A method for acquiring a high dynamic low earth orbit satellite navigation augmentation signal

Abstract

The application provides a high-dynamic low-orbit satellite navigation enhanced signal acquisition method, and relates to the fields of satellite navigation and low-orbit satellite service application.The method fully utilizes the signal characteristics and application mode of the low-orbit satellite navigation enhancement, realizes dynamic estimation of the low-orbit satellite navigation enhancement signal in a high-middle-orbit satellite space-time information auxiliary mode, directly corrects the acquisition dynamic range of the receiver through the dynamic estimation of the signal, greatly reduces the acquisition search range of the low-orbit satellite navigation enhancement signal, shortens the acquisition time, and improves the acquisition probability; meanwhile, the high-sensitivity acquisition of the signal is realized by cooperating with the acquisition method of the frequency domain zero-padding segmented matched filtering, and an engineering solution is provided for the disadvantages of the low-orbit satellite navigation enhancement, such as short visible arc segment, large acquisition resource cost, and limited application scene.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation and low-orbit satellite service applications, and more particularly to a method for capturing high-dynamic low-orbit satellite navigation enhancement signals. The method uses information from high- and medium-orbit satellites to quickly and accurately capture low-orbit satellite signals. Background Art

[0002] The Global Navigation Satellite System (GNSS) is a critical infrastructure in the information age, providing precise positioning, navigation, and timing services to users worldwide. With technological advancements and increasing user demand, high-precision and robust navigation services are becoming increasingly important. Despite significant advances in technologies such as Precise Point Positioning (PPP), Real-Time Kinematic (RTK), and various augmentation systems, such as the Ground-Based Augmentation System (GBAS) and the Satellite-Based Augmentation System (SBAS), they still have limitations and cannot fully meet the widespread demand for high-performance navigation services from global users.

[0003] Low Earth Orbit satellite constellations offer a cost-effective way to enhance global satellite navigation services, making them more accurate and reliable without relying on ground-based base stations. These constellations are expected to be a key technology to address the limitations of current navigation services.

[0004] Low-Earth Orbit (LEO) satellite navigation augmentation utilizes its proximity to Earth and high transmit power to improve positioning accuracy and anti-interference capabilities, thereby enhancing satellite navigation performance. However, the high dynamic characteristics of these signals and the increased radial Doppler effect pose challenges to signal capture and processing, limiting the effectiveness of traditional capture methods.

[0005] The high dynamics of LEO satellite navigation enhancement signals require new acquisition methods, as traditional methods are limited in frequency domain search range and acquisition time. While extended two-dimensional correlation search offers a solution to these limitations, its hardware resource consumption and low computational efficiency limit its feasibility in engineering practice.

[0006] The effective capture and processing of high-dynamic, low-orbit satellite navigation augmentation signals is the cornerstone for advanced navigation applications and crucial for integrating satellite navigation systems in different orbits. This technological breakthrough will enhance navigation accuracy and anti-interference capabilities, and will have a profound impact on the development of my country's integrated navigation service system. Summary of the Invention

[0007] The purpose of the present invention is to address the deficiencies in the above-mentioned background technology. By fully analyzing the signal characteristics and application modes of low-orbit satellite navigation enhancement signals, based on the existing high and medium-orbit satellite navigation constellations and traditional navigation signal capture and processing methods, a capture method based on high-dynamic low-orbit satellite navigation enhancement signals is proposed.

[0008] The technical solution adopted in the present invention is as follows:

[0009] A method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals, characterized by comprising the following steps:

[0010] S1. Using a receiver to receive a space satellite navigation signal, preprocessing the received space satellite navigation signal to obtain a digital baseband signal;

[0011] S2. Number the high- and medium-orbit satellites in the digital baseband signal, and then sequentially capture and track them to obtain navigation signals from all visible high- and medium-orbit satellites in space;

[0012] S3. According to the navigation signal of the visible high- and medium-orbit satellite, the visual high- and medium-orbit satellite is demodulated and positioned to obtain the time, position and satellite almanac of the receiver in the constellation working mode corresponding to all high- and medium-orbit satellites;

[0013] S4. Determine whether there are any visible LEO satellites within the receiver's field of view based on the receiver's satellite almanac in the constellation operating mode corresponding to all high and low-Earth orbit satellites. If no LEO satellites are present, do not initiate LEO satellite navigation enhancement signal acquisition. If a LEO satellite is present, enter LEO satellite navigation enhancement signal acquisition mode.

[0014] S5. In the LEO satellite navigation augmentation signal acquisition mode, first, the LEO satellite position information in the satellite almanac is screened; then, based on the LEO satellite position information and the receiver position, a Doppler dynamic estimation is performed on the LEO satellite navigation augmentation signal to obtain a Doppler estimation correction signal; then, the baseband unit in the Doppler estimation correction signal is extracted to obtain dynamic parameters of the baseband unit's carrier and pseudo-code NCO to narrow the dynamic range of the LEO satellite navigation augmentation signal acquisition, reduce the acquisition time, and improve the acquisition probability; finally, based on the dynamic parameters of the carrier and pseudo-code NCO, the LEO satellite navigation augmentation signal is captured from the digital baseband signal in step S1;

[0015] S6. Use the frequency domain zero-padding segmented matched filtering capture method to perform a two-dimensional correlation capture search in the code domain and frequency domain on the low-orbit satellite navigation enhancement signal obtained in step S5 to obtain the frequency domain peak; determine the carrier Doppler and pseudo-code phase of the captured low-orbit satellite navigation enhancement signal through the frequency domain peak, and finally complete the capture and processing of the high-dynamic low-orbit satellite navigation enhancement signal.

[0016] Furthermore, in step S1, the preprocessing step includes: converting the space satellite navigation signal into an intermediate frequency signal; sampling the intermediate frequency signal to obtain a sampled signal; and performing orthogonal digital frequency conversion processing on the sampled signal to obtain a digital baseband signal.

[0017] Furthermore, in step S5, the Doppler dynamic estimation is performed on the low-orbit satellite navigation enhancement signal according to the following formula:

[0018]

[0019] Among them, f d is the frequency change value of the signal, V s is the satellite speed, R e is the radius of the Earth, R s is the height of the satellite from the center of the earth, θ is the signal arrival angle, f c is the carrier frequency, c is the speed of light;

[0020] Based on the frequency change value f d The low-orbit satellite navigation enhancement signal is corrected to obtain the Doppler estimation correction signal.

[0021] Furthermore, in step S6, the frequency domain zero-padding segmented matched filtering capture method includes: dividing the pseudo-code period of the low-orbit satellite navigation enhancement signal into code segments with a length of 80 code chips, matching and filtering all code segments with the digital baseband signal to obtain 128 matching results; then performing 128 zero-padding processing on the 128 matching results to make up 256 data bits; finally, performing frequency domain peak search on the 256 data bits, completing a two-dimensional correlation search between the code domain and the frequency domain, and obtaining a frequency domain peak.

[0022] The working principle of the present invention is as follows:

[0023] The method of the present invention receives and processes space satellite navigation signals in accordance with a normal navigation signal processing method, completes signal reception, frequency conversion, sampling and caching; and then proceeds to the baseband signal processing link. Since the operating speed of high and medium orbit satellites is slow and their own orbital Doppler is small, the satellite numbers of high and medium orbit satellites are first searched, captured and tracked to complete the reception and processing of high and medium orbit satellite navigation signals. Based on the processing results of the high and medium orbit satellite signals, the receiver's message demodulation and positioning solution processing are performed, and the receiver's time, position and satellite almanac data are obtained through the navigation message and positioning solution. The satellite almanac data is then used to determine whether there is a visible low-orbit satellite in the field of view. If there is no visible low-orbit satellite, the low-orbit satellite navigation enhancement signal capture is not performed. If there is a visible low-orbit satellite, the low-orbit satellite navigation enhancement signal capture mode is turned on. After entering the low-orbit satellite navigation enhancement signal capture mode, the low-orbit satellite navigation enhancement signal is first dynamically estimated based on the low-orbit satellite position and receiver position in the satellite almanac data to obtain a Doppler estimation correction signal; then, based on the dynamic parameters of the carrier and pseudo-code NCO in the baseband unit of the Doppler estimation correction signal, the capture search range of the low-orbit satellite navigation enhancement signal is narrowed, the capture time is reduced, and the capture probability is increased. After completing the signal Doppler correction, the signal capture process is started; in order to improve the capture sensitivity and capture probability of the low-orbit satellite navigation enhancement signal and reduce the frequency domain loss caused by signal dynamics, based on the traditional navigation signal capture method, the present invention adopts the frequency domain zero-padding segmented matched filtering method to perform signal capture, obtain the signal's carrier Doppler and pseudo-code phase, and finally complete the low-orbit satellite navigation enhancement signal capture process.

[0024] The method of the present invention fully utilizes the signal characteristics and application modes of low-orbit satellite navigation enhancement, adopts the spatiotemporal information of high and medium-orbit satellites to assist in realizing dynamic estimation of low-orbit satellite navigation enhancement signals, and directly corrects the capture dynamic range of the receiver through the dynamic estimation of the signal, thereby greatly reducing the capture search range of the low-orbit satellite navigation enhancement signal, shortening the capture time, and improving the capture probability; at the same time, the method cooperates with the capture method of frequency domain zero-padding segmented matched filtering to realize high-sensitivity capture of the signal, providing an engineering solution to make up for the disadvantages of low-orbit satellite navigation enhancement, such as a short visible arc, large capture resource overhead, and limited application scenarios.

[0025] Compared with the conventional navigation signal acquisition method used in the background art to capture high-dynamic low-orbit satellite navigation enhancement signals, the present invention has the following advantages:

[0026] 1. Aiming at the enhanced application mode of low-orbit satellite navigation enhancement signals, the present invention innovatively proposes to use the spatiotemporal information of high and medium-orbit satellites to assist in the high-dynamic capture of low-orbit satellites, thereby achieving rapid and accurate capture of low-orbit satellite navigation enhancement signals and providing a time guarantee for the service availability of low-orbit satellite navigation enhancement.

[0027] 2. Based on the constellation time, position and satellite almanac of high and medium orbit satellites, the present invention reduces the capture range of high-dynamic low-orbit satellite navigation enhancement signals by more than ten times, reduces the complexity and logical resource scale of the high-dynamic low-orbit satellite navigation enhancement signal capture unit, improves the signal capture sensitivity, and provides engineering guarantees for the design of low-orbit satellite receivers and the application of low-orbit satellite navigation enhancement services.

[0028] 3. Building on traditional satellite navigation capture methods in the time and frequency domains, this invention innovatively proposes a frequency-domain zero-padding segmented matched filtering capture method. Without increasing logic resources, this method improves the efficiency of parallel signal capture and reduces frequency domain losses caused by signal dynamics. With minimal resource consumption and high computational efficiency, it provides a highly efficient solution for capturing highly dynamic low-orbit satellite navigation signals.

[0029] 4. The present invention solves the engineering application problem of high-dynamic capture of low-orbit satellite navigation enhancement signals by integrating high and medium orbit spatiotemporal information assistance with frequency domain zero-padding segmented matched filtering, providing a receiver engineering implementation approach for realizing low-orbit satellite navigation enhancement services and low-orbit fusion application services.

[0030] 5. The present invention is applicable to high-dynamic signals of all low-orbit satellites, including low-orbit satellite navigation enhancement, low-orbit precise single-point positioning and low-orbit satellite communications. It has a wide range of applications and good engineering realization and industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart for capturing a high-dynamic low-orbit satellite navigation enhancement signal;

[0032] Figure 2 Schematic diagram of Doppler calculation for low-orbit satellite navigation enhancement signals. DETAILED DESCRIPTION

[0033] In order to more clearly illustrate the technical solutions and beneficial effects of the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] The present invention aims to solve the capture problems of low-orbit satellite navigation enhancement signals, such as large dynamics, wide search frequency domain range, long capture time, and large scale of logical resources occupied by capture, by giving full play to the spatiotemporal information auxiliary advantages of high and medium-orbit satellites, integrating the improved method of traditional satellite navigation signal capture and processing, and proposing a capture method for high-dynamic low-orbit satellite navigation enhancement signals.

[0035] In this example, a total of 12 high- and medium-orbit navigation satellites and two low-orbit navigation augmentation satellites are assumed within the field of view. The signal of the low-orbit navigation augmentation satellites is 1575.42 MHz and has a bit rate of 10.23 Mcps. This is used as an example to describe the method for capturing high-dynamic low-orbit satellite navigation augmentation signals.

[0036] A method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals in this embodiment is as follows: Figure 1 As shown, the following steps are included:

[0037] S1. Receive a space satellite navigation signal using a receiver, convert the received space satellite navigation signal into an intermediate frequency signal; sample the intermediate frequency signal to obtain a sampled signal; and perform orthogonal digital frequency conversion on the sampled signal to obtain a digital baseband signal.

[0038] S2. Number the high and medium orbit satellites in the digital baseband signal according to the traditional satellite navigation reception and processing mode, and then perform sequential capture and tracking to complete the capture and tracking of the navigation signals of 12 visible high and medium orbit satellites in space.

[0039] S3. Based on the navigation signals of visible high and medium orbit satellites, perform telegram demodulation and positioning calculation on the visible high and medium orbit satellites to obtain the time, position and satellite almanac of the receiver in the constellation working mode corresponding to the 12 high and medium orbit satellites.

[0040] S4. Determine whether there are any visible low-orbit satellites within the receiver's field of view based on the receiver's satellite almanac in the constellation operating mode corresponding to all high- and medium-orbit satellites. The almanac identifies the presence of two low-orbit navigation augmentation satellites, and therefore enters the low-orbit satellite navigation augmentation signal acquisition mode.

[0041] S5. In the low-orbit satellite navigation enhancement signal acquisition mode, first filter the low-orbit satellite position information in the satellite almanac; then Figure 2 As shown in Figure 1, the Doppler dynamic estimation of the low-orbit satellite navigation enhancement signal is performed based on the low-orbit satellite position information and the receiver position:

[0042]

[0043] Among them, f d is the frequency change value of the signal, V s is the satellite speed, R e is the radius of the Earth, R s is the height of the satellite from the center of the earth, θ is the signal arrival angle, f c is the carrier frequency, c is the speed of light; in this embodiment, the orbital frequency changes of the two low-orbit satellites relative to the receiver are +35KHz and -41KHz respectively.

[0044] Based on the frequency change of the LEO satellite navigation enhancement signal, the Doppler adjustment of the carrier NCO in the digital frequency conversion process is corrected. The dynamic corrections of the pseudo-code of the LEO satellite navigation enhancement signal are calculated to be 227Hz and 266Hz, respectively, and the dynamic adjustment of the pseudo-code NCO is also corrected. After the estimated correction, the dynamic capture range of the LEO satellite navigation enhancement signal is reduced from ±50kHz to ±5kHz, significantly reducing the dynamic range of the capture search, shortening the capture time, and improving the capture probability. Finally, based on the dynamic parameters of the carrier and pseudo-code NCO, the LEO satellite navigation enhancement signal is captured from the digital baseband signal in step S1.

[0045] S6. In order to cope with the frequency domain loss caused by the dynamics of the low-orbit satellite navigation enhancement signal and improve the capture sensitivity, a frequency domain zero-padding segmented matched filtering capture method is designed based on the traditional navigation signal capture method. The low-orbit satellite navigation enhancement signal obtained in step S5 is subjected to a two-dimensional correlation capture search in the code domain and frequency domain to obtain the frequency domain peak.

[0046] Specifically, the pseudo-code period of the low-orbit satellite navigation augmentation signal is divided into segments of 80 chips in length. All segments are then matched with the digital baseband signal to obtain 128 matching results. These 128 matching results are then padded with 128 zeros to create 256 data bits. Finally, a frequency domain peak search is performed on these 256 data bits, completing a two-dimensional correlation search between the code and frequency domains to obtain the frequency domain peak. This frequency domain zero-padding segmented matched filtering process improves signal capture sensitivity and frequency resolution while reducing the logic resource overhead for capturing dynamic signals.

[0047] Finally, the carrier Doppler and pseudo code phase of the captured low-orbit satellite navigation enhancement signal are determined by frequency domain peak judgment, and the capture and processing of the high-dynamic low-orbit satellite navigation enhancement signal is finally completed.

[0048] The method of the present invention innovatively proposes a low-orbit dynamic estimation and correction method assisted by the spatiotemporal assistance of high and medium orbit constellations, which solves the difficulty of high-dynamic capture and processing of low-orbit satellite navigation enhancement signals. At the same time, it innovatively designs a two-dimensional search method of frequency-domain zero-filled segmented matched filtering, which improves the high sensitivity and high resolution of high-dynamic signal capture. By organically integrating the spatiotemporal assistance of high and medium orbit constellations with the frequency-domain zero-filled segmented matched filtering, fast, high-sensitivity, and high-resolution capture of low-orbit satellite navigation enhancement signals is achieved, while reducing the scale of logical resources and the amount of computation required for capture processing, occupying fewer resources, and achieving high computational efficiency. It provides an engineering solution for the reception and processing of low-orbit satellite navigation enhancement signals and low-orbit satellite navigation enhancement services.

[0049] The method proposed in this paper is applicable to all high-dynamic signals from low-orbit satellites, including low-orbit navigation augmentation signals, low-orbit precise point positioning signals, and low-orbit communication signals. It has a wide range of applications, a high level of engineering feasibility, and excellent engineering implementation and industrialization value. It is of great significance to the development of low-orbit satellite navigation augmentation receivers and the construction of coordinated navigation constellations for high, medium, and low-orbit satellites in my country.

Claims

1. A method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals, characterized in that: The steps include: S1. Using a receiver to receive a space satellite navigation signal, preprocessing the received space satellite navigation signal to obtain a digital baseband signal; S2. Number the high- and medium-orbit satellites in the digital baseband signal, and then sequentially capture and track them to obtain navigation signals from all visible high- and medium-orbit satellites in space; S3. According to the navigation signal of the visible high- and medium-orbit satellite, the visual high- and medium-orbit satellite is demodulated and positioned to obtain the time, position and satellite almanac of the receiver in the constellation working mode corresponding to all high- and medium-orbit satellites; S4. Determine whether there are any visible low-orbit satellites within the receiver's field of view based on the receiver's satellite almanac in the constellation operating mode corresponding to all high- and medium-orbit satellites. If no low-orbit satellites are present, do not initiate acquisition of the low-orbit satellite navigation enhancement signal. If there are low-orbit satellites, enter the low-orbit satellite navigation enhanced signal acquisition mode; S5. In the LEO navigation augmentation signal acquisition mode, first, the LEO satellite position information in the satellite almanac is filtered; then, based on the LEO satellite position information and the receiver position, a Doppler dynamic estimation is performed on the LEO navigation augmentation signal to obtain a Doppler estimation correction signal; Then, the baseband unit in the Doppler estimation correction signal is extracted to obtain the dynamic parameters of the carrier and pseudo-code NCO of the baseband unit, so as to narrow the capture dynamic range of the low-orbit satellite navigation enhancement signal, reduce the capture time, and improve the capture probability. Finally, based on the dynamic parameters of the carrier and pseudo-code NCO, the low-orbit satellite navigation enhancement signal is captured from the digital baseband signal in step S1. S6. Use the frequency domain zero-padding segmented matched filtering capture method to perform a two-dimensional correlation capture search in the code domain and frequency domain on the low-orbit satellite navigation enhancement signal obtained in step S5 to obtain the frequency domain peak; determine the carrier Doppler and pseudo-code phase of the captured low-orbit satellite navigation enhancement signal through the frequency domain peak, and finally complete the capture and processing of the high-dynamic low-orbit satellite navigation enhancement signal.

2. The method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals according to claim 1, wherein: In step S6, the frequency domain zero-padding segmented matched filtering capture method includes: The pseudo-code period of the low-orbit satellite navigation enhancement signal is divided into code segments with a length of 80 code chips, and all code segments are matched and filtered with the digital baseband signal to obtain 128 matching results; the 128 matching results are padded with 128 zeros to make up 256 data bits; a frequency domain peak search is performed on the 256 data bits, and a two-dimensional correlation search between the code domain and the frequency domain is completed to obtain the frequency domain peak.

3. The method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals according to claim 2, wherein: In step S5, the Doppler dynamic estimation is performed on the low-orbit satellite navigation enhancement signal according to the following formula: Among them, f d is the frequency change value of the signal, V s is the satellite speed, R e is the radius of the Earth, R s is the height of the satellite from the center of the earth, θ is the signal arrival angle, f c is the carrier frequency, c is the speed of light; Then based on the frequency change value f d The low-orbit satellite navigation enhancement signal is corrected to obtain the Doppler estimation correction signal.

4. The method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals according to claim 3, wherein: In step S1, the preprocessing step includes: converting the space satellite navigation signal into an intermediate frequency signal; sampling the intermediate frequency signal to obtain a sampled signal; and performing orthogonal digital frequency conversion processing on the sampled signal to obtain a digital baseband signal.

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