Method for capturing high-dynamic low-orbit satellite navigation enhanced signal

Abstract

The invention provides a method for capturing a high-dynamic low-orbit satellite navigation enhanced signal, and relates to the field of satellite navigation and low-orbit satellite service application. According to the method, low-earth-orbit satellite navigation enhanced signal features and application modes are fully utilized, dynamic estimation of low-earth-orbit satellite navigation enhanced signals is realized in a high and medium-earth-orbit satellite spatio-temporal information assisting mode, and the capturing dynamic range of a receiver is directly corrected through dynamic estimation of the signals. The capturing and searching range of the low-orbit satellite navigation enhanced signal is greatly reduced, the capturing time is shortened, and the capturing probability is improved; meanwhile, high-sensitivity capture of signals is realized by matching with a capture method of frequency domain zero-fill segmentation matched filtering, and an engineering solution is provided for overcoming the disadvantages of short enhancement visual arc section of low-orbit satellite navigation, large overhead scale of capture resources, limited application scene and the like.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation and low-orbit satellite service applications, and in particular 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 key infrastructure in the information age, providing accurate positioning, navigation and timing services to users around the world. With the advancement of technology and the increase in user demand, high-precision and robust navigation services are becoming increasingly important. Although technologies such as Precise Point Positioning (PPP), Real-time Kinematic ...

[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-orbit satellite navigation enhancement uses its proximity to the Earth and strong transmission power to improve positioning accuracy and anti-interference capabilities, thereby enhancing the performance of satellite navigation. However, the high dynamic characteristics of these signals and the increase in radial Doppler effect bring challenges to signal capture and processing, limiting the effectiveness of traditional capture methods.

[0005] Because traditional methods are limited in frequency domain search range and acquisition time, the high dynamic characteristics of low-orbit satellite navigation enhancement signals require new acquisition methods. At the same time, although extended two-dimensional correlation search is a solution to this limitation, 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 enhancement signals is the cornerstone for realizing advanced navigation applications and is crucial for integrating satellite navigation systems in different orbits. This technological breakthrough will improve navigation accuracy and anti-interference capabilities, and will have a far-reaching impact on the development of my country's comprehensive 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, a capture method based on high-dynamic low-orbit satellite navigation enhancement signals is proposed based on the existing high and medium-orbit satellite navigation constellations and traditional navigation signal capture and processing methods.

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

[0009] A method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals, characterized in that it comprises 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 of 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 visible 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 is a visible low-orbit satellite in the receiver's field of view according to the satellite almanac of the receiver in the constellation working mode corresponding to all high- and medium-orbit satellites. If there is no low-orbit satellite, do not start the low-orbit satellite navigation enhancement signal acquisition; if there is a low-orbit satellite, enter the low-orbit satellite navigation enhancement signal acquisition mode;

[0014] S5. In the low-orbit satellite navigation enhancement signal acquisition mode, firstly, the low-orbit satellite position information in the satellite almanac is screened; then, based on the low-orbit satellite position information and the receiver position, the Doppler dynamic estimation is performed on the low-orbit satellite navigation enhancement signal to obtain the 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 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;

[0015] S6. Use the frequency domain zero-filling segmented matched filtering capture method to perform 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] Further, 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, and 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] Further, 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 the 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 turns to the baseband signal processing link. Since the high and medium orbit satellites have a slow running speed and a small orbital Doppler, the satellite numbers of the high and medium orbit satellites are first searched, captured and tracked to complete the reception and processing of the high and medium orbit satellite navigation signals. Based on the processing results of the high and medium orbit satellite signals, the receiver's telegram demodulation and positioning solution processing are performed, and the receiver's time, position and satellite almanac data are obtained through navigation telegrams and positioning solutions. Then, the satellite almanac data is 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, firstly, the Doppler dynamic estimation of the low-orbit satellite navigation enhancement signal is performed based on the low-orbit satellite position and the receiver position in the satellite almanac data to obtain the Doppler estimation correction signal; then, according to 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 can be improved at the same time. After completing the signal Doppler correction, the signal capture processing 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 the signal dynamics, based on the traditional navigation signal capture method, the present invention adopts the frequency domain zero-filling segmented matching filtering method to capture the signal, obtain the carrier Doppler and pseudo code phase of the signal, and finally complete the low-orbit satellite navigation enhancement signal capture processing.

[0024] The method of the present invention makes full use of the signal characteristics and application modes of low-orbit satellite navigation enhancement, adopts the spatiotemporal information of high and medium-orbit satellites to realize dynamic estimation of low-orbit satellite navigation enhancement signals, directly corrects the capture dynamic range of the receiver through the dynamic estimation of the signal, greatly reduces the capture search range of the low-orbit satellite navigation enhancement signal, shortens the capture time, and improves the capture probability; at the same time, the capture method of frequency domain zero-filling segmented matched filtering is used to realize high-sensitivity capture of the signal, and provides an engineering solution to make up for the disadvantages of low-orbit satellite navigation enhancement, such as short visible arc segment, large capture resource overhead, and limited application scenarios.

[0025] Compared with the conventional navigation signal acquisition method in the background art for capturing 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 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 high-dynamic low-orbit satellite navigation enhancement signal capture units, 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. Based on the traditional satellite navigation time domain capture and frequency domain capture, the present invention innovatively proposes a capture method of frequency domain zero-filling segmented matched filtering. Without increasing logic resources, the parallel computing efficiency of signal capture is improved, the frequency domain loss caused by signal dynamics is reduced, the resource usage is small, the computational efficiency is high, and an efficient solution is provided for the capture of high-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 means of high- and medium-orbit spatiotemporal information assistance and frequency-domain zero-filling segmented matching filtering fusion, 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, such as low-orbit satellite navigation enhancement, low-orbit precise single-point positioning and low-orbit satellite communications. It has a wide range of applications and has good engineering realization and industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention 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 signal. DETAILED DESCRIPTION

[0033] In order to more clearly illustrate the technical solution and beneficial effects of the present invention, the present invention is further described below in conjunction with 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 logic 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 embodiment, it is assumed that there are 12 high- and medium-orbit navigation satellites and 2 low-orbit navigation enhancement satellites in the field of view, wherein the signal of the low-orbit navigation enhancement satellite is 1575.42MHz and the code rate is 10.23Mcps. This is used as an example to describe the high-dynamic low-orbit satellite navigation enhancement signal acquisition method in detail.

[0036] A method for capturing and processing a high-dynamic low-orbit satellite navigation enhancement signal 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, and 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 processing 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 sequentially capture and track them to complete the capture and tracking of the navigation signals of 12 visible high and medium orbit satellites in space.

[0039] S3. According to the navigation signals of visible high and medium orbit satellites, the visible high and medium orbit satellites are demodulated and positioned 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 visible low-orbit satellites within the receiver's field of view based on the receiver's satellite almanac in the constellation working mode corresponding to all high- and medium-orbit satellites; the almanac identifies that there are two low-orbit navigation enhancement satellites, so enter the low-orbit satellite navigation enhancement signal acquisition mode.

[0041] S5. In the low-orbit satellite navigation enhancement signal acquisition mode, firstly, the low-orbit satellite position information in the satellite almanac is screened; then Figure 2 As shown, 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, and 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] According to the frequency change value of the above-mentioned low-orbit satellite navigation enhancement signal, the Doppler adjustment amount of the carrier NCO in the digital frequency conversion processing is corrected respectively, and the dynamic correction amount of the pseudo code of the low-orbit satellite navigation enhancement signal is calculated to be 227Hz and 266Hz respectively, and the dynamic adjustment amount of the pseudo code NCO is corrected synchronously. The dynamic capture range of the low-orbit satellite navigation enhancement signal after the estimation correction is reduced from ±50KHz to ±5KHz, which greatly reduces the dynamic range of the capture search, shortens the capture time, and improves the capture probability. Finally, based on the dynamic parameters of the carrier and the pseudo code NCO, the low-orbit 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-filling 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 the frequency domain to obtain the frequency domain peak.

[0046] Specifically, 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; then the 128 matching results are padded with 128 zeros to make up 256 data bits; finally, the 256 data bits are searched for frequency domain peaks, and a two-dimensional correlation search between the code domain and the frequency domain is completed to obtain the frequency domain peaks. The frequency domain zero-padded segmented matched filtering process not only improves the sensitivity and capture frequency resolution of the signal, but also reduces the capture logic resource overhead of 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 high and medium orbit constellations in time and space, 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 matching filtering, which improves the high sensitivity and high resolution of high-dynamic signal capture. The fast, high-sensitivity, and high-resolution capture of low-orbit satellite navigation enhancement signals is achieved by organically integrating high and medium orbit constellations in time and space with frequency domain zero-filled segmented matching filtering, while reducing the scale of logical resources and the amount of computation for capture processing, occupying less resources, and having 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 of the invention is applicable to all low-orbit satellite high-dynamic signals such as low-orbit satellite navigation enhancement signals, low-orbit precision single-point positioning signals and low-orbit communication signals. It has a wide range of applications, a high level of engineering, and good engineering realization and industrial promotion value. It is of great significance to the development of low-orbit satellite navigation enhancement receivers and the construction of my country's high, medium and low-orbit collaborative navigation constellations.

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 of all visible high- and medium-orbit satellites in space; S3. According to the navigation signal of the visible high- and medium-orbit satellite, the visible 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 is a visible low-orbit satellite in the receiver's field of view according to the satellite almanac of the receiver in the constellation working mode corresponding to all high- and medium-orbit satellites. If there is no low-orbit satellite, do not start the capture 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 low-orbit satellite navigation enhancement signal acquisition mode, firstly, the low-orbit satellite position information in the satellite almanac is screened; then, based on the low-orbit satellite position information and the receiver position, the Doppler dynamic estimation of the low-orbit satellite navigation enhancement signal is performed to obtain the Doppler estimation correction signal; Then extract the baseband unit in the Doppler estimation correction signal to obtain the dynamic parameters of the carrier and pseudo code NCO of the baseband unit, so as to reduce 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-filling segmented matched filtering capture method to perform 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, characterized in that: In step S6, the frequency domain zero-filling 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; the 256 data bits are searched for frequency domain peaks, and a two-dimensional correlation search between the code domain and the frequency domain is completed to obtain the frequency domain peaks.

3. The method for capturing and processing high-dynamic low-orbit satellite navigation enhancement signals as claimed in claim 2, characterized in that: 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, and 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 as claimed in claim 3, characterized in that: 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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