A method and system for processing full-code interferometric signals of multi-standard GNSS on-board satellites

Abstract

This application provides a method and system for processing full-code interferometric signals in spaceborne multi-standard GNSS, relating to the field of GNSS measurement. This method combines three detection methods for synchronous detection. Interferometric processing is performed based on the direct and reflected fundamental frequency signals. The reflected fundamental frequency signal is correlated with a local code to obtain a wide range of delay information through local code DDM tracking, which assists in interferometric tracking, enabling accurate capture of reflected navigation signals in interferometric measurements. Carrier phase tracking processing is performed based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code. This utilizes the accurate delay information of the interferometric measurement data to assist carrier phase tracking, allowing stable raw carrier phase measurement data to be obtained. Thus, by using data assistance between different detection methods, the shortcomings of each method are compensated for, improving the detection capability of reflected signals.

Description

Technical Field

[0001] This application relates to the field of GNSS measurement technology, and in particular to a method and system for processing spaceborne multi-standard GNSS full-code interferometric signals. Background Technology

[0002] With the continuous improvement of China's BeiDou and Global Navigation Satellite System (GNSS), its application areas have expanded from the initial navigation and positioning to the detection of atmospheric and meteorological elements on a global scale, as well as the inversion of parameters such as sea surface wind speed, sea surface height, sea ice, soil moisture, and vegetation.

[0003] Traditional GNSS reflection signal processing technology uses local known codes to perform correlation operations with the probe signal, and then obtains measurement information such as signal delay and phase from the correlation results. This scheme is widely used because it is relatively simple in design and has a certain ability to capture weak signals.

[0004] However, in addition to publicly available code patterns (e.g., coarse acquisition codes), navigation signal frequency bands often contain military codes or encryption codes with wider bandwidth and higher signal energy. Because the precise code structure of these military codes is encrypted and cannot be publicly obtained, traditional technologies cannot utilize these signal resources for related processing, resulting in insufficient measurement accuracy. Summary of the Invention

[0005] In view of the above problems, embodiments of this application provide a method and system for processing spaceborne multi-standard GNSS full-code interferometric signals, so as to overcome the above problems or at least partially solve the above problems.

[0006] A first aspect of this application discloses a method for processing spaceborne multi-standard GNSS full-code interferometric signals, the method comprising:

[0007] By receiving the first direct navigation signal through the positioning antenna, it is determined whether the navigation satellite meets the conditions for reflection observation of the target area;

[0008] When the navigation satellite meets the conditions for reflection observation of the target area, it receives a second direct navigation signal through a direct antenna and a first reflected navigation signal through a reflective antenna.

[0009] The second direct navigation signal is down-converted to a direct baseband signal, and the first reflected navigation signal is down-converted to a reflected baseband signal;

[0010] The reflected fundamental frequency signal and the local code are correlated to generate local code delay Doppler map (DDM) data.

[0011] Interference processing is performed on the direct fundamental frequency signal and the reflected fundamental frequency signal to obtain interferometric measurement data, and the delay information of the interferometric measurement data is determined.

[0012] Based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code, carrier phase tracking processing is performed to obtain the original carrier phase measurement data;

[0013] The interferometric measurement data, local code DDM data, and the original carrier phase measurement data are sent to the ground inversion center so that the ground inversion center can invert the surface parameters of the target area.

[0014] Optionally, by receiving the first direct navigation signal through the positioning antenna, it is determined whether the navigation satellite meets the conditions for reflection observation of the target area, including:

[0015] Calculate the positions of navigation satellites and low-Earth orbit satellites based on the first direct navigation signal;

[0016] The location of the mirror reflection point is determined based on the positions of the navigation satellites and the low-orbit satellites.

[0017] If the line connecting the location of the mirror reflection point and the location of the low-orbit satellite is outside the coverage area of ​​the reflecting antenna, it is determined that the navigation satellite does not meet the reflection observation conditions for the target area.

[0018] If the line connecting the mirror reflection point and the low-orbit satellite is within the coverage area of ​​the reflecting antenna, then the navigation satellite meets the reflection observation conditions for the target area.

[0019] Optionally, the method further includes:

[0020] When the navigation satellite meets the reflection observation conditions for the target area, control information is calculated based on the first direct navigation signal, and the control information includes at least a local code control word.

[0021] The local code is generated based on the local code control word.

[0022] Optionally, the control information further includes: a direct navigation signal down-conversion control word; down-converting the second direct navigation signal to a direct baseband signal, including:

[0023] The second direct navigation signal is processed into a medium-frequency digital direct signal;

[0024] Calculate the Doppler frequency of the direct navigation signal based on the down-conversion control word of the direct navigation signal;

[0025] Based on the calculated Doppler frequency of the direct navigation signal, the intermediate frequency digital direct signal is down-converted to obtain the direct base frequency signal.

[0026] Optionally, the control information further includes: a down-conversion control word for the reflected navigation signal; down-converting the first reflected navigation signal to a reflected baseband signal, including:

[0027] The first reflected navigation signal is processed into a medium-frequency digital reflected signal;

[0028] Calculate the Doppler frequency of the reflected navigation signal based on the down-conversion control word of the reflected navigation signal;

[0029] Based on the calculated Doppler frequency of the reflected navigation signal, the intermediate frequency digital reflected signal is down-converted to obtain the reflected fundamental frequency signal.

[0030] Optionally, the control information further includes: a direct signal delay control word;

[0031] The method further includes:

[0032] Determine the delay information of the local code DDM data;

[0033] Interference processing is performed on the direct fundamental frequency signal and the reflected fundamental frequency signal to obtain interferometric measurement data, including:

[0034] According to the direct signal delay control word, the direct baseband signal is delayed to obtain a first delayed direct baseband signal;

[0035] Initial interferometric measurement data are obtained by interferometric correlation and integral accumulation between the first delayed direct fundamental frequency signal and the reflected fundamental frequency signal;

[0036] The initial interferometric measurement data is adjusted based on the delay information of the local code DDM data to obtain the interferometric measurement data.

[0037] Optionally, the initial interferometric data is adjusted based on the delay information of the local code DDM data to obtain the interferometric data, including:

[0038] The delay amount of the direct fundamental frequency signal is determined based on the delay information of the local code DDM data and the initial interferometric measurement data.

[0039] Based on the delay amount of the direct baseband signal, the direct baseband signal is delayed to obtain a second delayed direct baseband signal;

[0040] The adjusted interferometric measurement data are obtained by interferometric correlation and integral accumulation between the second delayed direct fundamental frequency signal and the reflected fundamental frequency signal.

[0041] Optionally, carrier phase tracking processing is performed based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code to obtain raw carrier phase measurement data, including:

[0042] Carrier phase tracking calculations are performed based on the reflected fundamental frequency signal and the local code to obtain preliminary carrier phase raw measurement data.

[0043] Based on the delay information of the interferometric measurement data, the preliminary carrier phase original measurement data is corrected to obtain the carrier phase original measurement data.

[0044] Optionally, the local code control word is determined based on the local code nominal rate and clock frequency.

[0045] Optionally, the down-conversion control word of the direct navigation signal is calculated according to the following steps:

[0046] When the navigation satellite meets the conditions for reflection observation of the target area, the measured Doppler frequency of the direct navigation signal is obtained based on the first direct navigation signal;

[0047] The down-conversion control word of the direct navigation signal is calculated based on the measured Doppler frequency of the direct navigation signal, the nominal center frequency of the intermediate frequency of the second direct navigation signal and the first reflected navigation signal, and the clock frequency.

[0048] Optionally, the down-conversion control word for the reflected navigation signal is calculated according to the following steps:

[0049] Calculate the Doppler frequency of the observed reflected navigation signal based on the velocity of the mirror reflection point, the velocity of the navigation satellite, and the velocity of the low-Earth orbit satellite;

[0050] The down-conversion control word of the reflected navigation signal is calculated based on the observed Doppler frequency of the reflected navigation signal, the nominal center frequency of the intermediate frequency of the second direct navigation signal and the first reflected navigation signal, and the clock frequency.

[0051] Optionally, the direct signal delay control word is determined based on the geometric distance of the second direct navigation signal and the geometric distance of the first reflected navigation signal.

[0052] A second aspect of this application discloses a spaceborne multi-standard GNSS full-code interferometric signal processing system. The system includes a control unit and a baseband signal processing unit. The baseband signal processing unit includes: a down-conversion control unit, an interferometric processing unit, a local code DDM tracking unit, a carrier phase tracking unit, and a data transmission unit, wherein:

[0053] The control unit receives the first direct navigation signal through the positioning antenna and determines whether the navigation satellite meets the reflection observation conditions of the target area.

[0054] When the navigation satellite meets the conditions for reflection observation of the target area, the baseband signal processing unit receives a second direct navigation signal through a direct antenna and a first reflected navigation signal through a reflective antenna.

[0055] The downconversion control unit downconverts the second direct navigation signal to a direct baseband signal, and downconverts the first reflected navigation signal to a reflected baseband signal;

[0056] The local code DDM tracking unit correlates the reflected fundamental frequency signal with the local code to generate local code DDM data.

[0057] The interference processing unit performs interference processing on the direct fundamental frequency signal and the reflected fundamental frequency signal to obtain interference measurement data and determine the delay information of the interference measurement data;

[0058] The carrier phase tracking unit performs carrier phase tracking processing based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code to obtain the original carrier phase measurement data;

[0059] The data transmission unit sends the interferometric measurement data, the local code DDM data, and the carrier phase raw measurement data to the ground inversion center so that the ground inversion center can invert the surface parameters of the target area.

[0060] Optionally, the system further includes a first radio frequency front-end unit and a first digital-to-analog converter (A / D) sampling unit, and the baseband signal processing unit further includes a local code generator;

[0061] The first radio frequency front-end unit amplifies, filters, and down-converts the first direct navigation signal to obtain the first direct analog signal;

[0062] The first A / D sampling unit samples the first direct analog signal to obtain the first digital signal;

[0063] The control unit calculates control information based on the first digital signal, and the control information includes at least a local code control word.

[0064] The local code generator generates the local code based on the local code control word.

[0065] Optionally, the control information further includes a direct navigation signal down-conversion control word; the system further includes a second radio frequency front-end unit and a second A / D sampling unit; the baseband signal processing unit further includes: a first signal filtering unit, a direct down-conversion unit, a phase compensation unit, and a down-conversion control unit;

[0066] The second radio frequency front-end unit amplifies, filters, and down-converts the second direct navigation signal to obtain the second direct analog signal;

[0067] The second A / D sampling unit samples the second direct analog signal to obtain the second digital signal;

[0068] The first signal filtering unit filters the second digital signal to obtain an intermediate frequency digital direct signal;

[0069] The down-conversion control unit and the phase compensation unit calculate the Doppler frequency of the direct navigation signal based on the down-conversion control word of the direct navigation signal;

[0070] The direct downconversion unit performs downconversion processing on the intermediate frequency digital direct signal based on the calculated Doppler frequency of the direct navigation signal to obtain the direct base frequency signal.

[0071] Optionally, the control information further includes a down-conversion control word for the reflected navigation signal; the system further includes a third A / D sampling unit; the baseband signal processing unit further includes: a reflected down-conversion unit and a second signal filtering unit;

[0072] The second radio frequency front-end unit amplifies, filters, and downconverts the first reflected navigation signal to obtain the first reflected analog signal;

[0073] The second A / D sampling unit samples the first reflected analog signal to obtain the third digital signal;

[0074] The second signal filtering unit filters the third digital signal to obtain an intermediate frequency digital reflection signal;

[0075] The down-conversion control unit calculates the Doppler frequency of the reflected navigation signal based on the down-conversion control word of the reflected navigation signal;

[0076] The reflection down-conversion unit performs down-conversion processing on the intermediate frequency digital reflection signal according to the calculated Doppler frequency of the reflected navigation signal to obtain the reflected fundamental frequency signal.

[0077] Optionally, the interference processing unit includes: a delay control unit and an interference-related signal processing unit;

[0078] The delay control unit performs delay processing on the direct baseband signal according to the direct signal delay control word to obtain the first delayed direct baseband signal;

[0079] The interference correlation signal processing unit performs interference correlation and integral accumulation between the first delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain initial interference measurement data; and adjusts the initial interference measurement data according to the delay information of the local code DDM data to obtain the interference measurement data.

[0080] Optionally, the delay control unit determines the direct baseband signal delay based on the delay information of the local code DDM data and the initial interferometric measurement data; and performs delay processing on the direct baseband signal based on the direct baseband signal delay to obtain a second delayed direct baseband signal;

[0081] The interference correlation signal processing unit performs interference correlation and integral accumulation on the second delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain the adjusted interference measurement data.

[0082] Optionally, the baseband signal processing unit is deployed in a field-programmable gate array (FPGA) chip.

[0083] Optionally, the spaceborne multi-standard GNSS full-code interferometric signal processing system is deployed on a low-Earth orbit satellite.

[0084] The embodiments of this application have the following advantages:

[0085] In this embodiment, three detection methods are combined to simultaneously detect the same target area. Interference processing is performed based on the direct and reflected baseband signals. The reflected baseband signal is correlated with the local code to obtain a wide range of delay information through local code DDM tracking, which assists in interferometric tracking. This overcomes the narrow delay range problem of interferometric tracking methods, enabling accurate capture of reflected navigation signals in interferometric measurements. Carrier phase tracking processing is performed based on the delay information of the interferometric measurement data, the reflected baseband signal, and the local code. The accurate delay information of the interferometric measurement data assists carrier tracking, allowing stable raw carrier phase measurement data to be obtained. Therefore, data assistance between different detection methods compensates for the shortcomings of each method, improving the detection capability of reflected signals.

[0086] Furthermore, the method in this embodiment performs interferometric processing based on the direct baseband signal and the reflected baseband signal, utilizing all code patterns (i.e., military and civilian codes) within the navigation signal frequency band. This results in a wide available signal bandwidth, leading to higher resolution of the acquired measurement data and significantly improved measurement accuracy compared to traditional GNSS reflection signal processing techniques. In addition, the method in this embodiment processes data synchronously by receiving the direct navigation signal and the reflected navigation signal, and outputs interferometric measurement data, local code DDM data, and raw carrier phase measurement data in real time. Compared to traditional spaceborne measurement techniques, this method offers higher data timeliness.

[0087] Thus, the method of this application embodiment realizes real-time tracking of direct navigation signals and reflected navigation signals across the entire frequency band and multiple standards. The final output detection data is used for surface parameter inversion of the target area, solving the problem of high bandwidth and high measurement accuracy that traditional GNSS reflection signal processing technology cannot achieve, and improving the accuracy of global surface parameter measurement. Attached Figure Description

[0088] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0089] Figure 1 This is a flowchart illustrating the steps of a spaceborne multi-standard GNSS full-code interferometric signal processing method provided in an embodiment of this application.

[0090] Figure 2 This is a flowchart of a method for processing full-code interferometric signals of multi-standard GNSS on a spaceborne network, provided in an embodiment of this application.

[0091] Figure 3 This is a schematic diagram of a spaceborne multi-standard GNSS full-code interferometric signal processing system provided in an embodiment of this application. Detailed Implementation

[0092] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the technical solutions in 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 in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0093] The relevant technologies mainly include three GNSS signal processing techniques: traditional GNSS reflection signal processing, GNSS interferometry, and carrier phase tracking. Traditional GNSS reflection signal processing uses local codes to correlate with reflected navigation signals to obtain tracking results, and finally retrieves the detected element based on the tracking results. However, this method cannot utilize all code patterns for correlation processing, resulting in insufficient measurement accuracy. GNSS interferometry uses direct navigation signals to perform interferometric correlation with reflected signals to obtain reflection signal tracking results. All code patterns within the navigation signal frequency band can be utilized. Although this technology has the advantages of high bandwidth and high precision, its delay range is narrow. Carrier phase tracking measures the phase difference of the carrier based on the reflected navigation signal and local codes. This method has high phase measurement accuracy, but it requires accurate signal delay to achieve stable phase tracking.

[0094] Furthermore, existing spaceborne GNSS interferometry equipment employs a software-defined approach, directly acquiring raw direct and reflected GNSS navigation digital intermediate frequency signals, which are then transmitted from the satellite to the ground for data processing. The advantage of this approach is its flexible configuration, allowing for different ground-based data processing techniques. However, this method requires significant storage space to store the raw data, and the satellite must possess sufficient data bandwidth to transmit the raw acquired data to the ground in real time.

[0095] To overcome the limitations of related technologies, this application provides a spaceborne multi-standard GNSS full-code interferometric signal processing method and system. By combining interferometry, local code DDM and carrier phase detection methods to simultaneously observe the same target area, the resulting measurement data assist each other, greatly improving the reflection detection capability.

[0096] This application provides a method for processing multi-standard GNSS full-code interferometric signals on a spaceborne platform. This method can be implemented using a multi-standard GNSS full-code interferometric signal processing system deployed on a low-Earth orbit satellite. (Refer to...) Figure 1 As shown, Figure 1 This is a flowchart illustrating the steps of a spaceborne multi-standard GNSS full-code interferometric signal processing method provided in an embodiment of this application. Figure 1 As shown, the spaceborne multi-standard GNSS full-code interferometric signal processing method may include steps S110 to S170:

[0097] Step S110: Receive the first direct navigation signal through the positioning antenna to determine whether the navigation satellite meets the reflection observation conditions for the target area.

[0098] The first direct navigation signal refers to the direct navigation signal (i.e., GNSS navigation signal) directly transmitted by the navigation satellite (without reflection from the target area) and received by the positioning antenna. Based on the first direct navigation signal received by the positioning antenna, functions such as positioning calculation and time maintenance can be performed to determine whether the navigation satellite meets the reflection observation conditions for the target area.

[0099] Whether a navigation satellite meets the conditions for reflection observation of a target area can be understood as whether the direction of the reflected navigation signal of the direct navigation signal sent by the navigation satellite in the target area is within the coverage area of ​​the reflecting antenna. Only when the navigation satellite meets the conditions for reflection observation of the target area can the reflecting antenna receive the corresponding reflected navigation signal.

[0100] It is understandable that the aforementioned navigation satellites could be China's BeiDou navigation satellites, the United States' GPS (Global Positioning System) navigation satellites, Europe's Galileo navigation satellites, and Russia's GLONASS (GLONASS is Russian for Global Navigation Satellite System) navigation satellites, etc.

[0101] Step S120: When the navigation satellite meets the conditions for reflection observation of the target area, the second direct navigation signal is received through the direct antenna, and the first reflected navigation signal is received through the reflective antenna.

[0102] The second direct navigation signal refers to a direct navigation signal (i.e., a GNSS navigation signal) directly transmitted by a navigation satellite (without reflection from the target area) and received through a direct-view antenna. It can be understood that both the first and second direct navigation signals are direct navigation signals transmitted by navigation satellites; the difference lies in the antennas used for reception. Specifically, the direct navigation signal received through a positioning antenna is called the first direct navigation signal, and the direct navigation signal received through a direct-view antenna is called the second direct navigation signal.

[0103] The first reflected navigation signal refers to the reflected navigation signal obtained after the direct navigation signal emitted by the navigation satellite is reflected in the target area. Since the navigation satellite meets the reflection observation conditions of the target area, the direction of the first reflected navigation signal is within the coverage area of ​​the reflecting antenna, and therefore the first reflected navigation signal can be received through the reflecting antenna.

[0104] Step S130: Downconvert the second direct navigation signal to a direct baseband signal, and downconvert the first reflected navigation signal to a reflected baseband signal.

[0105] Step S140: Correlate the reflected fundamental frequency signal with the local code to generate local code delay Doppler map (DDM) data.

[0106] Among them, the local code DDM (Delay-Doppler Map) data is a two-dimensional (delay × Doppler) correlated power matrix that can reflect the energy distribution of the reflected navigation signal in the delay and Doppler frequency dimensions. The surface parameters of the target area can be inverted based on the generated local code DDM data (e.g., peak power, width, etc.).

[0107] The local code is a civilian code generated by a local code generator (such as the C / A code in GPS, where C / A code refers to the coarse acquisition code). The local code is a pseudo-random code sequence that does not contain navigation data bits or a carrier wave. By correlating the local code with the reflected baseband signal, the civilian code signal modulated in the reflected baseband signal can be captured, thus obtaining the corresponding measurement result, i.e., the local code DDM data. Correlating the reflected baseband signal and the local code involves performing correlation, coherence integration, and correlation power calculation on the two signals.

[0108] The local code DDM data has a wide delay range. The delay value and Doppler value in the local code DDM data can be used as delay information to assist in interferometric tracking (interferometry).

[0109] Step S150: Perform interferometric processing on the direct fundamental frequency signal and the reflected fundamental frequency signal to obtain interferometric measurement data, and determine the delay information of the interferometric measurement data.

[0110] Interference processing based on the direct fundamental frequency signal and the reflected fundamental frequency signal refers to: interferometric correlation between the direct fundamental frequency signal and the reflected fundamental frequency signal after delay control to form interferometric measurement waveform data.

[0111] Because it directly uses the fundamental frequency signal and the reflected fundamental frequency signal for interferometry processing, it does not need to know all the code patterns in the navigation signal frequency band, and it can also use the entire signal bandwidth in the navigation signal frequency band for interferometry measurement. Therefore, the obtained measurement data has higher resolution and high-precision interferometry measurement data is obtained.

[0112] In some embodiments, considering that the delay range of interferometric tracking is narrow and the delay range of local code DDM data is wide, the delay information of local code DDM data is used as auxiliary information and interferometrically processed together with the direct baseband signal and the reflected baseband signal, so that the reflected navigation signal can be accurately captured in the interferometric measurement.

[0113] Step S160: Perform carrier phase tracking processing based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code to obtain the original carrier phase measurement data.

[0114] Specifically, considering that carrier phase tracking requires accurate signal delay (e.g., phase delay amount), and interferometric data has precise delay information, the delay information of interferometric data is used to further assist carrier tracking. The delay information of interferometric data is combined with the reflected fundamental frequency signal and local code for carrier phase tracking processing, so that the carrier phase tracking method can obtain stable original carrier phase measurement data based on the accurate signal delay amount in the interferometric data.

[0115] Step S170: Send the interferometric measurement data, local code DDM data and the original carrier phase measurement data to the ground inversion center so that the ground inversion center can invert the surface parameters of the target area.

[0116] Interferometric data, local code DDM data, and raw carrier phase measurement data are sent to the ground inversion center as the final measurement data. The ground inversion center can then invert the surface parameters of the target area based on the interferometric data, local code DDM data, and raw carrier phase measurement data. For example, if the target area is the sea surface, sea surface height, sea surface wind speed, and wind direction can be inverted based on the interferometric data, local code DDM data, and raw carrier phase measurement data.

[0117] Since interferometric measurement data, local code DDM data, and carrier phase raw measurement data are simultaneous detections of the same target area using multiple detection methods, and the output data of different measurement results assist each other, the accurate surface parameters of the target area can be derived from the interferometric measurement data, local code DDM data, and carrier phase raw measurement data.

[0118] The technical solution of this application combines three detection methods to simultaneously detect the same target area. Interferometry is performed based on the direct and reflected fundamental frequency signals. The reflected fundamental frequency signal is correlated with a local code to obtain a wide range of delay information through local code DDM tracking, thus assisting in interferometric tracking. This overcomes the narrow delay range problem of traditional interferometric tracking methods, enabling accurate capture of reflected navigation signals in interferometry. The delay information from the interferometry data assists in carrier phase tracking, allowing for the acquisition of stable raw carrier phase measurement data. Therefore, by using data assistance between different detection methods, the shortcomings of each method are compensated for, improving the detection capability of reflected signals.

[0119] Furthermore, the method in this application embodiment performs interferometric processing based on the direct and reflected fundamental frequency signals, utilizing all code patterns within the navigation signal frequency band. This results in a wide available signal bandwidth, leading to higher resolution of the acquired measurement data and significantly improved measurement accuracy compared to traditional GNSS reflection signal processing techniques. In addition, the method in this application embodiment processes data synchronously by receiving the direct and reflected navigation signals, and outputs interferometric measurement data, local code DDM data, and raw carrier phase measurement data in real time. Compared to traditional spaceborne measurement techniques, this method offers higher data timeliness.

[0120] The following sections, 1.1, 1.2, and 1.3, provide a detailed description of the spaceborne multi-standard GNSS full-code interferometric signal processing method implemented in this application.

[0121] 1.1 Determine whether the conditions for reflection observation are met:

[0122] In an optional embodiment, step S110 above, "receiving the first direct navigation signal through the positioning antenna and determining whether the navigation satellite meets the reflection observation conditions for the target area," may specifically include sub-steps S110-1 to S110-4:

[0123] Step S110-1: Calculate the positions of navigation satellites and low-orbit satellites based on the first direct navigation signal;

[0124] Step S110-2: Determine the position of the mirror reflection point based on the position of the navigation satellite and the position of the low-orbit satellite;

[0125] Step S110-3: If the line connecting the mirror reflection point and the low-orbit satellite is outside the coverage area of ​​the reflecting antenna, it is determined that the navigation satellite does not meet the reflection observation conditions for the target area.

[0126] Step S110-4: If the line connecting the mirror reflection point and the low-orbit satellite is within the coverage area of ​​the reflecting antenna, then the navigation satellite meets the reflection observation conditions for the target area.

[0127] In this embodiment, the first direct navigation signal received by the positioning antenna is parsed according to the navigation satellite's interface control document to determine the navigation satellite's position and calculate the low-Earth orbit satellite's position. The interface control document refers to the technical specification document officially released by the BeiDou system or other GNSS systems, used to define the characteristics and parameters of the navigation satellite signal interface.

[0128] The location of the mirror reflection point is determined based on the positions of the navigation satellite and the low-Earth orbit (LEO) satellite. The mirror reflection point refers to the coordinates of the reflection point where the direct navigation signal transmitted by the navigation satellite reaches the LEO satellite via the shortest path after reflection from the Earth. The direct navigation signal transmitted by the navigation satellite forms a reflected navigation signal after passing the mirror reflection point. The direction of the line connecting the mirror reflection point and the LEO satellite position is the direction of the reflected navigation signal. When the direction of the line connecting the mirror reflection point and the LEO satellite position is outside the coverage area of ​​the reflecting antenna, it indicates that the direction of the reflected navigation signal is outside the coverage area of ​​the reflecting antenna, and the reflecting antenna cannot receive the reflected navigation signal outside its coverage area. In this case, it is determined that the navigation satellite does not meet the conditions for reflection observation of the target area. When the direction of the line connecting the mirror reflection point and the LEO satellite position is within the coverage area of ​​the reflecting antenna, it indicates that the direction of the reflected navigation signal is within the coverage area of ​​the reflecting antenna, and the reflecting antenna can receive the reflected navigation signal within its coverage area. In this case, it is determined that the navigation satellite meets the conditions for reflection observation of the target area.

[0129] The technical solution of this application embodiment determines whether the navigation satellite meets the reflection observation conditions of the target area based on the first direct navigation signal received by the positioning antenna, thereby realizing global control of signal processing. Only when the navigation satellite meets the reflection observation conditions of the target area is the second direct navigation signal received by the direct antenna and the first reflection navigation signal received by the reflection antenna triggered, so as to realize the detection of the target area based on the second direct navigation signal and the first reflection navigation signal.

[0130] 1.2 Calculate control information:

[0131] In an optional embodiment, the method, in addition to the steps described above, further includes the following steps:

[0132] Step A1: If the navigation satellite meets the reflection observation conditions for the target area, calculate the control information based on the first direct navigation signal, wherein the control information includes at least the local code control word;

[0133] Step A2: Generate the local code based on the local code control word.

[0134] In this embodiment, control information is used to control the processing of the second direct navigation signal and the first reflected navigation signal. When the navigation satellite meets the reflection observation conditions for the target area, control information is calculated based on the first direct navigation information to control the signal processing process. The control information includes at least a local control word, which is used by the local code generator to generate a local code, which is then correlated with the reflected fundamental frequency signal to generate local code DDM data.

[0135] Specifically, the local code control word is determined based on the local code nominal rate and clock frequency. For example, the local code control word... It can be represented as:

[0136]

[0137] in, Indicates the local code nominal rate. Indicates clock frequency. Indicates the maximum value of the control word.

[0138] In an optional embodiment, the control information further includes a direct navigation signal down-conversion control word, which is calculated according to the following steps:

[0139] Step B1: If the navigation satellite meets the reflection observation conditions for the target area, obtain the measured Doppler frequency of the direct navigation signal based on the first direct navigation signal;

[0140] Step B2: Calculate the down-conversion control word of the direct navigation signal based on the measured Doppler frequency of the direct navigation signal, the nominal center frequency of the intermediate frequency of the second direct navigation signal and the first reflected navigation signal, and the clock frequency.

[0141] In this embodiment, the direct navigation signal down-conversion control word can be used to control the second direct navigation signal to undergo down-conversion processing, that is, according to the direct navigation signal down-conversion control word, the second direct navigation signal is down-converted to a direct baseband signal. During the reception of the first direct navigation signal, the Doppler frequency of the direct navigation signal can be measured, and the direct navigation signal down-conversion control word can be calculated based on the measured Doppler frequency of the direct navigation signal.

[0142] For example, direct navigation signal downconversion control word It can be represented as:

[0143]

[0144] in, This indicates the measured Doppler frequency of the direct navigation signal. This indicates the nominal center frequency of the intermediate frequency between the second direct navigation signal and the first reflected navigation signal. This refers to the clock frequency, specifically the system clock frequency of the spaceborne multi-standard GNSS full-code interferometric signal processing system. Indicates the maximum value of the control word.

[0145] In an optional embodiment, the control information further includes a down-conversion control word for the reflected navigation signal, which is calculated according to the following steps:

[0146] Step C1: Calculate the Doppler frequency of the observed reflected navigation signal based on the velocity of the mirror reflection point, the velocity of the navigation satellite, and the velocity of the low-Earth orbit satellite;

[0147] Step C2: Calculate the down-conversion control word of the reflected navigation signal based on the observed Doppler frequency of the reflected navigation signal, the nominal center frequency of the intermediate frequency of the second direct navigation signal and the first reflected navigation signal, and the clock frequency.

[0148] In this embodiment of the application, the down-conversion control word for the reflected navigation signal can be used to control the first reflected navigation signal to undergo down-conversion processing, that is, according to the down-conversion control word for the reflected navigation signal, the first reflected navigation signal is down-converted into a reflected base frequency signal.

[0149] The Doppler frequency of the observed reflected navigation signal is calculated based on the velocity of the mirror reflection point, the velocity of the navigation satellite, and the velocity of the low-orbit satellite. This can be understood as calculating the Doppler frequency of the observed reflected navigation signal based on the velocity change of the mirror reflection point relative to the direct navigation signal.

[0150] Specifically, the Doppler frequency of the mirror reflection point relative to the navigation satellite is calculated based on the velocity of the mirror reflection point, the velocity of the navigation satellite, and the wavelength of the navigation signal. The Doppler frequency of the low-Earth orbit satellite relative to the mirror reflection point is calculated based on the velocity of the mirror reflection point, the velocity of the low-Earth orbit satellite, and the wavelength of the navigation signal. Thus, the Doppler frequency of the observed reflected navigation signal is obtained based on the Doppler frequency of the mirror reflection point relative to the navigation satellite and the Doppler frequency of the low-Earth orbit satellite relative to the mirror reflection point.

[0151] For example, the specular reflection point relative to the Doppler frequency of the navigation satellite It can be represented as:

[0152]

[0153] Low-Earth orbit satellite relative to the Doppler frequency of the mirror reflection point It can be represented as:

[0154]

[0155] Observe the Doppler frequency of the reflected navigation signal It can be represented as:

[0156]

[0157] in, Indicates the velocity of the point of reflection on the mirror. Indicates the speed of navigation satellites. Indicates the speed of low-Earth orbit satellites. Indicates the wavelength of the navigation signal.

[0158] Finally, the down-conversion control word of the reflected navigation signal can be calculated based on the observed Doppler frequency of the reflected navigation signal. For example, the down-conversion control word of the reflected navigation signal... It can be represented as:

[0159]

[0160] in, Indicates the Doppler frequency of the observed reflected navigation signal. This indicates the nominal center frequency of the intermediate frequency between the second direct navigation signal and the first reflected navigation signal. This refers to the clock frequency, specifically the system clock frequency of the spaceborne multi-standard GNSS full-code interferometric signal processing system. Indicates the maximum value of the control word.

[0161] In an optional embodiment, the control information further includes a direct signal delay control word; the direct signal delay control word is determined based on the geometric distance of the second direct navigation signal and the geometric distance of the first reflected navigation signal.

[0162] The direct signal delay control word is used to delay the direct baseband signal in order to align the direct baseband signal with the reflected baseband signal.

[0163] For example, direct signal delay control word It can be represented as:

[0164]

[0165] in, Indicates the geometric distance to the second direct navigation signal. This indicates that the geometric distance of the first reflected navigation signal has been determined. Represents the speed of light. Indicates the clock frequency.

[0166] By adopting the technical solution of this application embodiment, under the condition that the navigation satellite meets the reflection observation of the target area, control information (e.g., local code control word, direct navigation signal down-conversion control word, reflected navigation signal down-conversion control word, direct signal delay control word) is calculated based on the first direct navigation information, thereby realizing the control of the signal processing process based on the control information to ensure that accurate measurement results are obtained.

[0167] 1.3 Navigation signal processing procedure:

[0168] In an optional embodiment, the control information further includes: a direct navigation signal down-conversion control word; the step S130 above, "down-converting the second direct navigation signal to a direct baseband signal," may specifically include sub-steps S130-1 to S130-3:

[0169] Step S130-1: Process the second direct navigation signal into an intermediate frequency digital direct signal;

[0170] Step S130-2: Calculate the Doppler frequency of the direct navigation signal based on the down-conversion control word of the direct navigation signal;

[0171] Step S130-3: Based on the calculated Doppler frequency of the direct navigation signal, perform down-conversion processing on the intermediate frequency digital direct signal to obtain the direct base frequency signal.

[0172] In this embodiment of the application, after receiving the second direct navigation signal through the direct antenna, step S130-1 is first executed to process the second direct navigation signal into an intermediate frequency digital direct signal. That is, the second direct navigation signal is amplified, filtered and down-converted to obtain a second direct analog signal, and the second direct analog signal is sampled to obtain a second digital signal. The second digital signal is then filtered to obtain an intermediate frequency digital direct signal.

[0173] Next, step S130-2 is executed, and the Doppler frequency of the direct navigation signal is calculated according to the down-conversion control word of the direct navigation signal. That is, the initial Doppler frequency of the direct navigation signal is calculated according to the down-conversion control word of the direct navigation signal, and phase compensation processing is performed to obtain the Doppler frequency of the direct navigation signal.

[0174] Then, step S130-3 is executed, and the intermediate frequency digital direct signal is down-converted according to the calculated Doppler frequency of the direct navigation signal. That is, the intermediate frequency digital direct signal is mixed to the base frequency according to the calculated Doppler frequency of the direct navigation signal to obtain the direct base frequency signal.

[0175] In this way, by using the direct navigation signal down-conversion control word, the second direct navigation signal is down-converted into a direct baseband signal, so that subsequent signal processing can be performed based on the direct baseband signal, thereby reducing the cost and power consumption of subsequent signal processing.

[0176] In an optional embodiment, the control information further includes: a down-conversion control word for the reflected navigation signal; the step S130 above, "down-converting the first reflected navigation signal to a reflected base frequency signal," may specifically include sub-steps S130-4 to S130-6:

[0177] Step S130-4: Process the first reflected navigation signal into an intermediate frequency digital reflected signal;

[0178] Step S130-5: Calculate the Doppler frequency of the reflected navigation signal based on the down-conversion control word of the reflected navigation signal;

[0179] Step S130-6: Based on the calculated Doppler frequency of the reflected navigation signal, perform down-conversion processing on the intermediate frequency digital reflected signal to obtain the reflected fundamental frequency signal.

[0180] In this embodiment of the application, after receiving the first reflected navigation signal through the reflective antenna, firstly, in step S130-4, the first reflected navigation signal is processed into an intermediate frequency digital reflected signal, that is, the first reflected navigation signal is amplified, filtered and down-converted to obtain a first reflected analog signal, and the first reflected analog signal is sampled to obtain a third digital signal, and the third digital signal is filtered to obtain an intermediate frequency digital reflected signal.

[0181] Next, steps S130-5 and S130-6 are executed. Based on the down-conversion control word of the reflected navigation signal, the Doppler frequency of the reflected navigation signal is calculated. Based on the calculated Doppler frequency of the reflected navigation signal, the intermediate frequency digital reflected signal is down-converted. That is, based on the calculated Doppler frequency of the reflected navigation signal, the intermediate frequency digital reflected signal is mixed to the fundamental frequency to obtain the reflected fundamental frequency signal.

[0182] In this way, by using the down-conversion control word of the reflected navigation signal, the first reflected navigation signal is down-converted into a reflected baseband signal, so that subsequent signal processing can be performed based on the reflected baseband signal, thereby reducing the cost and power consumption of subsequent signal processing.

[0183] In an optional embodiment, the control information further includes a direct signal delay control word; the method further includes: determining delay information of the local code DDM data.

[0184] In this embodiment, the local code DDM data has a wide delay range, and the delay value and Doppler value in the local code DDM data can be used as the delay information of the local code DDM data to assist in interferometric tracking (interferometric measurement).

[0185] Furthermore, the step S150 above, "performing interferometric processing based on the direct fundamental frequency signal and the reflected fundamental frequency signal to obtain interferometric measurement data," may specifically include sub-steps S150-1 to S150-3:

[0186] Step S150-1: According to the direct signal delay control word, perform delay processing on the direct baseband signal to obtain a first delayed direct baseband signal;

[0187] Step S150-2: Perform interferometric correlation and integral accumulation between the first delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain initial interferometric measurement data;

[0188] Step S150-3: Adjust the initial interferometric measurement data according to the delay information of the local code DDM data to obtain the interferometric measurement data.

[0189] In this embodiment, the direct baseband signal is delayed according to the direct signal delay control word to align the direct baseband signal with the reflected baseband signal to obtain a first delayed direct baseband signal. Then, based on the aligned first delayed direct baseband signal and the reflected baseband signal, interference correlation and integral accumulation can be performed to obtain initial interferometric measurement data.

[0190] Considering the narrow delay range of interferometric tracking and the wide delay range of local code DDM data, the delay information of local code DDM data is used as auxiliary information to adjust the initial interferometric measurement data, so that the reflected navigation signal can be accurately captured in the interferometric measurement to obtain accurate interferometric measurement data.

[0191] Specifically, adjusting the initial interferometric measurement data based on the delay information of the local code DDM data to obtain the interferometric measurement data includes: determining the direct fundamental frequency signal delay based on the delay information of the local code DDM data and the initial interferometric measurement data; performing delay processing on the direct fundamental frequency signal based on the direct fundamental frequency signal delay to obtain a second delayed direct fundamental frequency signal; and performing interferometric correlation and integral accumulation between the second delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain the adjusted interferometric measurement data.

[0192] In this embodiment, the second direct navigation signal and the first reflected navigation signal change in real time. During signal processing, the delay information of the local code DDM data and the initial interferometric measurement data are used to continuously adjust the delay amount of the direct baseband signal. The direct baseband signal is then delayed according to the delay amount to align it with the reflected baseband signal. This allows for interferometric correlation and integral accumulation based on the aligned second delayed direct baseband signal and the reflected baseband signal, thereby adjusting the interferometric measurement data.

[0193] Thus, by using the delay information of the local code DDM data to assist in interferometric tracking, the problem of narrow delay range in interferometric tracking methods is overcome, enabling the reflected navigation signal to be accurately captured in interferometric measurements. Furthermore, by performing interferometric processing based on the direct fundamental frequency signal and the reflected fundamental frequency signal, all code patterns within the navigation signal frequency band are utilized, resulting in a wide available signal bandwidth. Consequently, the acquired measurement data has higher resolution, and the measurement accuracy is significantly improved compared to traditional GNSS reflection signal processing techniques.

[0194] In an optional embodiment, step S160 above, "performing carrier phase tracking processing based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code to obtain the original carrier phase measurement data," may specifically include sub-steps S160-1 to S160-2:

[0195] Step S160-1: Perform carrier phase tracking calculation based on the reflected fundamental frequency signal and the local code to obtain preliminary carrier phase raw measurement data;

[0196] Step S160-2: Based on the delay information of the interferometric measurement data, correct the preliminary carrier phase original measurement data to obtain the carrier phase original measurement data.

[0197] In this embodiment, the delay information (e.g., phase delay) of the interferometric measurement data is used to correct the carrier phase tracking calculation results based on the reflected fundamental frequency signal and the local code, so as to achieve continuous carrier phase tracking and obtain stable original carrier phase measurement data.

[0198] The following describes the spaceborne multi-standard GNSS full-code interferometric signal processing method of this application with reference to a specific embodiment. Figure 2 As shown, Figure 2 This is a flowchart of a spaceborne multi-standard GNSS full-code interferometric signal processing method provided in an embodiment of this application. The spaceborne multi-standard GNSS full-code interferometric signal processing method may include the following steps D1 to D11:

[0199] Step D1: Receive the first direct navigation signal through the positioning antenna and perform positioning calculation and time maintenance.

[0200] Step D2: Determine whether the navigation satellite meets the conditions for reflection observation of the target area.

[0201] Specifically, based on the first direct navigation signal, the positions of the navigation satellite and the low-orbit satellite are calculated; based on the positions of the navigation satellite and the low-orbit satellite, the position of the specular reflection point is determined; if the direction of the line connecting the specular reflection point and the low-orbit satellite is outside the coverage area of ​​the reflecting antenna, it is determined that the navigation satellite does not meet the conditions for reflection observation of the target area; if the direction of the line connecting the specular reflection point and the low-orbit satellite is within the coverage area of ​​the reflecting antenna, it is determined that the navigation satellite meets the conditions for reflection observation of the target area.

[0202] Step D3: If the navigation satellite meets the conditions for reflection observation of the target area, calculate the control information based on the first direct navigation signal. The control information includes the local code control word, the direct navigation signal down-conversion control word, the reflected navigation signal down-conversion control word, and the direct signal delay control word.

[0203] Step D4: Receive the second direct navigation signal via the direct antenna, and receive the first reflected navigation signal via the reflective antenna.

[0204] Step D5: Generate the local code based on the local code control word.

[0205] Step D6: According to the direct navigation signal downconversion control word, downconvert the second direct navigation signal to a direct baseband signal; and according to the reflected navigation signal downconversion control word, downconvert the first reflected navigation signal to a reflected baseband signal.

[0206] The step of downconverting the second direct navigation signal into a direct baseband signal according to the downconversion control word of the direct navigation signal includes: processing the second direct navigation signal into an intermediate frequency digital direct signal; calculating the Doppler frequency of the direct navigation signal according to the downconversion control word of the direct navigation signal; and performing downconversion processing on the intermediate frequency digital direct signal according to the calculated Doppler frequency of the direct navigation signal to obtain the direct baseband signal.

[0207] The process of downconverting the first reflected navigation signal to a reflected fundamental frequency signal according to the downconversion control word of the reflected navigation signal includes: processing the first reflected navigation signal into an intermediate frequency digital reflected signal; calculating the Doppler frequency of the reflected navigation signal according to the downconversion control word of the reflected navigation signal; and performing downconversion processing on the intermediate frequency digital reflected signal according to the calculated Doppler frequency of the reflected navigation signal to obtain the reflected fundamental frequency signal.

[0208] Step D7: Correlate the reflected fundamental frequency signal and the local code to generate local code DDM data, and determine the delay information of the local code DDM data.

[0209] Step D8: According to the direct signal delay control word, the direct baseband signal is delayed to obtain the first delayed direct baseband signal.

[0210] Step D9: Perform interferometric correlation and integral accumulation between the first delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain initial interferometric measurement data. Adjust the initial interferometric measurement data according to the delay information of the local code DDM data to obtain the final interferometric measurement data.

[0211] The adjustment of the initial interferometric measurement data based on the delay information of the local code DDM data includes: determining the delay amount of the direct fundamental frequency signal based on the delay information of the local code DDM data and the initial interferometric measurement data; performing delay processing on the direct fundamental frequency signal based on the delay amount to obtain a second delayed direct fundamental frequency signal; and performing interferometric correlation and integral accumulation between the second delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain the adjusted interferometric measurement data.

[0212] Step D10: Perform carrier phase tracking processing based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code. That is, perform carrier phase tracking calculation based on the reflected fundamental frequency signal and the local code to obtain preliminary carrier phase original measurement data. Correct the preliminary carrier phase original measurement data based on the delay information of the interferometric measurement data to obtain the carrier phase original measurement data.

[0213] Step D11: Send the local code DDM data, interferometric measurement data, and carrier phase raw measurement data to the ground inversion center so that the ground inversion center can invert the surface parameters of the target area.

[0214] Through the above implementation process, the same target area is simultaneously detected by combining three detection methods, enabling real-time signal processing of direct navigation signals and reflected navigation signals. High-precision interferometric measurement data, local code DDM data, and carrier phase raw measurement data are then transmitted to the ground inversion center in real time to achieve high-precision inversion of the surface parameters of the target area.

[0215] This application also provides a spaceborne multi-standard GNSS full-code interferometric signal processing system, referencing... Figure 3 As shown, Figure 3 This is a schematic diagram of a spaceborne multi-standard GNSS full-code interferometric signal processing system provided in an embodiment of this application. Figure 3 As shown, the spaceborne multi-standard GNSS full-code interferometric signal processing system includes: a control unit and a baseband signal processing unit. The baseband signal processing unit includes: a down-conversion control unit, an interferometric processing unit, a local code DDM tracking unit, a carrier phase tracking unit, and a data transmission unit, wherein:

[0216] The control unit receives the first direct navigation signal through the positioning antenna and determines whether the navigation satellite meets the reflection observation conditions of the target area.

[0217] When the navigation satellite meets the conditions for reflection observation of the target area, the baseband signal processing unit receives a second direct navigation signal through a direct antenna and a first reflected navigation signal through a reflective antenna.

[0218] The downconversion control unit downconverts the second direct navigation signal to a direct baseband signal, and downconverts the first reflected navigation signal to a reflected baseband signal;

[0219] The local code DDM tracking unit correlates the reflected fundamental frequency signal with the local code to generate local code DDM data.

[0220] The interference processing unit performs interference processing on the direct fundamental frequency signal and the reflected fundamental frequency signal to obtain interference measurement data and determine the delay information of the interference measurement data;

[0221] The carrier phase tracking unit performs carrier phase tracking processing based on the reflected fundamental frequency signal, the delay information of the interferometric measurement data, and the local code to obtain the original carrier phase measurement data;

[0222] The data transmission unit sends the interferometric measurement data, the local code DDM data, and the carrier phase raw measurement data to the ground inversion center so that the ground inversion center can invert the surface parameters of the target area.

[0223] In this embodiment of the application, the control unit may be a CTU (Collect Transfer Unit) control unit, which is used to complete the global control of the entire signal processing process, and the baseband signal processing unit is used to realize the real-time processing of navigation signals.

[0224] Specifically, the control unit receives the first direct navigation signal through the positioning antenna to determine whether the navigation satellite meets the reflection observation conditions for the target area. If the navigation satellite meets the reflection observation conditions for the target area, the baseband signal processing unit is triggered to process the navigation signal in real time. That is, the baseband signal processing unit receives the second direct navigation signal through the direct antenna and the first reflected navigation signal through the reflection antenna. The second direct navigation signal and the first reflected navigation signal are processed using the down-conversion control unit, the interferometric processing unit, the local code DDM tracking unit, and the carrier phase tracking unit. Finally, the obtained interferometric measurement data, local code DDM data, and carrier phase raw measurement data are transmitted to the ground inversion center through the transmission unit.

[0225] Thus, through this spaceborne multi-standard GNSS full-code interferometric signal processing system, the system can achieve integrated observation of the same target area using three detection methods: interferometry, local code DDM, and carrier phase. Furthermore, it can provide data assistance based on the advantages and disadvantages of each observation method, thereby improving the detection capability of reflected signals.

[0226] Furthermore, by using interferometry, a technological leap from single-code tracking to full-code tracking of navigation signals is achieved. Both military and civilian codes within the navigation frequency band can be effectively utilized without needing to know the structure of each code type, thus achieving 100% utilization of the navigation signal bandwidth and effectively improving the resolution of interferometric waveforms. Compared with traditional local code tracking technology, this significantly improves measurement accuracy.

[0227] In one optional embodiment, the system further includes a first radio frequency front-end unit and a first digital-to-analog converter (A / D) sampling unit, and the baseband signal processing unit further includes a local code generator;

[0228] The first radio frequency front-end unit amplifies, filters, and down-converts the first direct navigation signal to obtain the first direct analog signal;

[0229] The first A / D sampling unit samples the first direct analog signal to obtain the first digital signal;

[0230] The control unit calculates control information based on the first digital signal, and the control information includes at least a local code control word.

[0231] The local code generator generates the local code based on the local code control word.

[0232] In this embodiment, the first direct navigation signal received by the positioning antenna is a high-frequency radio frequency satellite signal, which is costly and consumes a lot of power if processed directly. Therefore, to facilitate subsequent processing, the first radio frequency front-end unit and the first A / D (Analog to Digital) sampling unit are used to amplify, filter, down-convert, and sample the first direct navigation signal in sequence, converting it into a digital signal, so as to perform control information calculation based on the digital information.

[0233] In one optional embodiment, the control information further includes a direct navigation signal down-conversion control word; the system further includes a second radio frequency front-end unit and a second A / D sampling unit; the baseband signal processing unit further includes: a first signal filtering unit, a direct down-conversion unit, a phase compensation unit, and a down-conversion control unit;

[0234] The second radio frequency front-end unit amplifies, filters, and down-converts the second direct navigation signal to obtain the second direct analog signal;

[0235] The second A / D sampling unit samples the second direct analog signal to obtain the second digital signal;

[0236] The first signal filtering unit filters the second digital signal to obtain an intermediate frequency digital direct signal;

[0237] The down-conversion control unit and the phase compensation unit calculate the Doppler frequency of the direct navigation signal based on the down-conversion control word of the direct navigation signal;

[0238] The direct downconversion unit performs downconversion processing on the intermediate frequency digital direct signal based on the calculated Doppler frequency of the direct navigation signal to obtain the direct base frequency signal.

[0239] In this embodiment, the second direct navigation signal is downconverted into a direct baseband signal using a second RF front-end unit, a second A / D sampling unit, a first signal filtering unit, a direct downconversion unit, a phase compensation unit, and a downconversion control unit. This allows subsequent signal processing to be performed based on the direct baseband signal, reducing the cost and power consumption of subsequent signal processing.

[0240] In one optional embodiment, the control information further includes a down-conversion control word for the reflected navigation signal; the system further includes a third A / D sampling unit; and the baseband signal processing unit further includes a reflected down-conversion unit and a second signal filtering unit.

[0241] The second radio frequency front-end unit amplifies, filters, and downconverts the first reflected navigation signal to obtain the first reflected analog signal;

[0242] The second A / D sampling unit samples the first reflected analog signal to obtain the third digital signal;

[0243] The second signal filtering unit filters the third digital signal to obtain an intermediate frequency digital reflection signal;

[0244] The down-conversion control unit calculates the Doppler frequency of the reflected navigation signal based on the down-conversion control word of the reflected navigation signal;

[0245] The reflection down-conversion unit performs down-conversion processing on the intermediate frequency digital reflection signal according to the calculated Doppler frequency of the reflected navigation signal to obtain the reflected fundamental frequency signal.

[0246] In this embodiment, a third radio frequency front-end, a third A / D sampling unit, a second signal filtering unit, a reflection down-conversion unit, and a down-conversion control unit are used to down-convert the first reflected navigation signal into a reflected baseband signal, so that subsequent signal processing can be performed based on the reflected baseband signal, thereby reducing the cost and power consumption of subsequent signal processing.

[0247] In one optional embodiment, the interference processing unit includes: a delay control unit and an interference-related signal processing unit;

[0248] The delay control unit performs delay processing on the direct baseband signal according to the direct signal delay control word to obtain the first delayed direct baseband signal;

[0249] The interference correlation signal processing unit performs interference correlation and integral accumulation between the first delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain initial interference measurement data; and adjusts the initial interference measurement data according to the delay information of the local code DDM data to obtain the interference measurement data.

[0250] In this embodiment, the delay control unit performs delay processing on the direct baseband signal according to the direct signal delay control word to align the direct baseband signal with the reflected baseband signal to obtain a first delayed direct baseband signal. Thus, based on the aligned first delayed direct baseband signal and the reflected baseband signal, interference correlation and integral accumulation can be performed to obtain initial interferometric measurement data.

[0251] Considering the narrow delay range of interferometric tracking and the wide delay range of local code DDM data, the delay information of local code DDM data is used as auxiliary information to adjust the initial interferometric measurement data, so that the reflected navigation signal can be accurately captured in the interferometric measurement to obtain accurate interferometric measurement data.

[0252] Specifically, the delay control unit determines the direct fundamental frequency signal delay based on the delay information of the local code DDM data and the initial interferometric measurement data; and performs delay processing on the direct fundamental frequency signal based on the direct fundamental frequency signal delay to obtain a second delayed direct fundamental frequency signal; the interferometric correlation signal processing unit performs interferometric correlation and integral accumulation on the second delayed direct fundamental frequency signal and the reflected fundamental frequency signal to obtain adjusted interferometric measurement data.

[0253] In this embodiment, the second direct navigation signal and the first reflected navigation signal change in real time. During signal processing, the delay information of the local code DDM data and the initial interferometric measurement data are used to continuously adjust the delay amount of the direct baseband signal. The direct baseband signal is then delayed according to the delay amount to align it with the reflected baseband signal. This allows for interferometric correlation and integral accumulation based on the aligned second delayed direct baseband signal and the reflected baseband signal, thereby adjusting the interferometric measurement data.

[0254] Thus, by using the delay information of the local code DDM data to assist in interferometric tracking, the problem of narrow delay range in interferometric tracking methods is overcome, enabling the reflected navigation signal to be accurately captured in interferometric measurements. Furthermore, by performing interferometric processing based on the direct fundamental frequency signal and the reflected fundamental frequency signal, all code patterns within the navigation signal frequency band are utilized, resulting in a wide available signal bandwidth. Consequently, the acquired measurement data has higher resolution, and the measurement accuracy is significantly improved compared to traditional GNSS reflection signal processing techniques.

[0255] In one alternative embodiment, the baseband signal processing unit is deployed in a field-programmable gate array (FPGA) chip.

[0256] In this embodiment, the baseband signal processing unit is deployed in an FPGA (Field Programmable Gate Array) chip. The digital intermediate frequency signals of the second direct navigation signal and the first reflected navigation signal are all processed and output in real time in the FPGA, which saves a lot of memory resources and satellite data resources compared with traditional measurement intermediate frequency signal acquisition technology.

[0257] In one alternative embodiment, the spaceborne multi-standard GNSS full-code interferometric signal processing system is deployed on a low-Earth orbit satellite.

[0258] In this embodiment, the spaceborne multi-standard GNSS full-code interferometric signal processing system is deployed on a low-Earth orbit satellite. The received second direct navigation signal and first transmitted navigation signal can be down-converted, delayed, interferometrically correlated, and local code and carrier phase tracked on the satellite. The final measurement data (i.e., interferometric measurement data, local code DDM data and carrier phase raw measurement data) is output to the satellite. Compared with international spaceborne GNSS interferometric measurement equipment, it occupies less hardware logic resources and storage resources, and the amount of data transmitted is lower.

[0259] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0260] This application describes embodiments of methods and systems according to embodiments of this application with reference to flowchart illustrations and / or block diagrams. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1A device that provides the functions specified in one or more boxes.

[0261] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0262] Although preferred embodiments of the present application 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 the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0263] Finally, 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 terminal device 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 terminal device. 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 terminal device that includes said element.

[0264] The above provides a detailed description of a spaceborne multi-standard GNSS full-code interferometric signal processing method and system provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A space-borne multi-mode GNSS all-code interferometric signal processing method, characterized in that, The method comprises the following steps: receiving a first direct navigation signal through a positioning antenna to determine whether a navigation satellite meets a reflection observation condition for a target area; in the case that the navigation satellite meets the reflection observation condition for the target area, receiving a second direct navigation signal through a direct antenna and receiving a first reflected navigation signal through a reflection antenna; calculating control information according to the first direct navigation signal, wherein the control information at least comprises a local code control word and a direct signal delay control word; generating a local code according to the local code control word; down-converting the second direct navigation signal into a direct base frequency signal and down-converting the first reflected navigation signal into a reflected base frequency signal; correlating the reflected base frequency signal and the local code to generate local code delay Doppler map (DDM) data and determine delay information of the local code DDM data; performing interference processing on the direct base frequency signal and the reflected base frequency signal to obtain interference measurement data and determine delay information of the interference measurement data; wherein performing interference processing on the direct base frequency signal and the reflected base frequency signal to obtain interference measurement data comprises: performing delay processing on the direct base frequency signal according to the direct signal delay control word to obtain a first delayed direct base frequency signal; performing interference correlation and integration and accumulation on the first delayed direct base frequency signal and the reflected base frequency signal to obtain initial interference measurement data; adjusting the initial interference measurement data according to the delay information of the local code DDM data to obtain the interference measurement data; performing carrier phase tracking processing on the reflected base frequency signal, the delay information of the interference measurement data and the local code to obtain carrier phase raw measurement data; sending the interference measurement data, the local code DDM data and the carrier phase raw measurement data to a ground inversion center for the ground inversion center to perform inversion on surface parameters of the target area.

2. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 1, characterized in that, The method of determining whether a navigation satellite meets a reflection observation condition for a target area through a positioning antenna receiving a first direct navigation signal comprises the following steps: calculating a navigation satellite position and a low-orbit satellite position according to the first direct navigation signal; determining a mirror reflection point position according to the navigation satellite position and the low-orbit satellite position; in the case that a line direction of the mirror reflection point position and the low-orbit satellite position is located outside a coverage range of the reflection antenna, determining that the navigation satellite does not meet the reflection observation condition for the target area; in the case that the line direction of the mirror reflection point position and the low-orbit satellite position is located inside the coverage range of the reflection antenna, determining that the navigation satellite meets the reflection observation condition for the target area.

3. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 1, characterized in that, The control information further comprises a direct navigation signal down-conversion control word; and down-converting the second direct navigation signal into a direct base frequency signal comprises the following steps: processing the second direct navigation signal into an intermediate frequency digital direct signal; calculating a direct navigation signal Doppler frequency according to the direct navigation signal down-conversion control word; According to the calculated direct navigation signal Doppler frequency, the intermediate frequency digital direct signal is down-converted to obtain the direct baseband signal.

4. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 1, characterized in that, The control information further comprises: a reflected navigation signal down-conversion control word; and down-converting the first reflected navigation signal to a reflected baseband signal, comprising: processing the first reflected navigation signal into an intermediate frequency digital reflected signal; According to the reflected navigation signal down-conversion control word, the reflected navigation signal Doppler frequency is calculated; According to the calculated reflected navigation signal Doppler frequency, the intermediate frequency digital reflected signal is down-converted to obtain the reflected baseband signal.

5. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 1, characterized in that, According to the delay information of the local code DDM data, the initial interference measurement data is adjusted to obtain the interference measurement data, comprising: According to the delay information of the local code DDM data and the initial interference measurement data, the direct baseband signal delay amount is determined; According to the direct baseband signal delay amount, the direct baseband signal is delayed to obtain a second delayed direct baseband signal; According to the second delayed direct baseband signal and the reflected baseband signal, interference correlation and integral accumulation are performed to obtain adjusted interference measurement data.

6. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 1, wherein, According to the reflected baseband signal, the delay information of the interference measurement data, and the local code, carrier phase tracking processing is performed to obtain carrier phase raw measurement data, comprising: According to the reflected baseband signal and the local code, carrier phase tracking calculation is performed to obtain preliminary carrier phase raw measurement data; According to the delay information of the interference measurement data, the preliminary carrier phase raw measurement data is corrected to obtain the carrier phase raw measurement data.

7. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 1, wherein, The local code control word is determined according to the local code nominal rate and the clock frequency.

8. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 3, wherein, The direct navigation signal down-conversion control word is calculated according to the following steps: In the case that the navigation satellite satisfies the reflected observation condition for the target area, the measured direct navigation signal Doppler frequency is obtained according to the first direct navigation signal; According to the measured direct navigation signal Doppler frequency, the second direct navigation signal and the first reflected navigation signal intermediate frequency nominal center frequency, and the clock frequency, the direct navigation signal down-conversion control word is calculated.

9. The space-borne multi-mode GNSS all-code interferometric signal processing method according to claim 4, wherein, The reflected navigation signal down-conversion control word is calculated according to the following steps: According to the mirror reflection point velocity, the navigation satellite velocity and the low-orbit satellite velocity, the observed reflected navigation signal Doppler frequency is calculated; According to the observed reflected navigation signal Doppler frequency, the second direct navigation signal and the first reflected navigation signal intermediate frequency nominal center frequency, and the clock frequency, the reflected navigation signal down-conversion control word is calculated.

10. The space-borne multi-constellation GNSS all-code interferometric signal processing method according to claim 1, characterized in that, The direct signal delay control word is determined according to the geometric distance of the second direct navigation signal and the geometric distance of the first reflected navigation signal.

11. A space-borne multi-constellation GNSS all-code interferometric signal processing system, characterized in that, comprising: The first radio frequency front-end unit, the first digital-to-analog conversion A / D sampling unit, the control unit and the baseband signal processing unit, the baseband signal processing unit comprises: a down-conversion control unit, an interference processing unit, a local code DDM tracking unit, a carrier phase tracking unit, a data sending unit, a local code generator, wherein: The control unit receives a first direct navigation signal through a positioning antenna, and determines whether a navigation satellite satisfies a reflection observation condition for a target area; The baseband signal processing unit receives a second direct navigation signal through a direct antenna and a first reflected navigation signal through a reflected antenna when the navigation satellite satisfies the reflection observation condition for the target area; The first radio frequency front-end unit amplifies, filters and down-converts the first direct navigation signal to obtain a first direct analog signal; The first A / D sampling unit samples the first direct analog signal to obtain a first digital signal; The control unit calculates control information according to the first digital signal, and the control information at least comprises a local code control word and a direct signal delay control word; The local code generator generates a local code according to the local code control word; The down-conversion control unit down-converts the second direct navigation signal into a direct base frequency signal, and down-converts the first reflected navigation signal into a reflected base frequency signal; The local code DDM tracking unit correlates the reflected base frequency signal and a local code to generate local code DDM data; The interference processing unit performs interference processing on the direct base frequency signal, the reflected base frequency signal and delay information of the local code DDM data to obtain interference measurement data, and determines delay information of the interference measurement data; wherein the interference processing unit comprises a delay control unit and an interference correlation signal processing unit; the interference processing unit performs interference processing on the direct base frequency signal, the reflected base frequency signal and delay information of the local code DDM data to obtain interference measurement data, which comprises: the delay control unit delays the direct base frequency signal according to the direct signal delay control word to obtain a first delayed direct base frequency signal; the interference correlation signal processing unit performs interference correlation and integration accumulation on the first delayed direct base frequency signal and the reflected base frequency signal to obtain initial interference measurement data; and adjusts the initial interference measurement data according to the delay information of the local code DDM data to obtain the interference measurement data; The carrier phase tracking unit performs carrier phase tracking processing on the reflected base frequency signal, delay information of the interference measurement data and the local code to obtain carrier phase original measurement data; The data sending unit sends the interference measurement data, the local code DDM data and the carrier phase original measurement data to a ground inversion center, so that the ground inversion center inverts surface parameters of the target area.

12. The space-borne multi -mode GNSS all-code inter- signal processing system according to claim 11, characterized in that The control information further comprises a direct navigation signal down-conversion control word; the system further comprises a second radio frequency front-end unit and a second A / D sampling unit. The baseband signal processing unit further comprises a first signal filtering unit, a direct down-conversion unit, a phase compensation unit and a down-conversion control unit. The second radio frequency front-end unit amplifies, filters and down-converts the second direct navigation signal to obtain a second direct analog signal. The second A / D sampling unit samples the second direct analog signal to obtain a second digital signal. The first signal filtering unit filters the second digital signal to obtain an intermediate frequency digital direct signal. The down-conversion control unit and the phase compensation unit calculate a direct navigation signal Doppler frequency according to a direct navigation signal down-conversion control word. The direct down-conversion unit down-converts the intermediate frequency digital direct signal according to the calculated direct navigation signal Doppler frequency to obtain the direct base frequency signal.

13. The space-borne multi -mode GNSS all-code inter- signal processing system according to claim 12, characterized in that The control information further comprises a reflected navigation signal down-conversion control word; and the system further comprises a third A / D sampling unit. The baseband signal processing unit further comprises a reflected down-conversion unit and a second signal filtering unit. The second radio frequency front-end unit amplifies, filters and down-converts the first reflected navigation signal to obtain a first reflected analog signal. The second A / D sampling unit samples the first reflected analog signal to obtain a third digital signal. The second signal filtering unit filters the third digital signal to obtain an intermediate frequency digital reflected signal. The down-conversion control unit calculates a reflected navigation signal Doppler frequency according to the reflected navigation signal down-conversion control word. The reflected down-conversion unit down-converts the intermediate frequency digital reflected signal according to the calculated reflected navigation signal Doppler frequency to obtain the reflected base frequency signal.

14. The space-borne multi -mode GNSS all -code interferometric signal processing system according to claim 11, wherein, The delay control unit determines a direct base frequency signal delay amount according to delay information of the local code DDM data and the initial interferometric data, and delays the direct base frequency signal according to the direct base frequency signal delay amount to obtain a second delayed direct base frequency signal. The interferometric correlation signal processing unit performs interferometric correlation and integral accumulation on the second delayed direct base frequency signal and the reflected base frequency signal to obtain adjusted interferometric data.

15. The space-borne multi-mode GNSS all-code interferometric signal processing system according to any one of claims 11-14, characterized in that, The baseband signal processing unit is disposed in a field programmable gate array chip.

16. The space-borne multi-mode GNSS all-code interferometric signal processing system according to any one of claims 11-14, characterized in that, The space-borne multi-mode GNSS full-code interferometric signal processing system is disposed on a low earth orbit satellite.

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