator module 4021 includes multiple correlator groups 40211, and the chip spacing widths of the multiple correlator groups 40211 are different.

[0067] like Figure 4 As shown, the multiple correlator module 4021 includes a first multiplier G1 and multiple correlator groups 40211. Each correlator group includes a second multiplier G2, a summer C1, and a modular square operator D1. The number of second multipliers G2, summer C1, and modular square operators D1 are equal and correspond one-to-one.

[0068] The first multiplier G1 receives the digital intermediate frequency signal and the local carrier signal, performs multiplication on the digital intermediate frequency signal and the local carrier signal to obtain the local complex sampled baseband signal, and provides the local complex sampled baseband signal to the second multiplier.

[0069] The second multiplier G2 performs multiplication operations based on the local complex sampled baseband signal and the local pseudocode sequence to obtain the first operation result, and provides the first operation result to the corresponding summer.

[0070] The summer C1 sums the first result to obtain the second result, and then provides the second result to the corresponding modulo square operator.

[0071] The modular square operator D1 squares the result of the second operation to obtain the coherent integral result.

[0072] Compared to existing open-loop / closed-loop GNSS occultation signal tracking technologies, the GNSS occultation signal tracking system provided in this application has excellent engineering compatibility and ease of iteration. It requires no structural modifications or hardware upgrades to the original hardware platform, RF link, and processing circuitry. The deployment of the two-dimensional open-loop tracking mechanism in this application embodiment can be completed solely through software algorithm optimization and logic reconfiguration at the FPGA and ARM levels. Furthermore, the improved algorithm does not interfere with or have any additional impact on subsequent atmospheric parameter inversion calculations. The data transmission format and interaction protocol remain unchanged, and the input / output interfaces, timing logic, and data interaction methods of the processing module are fully compatible with traditional tracking loops. It can directly and seamlessly replace existing tracking modules, greatly reducing system upgrade and transformation costs and engineering deployment difficulty. While ensuring equipment versatility and inheritability, it effectively improves occultation signal tracking capabilities.

[0073] Figure 5 A flowchart of a GNSS occultation signal tracking method according to an embodiment of this application is shown. This GNSS occultation method is applied to a GNSS occultation signal tracking system provided in another embodiment of this application. (Refer to...) Figure 2 - Figure 4 The GNSS occultation signal tracking system includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes a multiple correlator module, which includes multiple correlator groups. The chip spacing widths of the multiple correlator groups are different or the same.

[0074] like Figure 5 As shown, this GNSS occultation signal tracking method includes: Step S501: In response to determining that a GNSS atmospheric occultation event exists, the control unit calculates the first frequency and first pseudorange corresponding to the GNSS satellite in the occultation state, and provides the first frequency and first pseudorange as tracking guidance parameters to the baseband signal processing unit.

[0075] Step S502: The baseband signal processing unit generates a local carrier signal according to the first frequency, and generates a local pseudocode sequence according to the first pseudorange and the chip spacing width of multiple correlator groups. The code phases of the local pseudocode sequences are different. The unit receives the digital intermediate frequency signal transmitted by the occultation radio frequency unit and provides the digital intermediate frequency signal, the local carrier signal and the local pseudocode sequence to multiple correlator groups.

[0076] Step S503: Each correlator group performs coherent integration based on the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group.

[0077] Step S504: The baseband signal processing unit provides the control unit with the coherent integration result with the highest signal strength among the coherent integration results of multiple correlator groups.

[0078] In another embodiment provided in this application, an electronic device is provided, including a processor ARM and a field-programmable gate array (FPGA). The processor ARM includes a control unit in the GNSS occultation signal tracking system of any embodiment of this application, and the field-programmable gate array (FPGA) includes a baseband signal processing unit in the GNSS occultation signal tracking system of any embodiment of this application.

[0079] Fourthly, embodiments of this application provide a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, it implements the GNSS occultation signal tracking method provided in any embodiment of this application.

[0080] In another embodiment provided in this application, a computer-readable storage medium is also provided, which stores instructions that, when executed on a computer, cause the computer to perform any of the GNSS occultation signal tracking methods described in the above embodiments.

[0081] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute any of the GNSS occultation signal tracking methods in the above embodiments.

[0082] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another.

[0083] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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 limitations, 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 said element.

[0084] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0085] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A GNSS occultation signal tracking system, characterized in that, The system includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes a multiple correlator module, which includes multiple correlator groups. The chip spacing widths of the multiple correlator groups are different or the same. In response to determining the existence of a GNSS atmospheric occultation event, the control unit calculates the first frequency and the first pseudorange corresponding to the GNSS satellite in the occultation state, and provides the first frequency and the first pseudorange as tracking guidance parameters to the baseband signal processing unit. The baseband signal processing unit receives the digital intermediate frequency signal transmitted by the occultation radio frequency unit; generates a local carrier signal according to the first frequency, generates a local pseudocode sequence according to the first pseudorange and the chip spacing width of the multiple correlator groups, and provides the digital intermediate frequency signal, the local carrier signal and the local pseudocode sequence to the multiple correlator groups; the code phases of the local pseudocode sequences are different. Each correlator group performs coherent integration based on the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group; The baseband signal processing unit provides the control unit with the coherent integration result with the highest signal strength among the coherent integration results of the multiple correlator groups.

2. The system according to claim 1, characterized in that, The multiple correlator groups operate in parallel and synchronously.

3. The system according to claim 1, characterized in that, The control unit includes an open-loop tracking control module, a frequency prediction module, and a pseudorange prediction module; The open-loop tracking control module calculates the relative geometric position information of each GNSS satellite based on the current status information of the GNSS occultation detector and the ephemeris of each GNSS satellite received by the GNSS occultation detector, in order to determine whether a GNSS atmospheric occultation event is currently occurring. The frequency prediction module calculates the first frequency corresponding to the GNSS satellite in occultation state based on the relative geometric motion and atmospheric propagation model of LEO satellite and GNSS satellite; The pseudorange prediction module calculates the first pseudorange corresponding to the GNSS satellite in an occultation state based on the relative geometric motion and atmospheric propagation model of LEO satellites and GNSS satellites.

4. The system according to claim 3, characterized in that, The open-loop tracking control module is also used to set open-loop tracking parameters and provide the open-loop tracking parameters to the baseband signal processing unit. The open-loop tracking parameters include one or more of the following: chip spacing width of each correlator group, correlator order, and preset peak position.

5. The system according to claim 4, characterized in that, The baseband signal processing unit stores the received open-loop tracking parameters in a non-volatile memory.

6. The system according to claim 3 or 4, characterized in that, The open-loop tracking control module is also used to receive the coherent integration result provided by the baseband signal processing unit and transmit the received coherent integration result to the satellite platform.

7. The system according to claim 5, characterized in that, The open-loop tracking control module is also used to package the received coherent integration results with the corresponding additional information, send the obtained data packets to the data buffer queue, and transmit the data packets to the satellite platform in the order of the data buffer queue.

8. The system according to claim 3, characterized in that, The frequency prediction module calculates the first frequency according to the following formula (1): （1） in, Indicates the first frequency. Represents the geometric Doppler component. This indicates the additional Doppler component of the ionosphere. This indicates the additional Doppler component of the atmosphere. This represents the atmospheric refraction with additional Doppler component, and t represents the current time.

9. The system according to claim 3, characterized in that, The pseudorange prediction module obtains the first pseudorange by fitting the light speed propagation delay, ionospheric propagation delay, and atmospheric propagation delay of the Euclidean distance between the GNSS satellite and the LEO satellite.

10. The system according to claim 9, characterized in that, The pseudorange prediction module calculates the first pseudorange according to the following formula (2): （2） in, Indicates the first pseudorange. The propagation delay of light at the Euclidean distance between GNSS and LEO satellites. , Indicates ionospheric propagation delay. The speed of light is represented by c, which indicates the atmospheric propagation delay. This represents the Euclidean distance between GNSS satellites and LEO satellites.

11. The system according to claim 1, characterized in that, The baseband signal processing unit includes a local carrier numerically controlled oscillator module; The local carrier numerically controlled oscillator module generates a local carrier signal based on the first frequency and phase update relationship.

12. The system according to claim 11, characterized in that, The local carrier numerically controlled oscillator module generates the local carrier signal according to the following formula (3): in, express The phase of the local carrier signal at time t. Indicates the sampling period. Indicates the bit width of the phase accumulator. Indicates the sampling frequency. Indicates the first frequency. For the corresponding actual carrier phase, The local carrier signal generated by the local carrier numerically controlled oscillator module. Indicates the imaginary part.

13. The system according to claim 1 or 11, characterized in that, The baseband signal processing unit includes a local multi-code phase digitally controlled oscillator module; The local multi-code phase numerically controlled oscillator module generates a local pseudocode sequence based on the first pseudorange and open-loop tracking parameters.

14. The system according to claim 13, characterized in that, The local multi-code phase digitally controlled oscillator module generates the local pseudocode sequence according to the following formula (4): in, This is the current sampling time point. This is the accumulated value of the public code phase. For the first Local code phase of the path correlator For pseudo-code bitrate, Sampling frequency, Let be the rate of change of pseudorange at time t. At the speed of light, This indicates the location of the correlator peak in the prediction. The code phase interval between adjacent correlators. , Indicates the width of the correlator chip interval. This represents the total number of correlators. For local pseudocode generator, The pseudocode length, For the first The local pseudocode value generated by the path correlator.

15. The system according to claim 1, characterized in that, Each correlator group generates a local complex sampled baseband signal based on the digital intermediate frequency signal and the local carrier signal; the local complex sampled baseband signal and the local pseudocode sequence are coherently integrated to obtain the coherent integration result of the I / Q branch of the correlator group.

16. The system according to claim 15, characterized in that, The correlator group obtains the coherent integral result of the I / Q branch according to the following equation (5): in, Indicates the current sampling time. It is a digital intermediate frequency signal. For the local carrier NCO phase, For the first The local pseudocode sequence corresponding to the path correlator, For the coherent integration time, and The first The coherent integral results of the in-phase and quadrature branches of the path correlator For complex correlation output, This represents the total number of correlators.

17. The system according to claim 1 or 15, characterized in that, The correlator group includes: a first multiplier, multiple second multipliers, multiple summers, and multiple modular square operators, wherein the number of second multipliers, summers, and modular square operators are equal and correspond one-to-one; The first multiplier receives the digital intermediate frequency signal and the local carrier signal, performs a multiplication operation on the digital intermediate frequency signal and the local carrier signal to obtain a local complex sampled baseband signal, and provides the local complex sampled baseband signal to the second multiplier; The second multiplier performs a multiplication operation on the local complex sampled baseband signal and the local pseudocode sequence to obtain a first operation result, and provides the first operation result to the corresponding summer; The summer performs a summation operation on the first operation result to obtain a second operation result, and provides the second operation result to the corresponding modulo square operator; The modular square operator performs a square operation on the second operation result to obtain the coherent integral result.

18. The system according to claim 1, characterized in that, The baseband signal processing unit also includes a peak value determination module; Each correlator group provides the coherent integration result of the I / Q branch of the correlator group module to the peak value determination module; The peak value determination module receives the coherent integration results of the I / Q branches of each correlator group, calculates the signal strength of each coherent integration result, and provides the coherent integration result with the largest signal strength to the open-loop tracking control module.

19. The system according to claim 18, characterized in that, The peak value determination module calculates the signal strength of the coherent integral result according to the following formula (6): （6） This represents the coherent integral result with the highest signal strength. This represents the number of correlator groups.

20. A GNSS occultation signal tracking method, characterized in that, The method is applied to the GNSS occultation signal tracking system according to any one of claims 1-19, the system including a control unit and a baseband signal processing unit, the baseband signal processing unit including a multiple correlator module, the multiple correlator module including multiple correlator groups, the chip interval width of the multiple correlator groups being different or the same; The method includes: In response to determining the existence of a GNSS atmospheric occultation event, the control unit calculates the first frequency and the first pseudorange corresponding to the GNSS satellite in the occultation state, and provides the first frequency and the first pseudorange as tracking guidance parameters to the baseband signal processing unit. The baseband signal processing unit receives the digital intermediate frequency signal transmitted by the occultation radio frequency unit; generates a local carrier signal according to the first frequency, generates a local pseudocode sequence according to the first pseudorange and the chip spacing width of the multiple correlator groups, and provides the digital intermediate frequency signal, the local carrier signal and the local pseudocode sequence to the multiple correlator groups; the code phases of the local pseudocode sequences are different. Each correlator group performs coherent integration based on the digital intermediate frequency signal, the local carrier signal, and the local pseudocode sequence to obtain the coherent integration result of the I / Q branch of the correlator group; The baseband signal processing unit provides the control unit with the coherent integration result with the highest signal strength among the coherent integration results of the multiple correlator groups.

21. An electronic device, characterized in that, It includes a processor and a field-programmable gate array (FPGA), the processor including a control unit as described in any one of claims 1-19, and the FPGA including a baseband signal processing unit as described in any one of claims 1-19.

22. A readable storage medium, characterized in that, A program or instructions are stored on the readable storage medium, which, when executed by a processor, implement the method of claim 20.

Images