Low-orbit satellite positioning time service signal receiving and processing method based on double sliding windows
Through the low-orbit satellite positioning timing signal reception processing method based on dual sliding windows, using data cache and partial matching filtering technology, the problem of receiving and processing of low-orbit satellite positioning timing signals in complex environments is solved, and the rapid detection and accuracy of signals are achieved. Synchronization improves reception success rate and efficiency, and is suitable for low-orbit satellite navigation enhancement and emergency positioning services.
Patent Information
- Application Number
- CN202411437237.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-15
- Publication Date
- 2025-01-10
AI Technical Summary
The prior art is difficult to effectively process low-orbit satellite positioning timing signals, especially in complex environments. Traditional communication signal processing and navigation signal processing methods cannot achieve accurate signal capture, tracking and measurement, resulting in high signal reception complexity and low efficiency. It cannot meet the measurement requirements of low-orbit satellite positioning timing signals.
Using low-orbit satellite positioning timing signal reception and processing method based on dual-sliding windows, the data cache, dual-sliding FFT window and partial matching filtering can be used to achieve rapid detection, precise synchronization and observation and acquisition of signals, reducing the correlation of signal processing The scale and computing volume improve the real-time and success rate of reception.
It successfully solved the difficulties in receiving and processing of low-orbit satellite positioning timing signals, improved the real-time and success rate of signal reception, reduced the demand for computing resources, realized the engineering realization of low-orbit satellite fusion positioning services, and provided Anti-interference and anti-deception capabilities in complex environments.
Smart Images
Figure CN119291735A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the application field of low-orbit satellite navigation enhancement and communication-navigation fusion positioning, and proposes a low-orbit satellite positioning and timing signal receiving and processing method based on a double sliding window. Background Art
[0002] As an important space-time infrastructure in the information age, the Global Navigation Satellite System (GNSS) plays an important supporting role in the military, industry, science, finance, consumption and other fields. With the continuous improvement of users' demand for service availability and the expansion of applications in complex environments, the "vulnerability" of GNSS is gradually exposed. First, GNSS satellites are medium- and high-orbit satellites. When the satellite navigation signal reaches the ground after space loss, it is already very weak, which is not enough to provide reliable and continuous positioning services in indoor, urban canyon, and forest cover. Second, the frequency and structure of GNSS signals are public and susceptible to deception and interference, so there are certain safety risks in complex electromagnetic environments. Therefore, the availability of GNSS in complex environments is seriously reduced, and its robustness, reliability and anti-interference performance need to be improved urgently.
[0003] Low-orbit satellite constellations have higher signal landing power, lower signal spatial loss and better Doppler characteristics, which can just make up for the "vulnerability" of GNSS. Therefore, navigation enhancement and communication and navigation fusion positioning applications based on low-orbit satellites have gradually become a hot research topic in the field of satellite navigation. With the vigorous development of large-scale low-orbit constellations such as Iridium, Starlink, OneWeb, and Telesat, navigation enhancement and communication and navigation fusion positioning application technology based on low-orbit satellites has become the most promising solution for future navigation enhancement and emergency positioning. At present, the positioning and timing (STL) service provided by Iridium is an important breakthrough in low-orbit satellite positioning and timing services. This service realizes the ability to serve as a backup or supplement to GNSS in complex environments through an independent low-orbit satellite positioning and timing signal that integrates communication and navigation. It effectively improves the performance of users' navigation and positioning services under signal shielding or even GNSS denial conditions.
[0004] The low-orbit satellite positioning and timing signal adopts a communication and navigation integrated signal system that is integrated with the low-orbit communication and navigation. This signal uses part of the downlink signaling beam on the basis of the communication signal to broadcast the navigation enhancement signal, realizing the integrated design of communication and navigation. The low-orbit satellite positioning and timing service signal is a specially designed positioning and timing signal. Compared with the traditional GNSS signal, the signal is a short burst signal instead of a continuous signal. The signal is a segmented signal instead of a fixed signal. The signal consists of three parts, namely the leading continuous wave, the pilot ranging code and the telegram data frame. The low-orbit satellite positioning and timing signal directly realizes the navigation and timing service without changing the original communication signal structure. However, while the low-orbit satellite positioning and timing signal completes navigation on the basis of realizing the integration of communication and navigation, it is at the cost of increasing the complexity of navigation signal reception. When receiving the low-orbit satellite positioning and timing signal, the receiver cannot complete the capture, tracking and measurement in the conventional satellite navigation signal processing method, but needs to focus on the real-time detection and reception of the burst signal. Therefore, there are certain limitations in processing the low-orbit satellite positioning and timing signal using the traditional communication signal processing and the traditional navigation signal processing methods.
[0005] 1. The low-orbit satellite positioning and timing signal is a signal system designed based on the low-orbit satellite communication signal structure. When the traditional communication signal processing method is used to process the low-orbit satellite positioning and timing signal, it can only complete the synchronization of the signal and the demodulation of the telegram data, and cannot obtain observation quantities such as signal Doppler and pseudo-range observation quantities. This method can only complete information acquisition but not observation quantity acquisition, and cannot meet the measurement requirements of low-orbit satellite positioning and timing signals, and has shortcomings in signal reception and processing;
[0006] 2. Traditional satellite navigation signal processing methods mainly process continuous signals in space, and complete capture and tracking through continuous signal iteration to obtain observation quantities and navigation message data. When using traditional satellite navigation signal processing methods to process low-orbit satellite positioning and timing signals, it is impossible to identify burst signals. At the same time, when processing segmented navigation signals, it is impossible to use traditional capture and tracking methods to achieve signal synchronization and navigation message acquisition. If low-orbit satellite positioning and timing signal processing is performed entirely in accordance with continuous wave processing, the demand for hardware logic resources will be huge, the computing efficiency will be low, and the engineering implementation will be weak.
[0007] How to realize the reception and processing of low-orbit satellite positioning and timing signals is the key to realizing the enhanced application of low-orbit satellite navigation. Solving the difficulties in the engineering implementation of the reception and processing algorithm of low-orbit satellite positioning and timing signals will realize the industrial promotion of low-orbit satellite communication and navigation fusion integrated applications. Research on the engineering implementation of the reception and processing of low-orbit satellite positioning and timing signals provides GNSS with an emergency backup solution with strong anti-interference, anti-spoofing and indoor positioning capabilities in complex environments. It is of great significance to the construction of my country's next-generation low-orbit communication and navigation fusion constellation, the development of low-orbit satellite navigation enhancement receivers, and the industrial promotion of low-orbit emergency safety positioning services. Summary of the invention
[0008] The method of the present invention is suitable for the engineering implementation of the reception processing of the receiver when receiving the low-orbit satellite communication and navigation fusion positioning and timing signals. It is mainly aimed at the problems and difficulties such as rapid detection, precise synchronization, telegram demodulation, and observation quantity acquisition in the processing of burst signals of low-orbit satellite communication and navigation fusion positioning and timing, and proposes a method for receiving and processing low-orbit satellite positioning and timing signals based on double sliding windows. This method innovatively proposes methods of signal processing fusion application such as data caching, double sliding windows and partial matching filtering to solve the burst and segmented signal modulation characteristics of low-orbit satellite positioning and timing signals, and provides an engineering feasible solution for the implementation of low-orbit satellite receivers and low-orbit satellite communication and navigation fusion positioning service applications.
[0009] The technical solution adopted by the present invention is:
[0010] A method for receiving and processing low-orbit satellite positioning and timing signals based on a double sliding window comprises the following steps:
[0011] (1) Receive the positioning and timing signals from low-orbit satellites, convert them into baseband signals through the RF front end, and then sample the baseband signals to obtain digital positioning and timing baseband signals, which include preamble signals, pilot signals, and data signals;
[0012] (2) Based on the continuous wave modulation characteristics of the pilot signal, the digital positioning and timing baseband signal is orthogonally modulated to obtain the signal energy, and then the signal energy is sequentially sent to two FFT windows for signal frequency domain peak detection. By sliding the energy peak between the two windows, the energy peak ratio of the two FFT windows is obtained, and the signal energy detection curve is obtained using the energy peak ratio;
[0013] (3) Compare the maximum value of the curve with the threshold. If the maximum value of the curve exceeds the threshold, the detection and identification of the leading signal is completed, and the detection flag, Doppler and starting time of the leading signal are output; if the maximum value does not exceed the threshold, return to step (2);
[0014] (4) Based on the Doppler and starting time obtained in the pilot signal detection and identification, the digital positioning timing baseband signal is initially dynamically corrected. Then, a correlator is formed using a partially matched filter to perform correlation operations between the local pseudo code and the pilot pseudo code. The filter output is then used as the input of the FFT to identify the frequency domain correlation peak, and the maximum value of the FFT result after modulus is used for threshold judgment.
[0015] (5) If the maximum value of the FFT exceeds the threshold, the synchronization measurement of the pilot signal is completed, and the synchronization mark, Doppler and synchronization pulse corresponding to the pilot signal are output; if it does not exceed the threshold, return to step (4);
[0016] (6) Use the Doppler and synchronization pulses obtained in the pilot signal synchronization measurement to accurately and dynamically correct the digital positioning and timing baseband signal, and then perform data signal correlation despreading, integral cleaning and phase detection filtering, as well as open-loop tracking of the code loop and carrier loop to achieve bit synchronization and frame synchronization of the message navigation frame and complete the demodulation of the message data frame; at the same time, output the phase detection error of the code loop and carrier loop as the carrier observation and pseudo-range observation of the data signal;
[0017] (7) The Doppler of the pilot signal, the Doppler of the pilot signal and the carrier observation of the data signal are fused to obtain the Doppler observation of the positioning and timing signal; the starting time of the pilot signal, the synchronization pulse of the pilot signal and the pseudorange observation of the data signal are fused to obtain the pseudorange observation of the positioning and timing signal; the Doppler observation, pseudorange observation and telegram data frame of the positioning and timing signal are output, and finally the reception and processing of the low-orbit satellite positioning and timing signal is completed.
[0018] Compared with the traditional communication signal processing and the traditional navigation signal processing method in the background technology, the present invention has the following advantages:
[0019] 1. Aiming at the segmented modulation characteristics of low-orbit satellite positioning and timing signals, the present invention innovatively adopts data caching to hierarchically realize the sequential and coordinated completion of signal detection, synchronization and demodulation. The signal reception has strong real-time performance and high success rate, and can solve the difficulties in the segmented reception and processing of low-orbit satellite signals.
[0020] 2. Aiming at the burst modulation characteristics of low-orbit satellite positioning and timing signals, the present invention innovatively introduces a burst signal detection algorithm with dual sliding FFT windows, and realizes accurate detection and identification of burst signals by sequentially passing the energy flow of the signal through two sliding FFT windows. Compared with the traditional frequency domain energy detection method, it has the advantages of high detection success rate and low false alarm rate for high-dynamic low-orbit signals.
[0021] 3. The present invention optimizes the design of the traditional satellite navigation signal processing algorithm and constructs a pilot ranging signal synchronization algorithm based on partial matching filtering and frequency domain search. The partial matching filtering and frequency domain search of multi-branch signals reduce the scale of the correlator and the amount of calculation for signal processing, occupy less resources, have high calculation efficiency, and have the advantages of accurate signal synchronization.
[0022] 4. Based on the modulation characteristics of low-orbit satellite positioning and timing signals, the present invention solves the engineering problem of receiving and processing sudden high-dynamic low-orbit satellite signals by integrating multiple means, and provides a solution for receiving and processing low-orbit satellite positioning and timing signals and emergency backup navigation and positioning services for low-orbit satellites. It has a wide range of applications, a high level of achievability, and good engineering realization and industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 The present invention is a flow chart of a method for receiving and processing low-orbit satellite positioning and timing signals based on double sliding windows. DETAILED DESCRIPTION
[0024] Reference Figure 1 The present invention mainly aims at the burst and segmented modulation characteristics of low-orbit satellite positioning and timing signals, and the difficulty of being unable to be processed according to the traditional satellite navigation signal processing mode during the reception and processing. A low-orbit satellite positioning and timing signal reception and processing method based on a double sliding window is proposed.
[0025] The method first completes the reception, frequency conversion, sampling and buffering of spatial signals, and then performs digital baseband signal processing. The burst modulation characteristics of the leading continuous wave signal of the low-orbit satellite positioning and timing signal are used to complete the signal detection and identification through the double sliding window FFT method to obtain the signal Doppler and signal starting time; the detected signal enters the synchronization and measurement stage, and on the basis of the traditional satellite navigation signal processing algorithm, the signal synchronization measurement algorithm of partial matched filtering and frequency domain search for the pilot ranging signal is designed by improving the algorithm to complete the acquisition of the pilot Doppler of the pilot ranging signal and the acquisition of the pilot synchronization pulse; after completing the signal synchronization and measurement, the closed-loop tracking and demodulation of the telegram data frame is started, and the telegram navigation frame is closed-loop tracked and data demodulated according to the traditional satellite navigation signal tracking mode to obtain the carrier loop and code loop phase error and telegram data; finally, the signal Doppler, pilot Doppler, carrier tracking error and other data generated in the above steps are fused to obtain the Doppler observation, and the signal starting time, pilot synchronization pulse and code loop phase error and other data are fused to obtain the pseudorange observation. After the Doppler observations, pseudorange observations, and telegram data frames are output, the reception and processing of the low-orbit satellite positioning and timing signals are finally completed.
[0026] like Figure 1As shown, a flow chart of a method for receiving and processing low-orbit satellite positioning and timing signals based on a dual sliding window is shown. In a specific embodiment, the low-orbit satellite positioning and timing signal is set to a 1.6GHz L narrowband signal, wherein the low-orbit satellite positioning and timing signal is broadcast using a standard downlink signaling beam. The information rate is 50Kbps, wherein the single carrier length of the preamble signal is 100 bits, the ranging code length of the pilot signal is 100 bits, and the data signal telegram frame length is 500 bits. This is used as an example for analyzing the receiving and processing method. The steps of the method for receiving and processing low-orbit satellite positioning and timing signals based on a dual sliding window are as follows:
[0027] Step 1: Receive the positioning and timing signal from the low-orbit satellite in space, convert the L-band RF signal into an intermediate frequency signal through the RF front end, sample the intermediate frequency signal, and then perform orthogonal digital frequency conversion processing to obtain a digital positioning and timing baseband signal. The digital positioning and timing baseband signal includes a preamble signal, a pilot signal, and a data signal.
[0028] Step 2: Perform real-time detection and identification on the digital positioning and timing baseband signal. Utilize the continuous wave modulation characteristics of the pilot signal to extract and low-pass filter the digital positioning and timing baseband signal. According to the signal Doppler dynamic range of ±50KHz, perform low-pass extraction and filtering on the digital positioning and timing baseband signal to obtain a 256KHz baseband orthogonal signal. Perform modulus calculation on the baseband orthogonal signal to obtain the signal energy. At the same time, construct two 1024-point FFT windows, sequentially send the obtained signal energy to the two FFT windows, divide the converted peak values of the two FFT windows to obtain the signal peak ratio, and use the energy peak ratio to obtain the signal energy detection curve.
[0029] Step 3, compare the maximum value of the curve with the threshold to complete the signal peak detection; if the maximum value of the curve exceeds the peak value of the threshold, the detection and identification of the positioning timing leading signal is realized, and the detection flag, Doppler and starting time of the leading signal are output; if the maximum value does not exceed the threshold, return to step (2);
[0030] Step 4: After the positioning and timing pilot signal is detected and identified, start the synchronous measurement of the pilot signal. Use the signal Doppler and starting time obtained in the pilot signal detection and identification to perform initial dynamic corrections on the local carrier and pseudo code NCO of the digital positioning and timing baseband signal, set the related matching filters of the three branches of advance, alignment, and lag, the length of the matching filter is 10, the number of points of the frequency domain FFT is 128 points, and use some matching filters to form a multi-branch correlator to complete the correlation operation between the local pseudo code and the pilot signal pseudo code. Then use the output of the matching filter as the input of the FFT to perform FFT peak judgment, and use the maximum value of the FFT result after modulo to perform threshold judgment to complete the synchronization and measurement of the pilot signal;
[0031] Step 5: If the maximum value of FFT exceeds the threshold, the synchronization measurement of the pilot signal is completed, and the synchronization mark, Doppler and synchronization pulse corresponding to the pilot signal are output; if it does not exceed the threshold, return to step (4);
[0032] Step 6. After the positioning and timing pilot signal completes the synchronous measurement, start the data signal tracking and demodulation. Use the pilot Doppler and synchronization pulses obtained in the pilot signal synchronous measurement to accurately and dynamically correct the local carrier and pseudo-code NCO of the digital positioning and timing baseband signal, and start the tracking and demodulation of the data signal. First, perform data signal correlation demodulation, and then perform integral cleaning and phase-detection filtering to achieve open-loop tracking of the code loop and the carrier loop. Realize the bit synchronization and frame synchronization of the telegram navigation frame, and complete the demodulation of the telegram data frame. At the same time, output the phase-detection error of the code loop and the carrier loop as the carrier observation and pseudo-range observation of the data signal;
[0033] Step 7: After completing the data signal tracking and demodulation, the Doppler of the pilot signal, the Doppler of the pilot signal and the carrier observation of the data signal are fused to obtain the Doppler observation of the positioning and timing signal. The starting time of the pilot signal, the synchronization pulse of the pilot signal and the pseudo-range observation of the data signal are fused to obtain the pseudo-range observation of the positioning and timing signal. After the Doppler observation, pseudo-range observation and telegram data frame of the positioning and timing signal are output, the reception and processing of the low-orbit satellite positioning and timing signal is finally completed.
[0034] The working principle of the present invention is as follows:
[0035] The present invention proposes a method for receiving and processing low-orbit satellite positioning and timing signals based on a double sliding window. This method is aimed at the engineering realization requirements of receiving and processing low-orbit satellite positioning and timing signals, fully analyzes the segmentation and burst modulation characteristics of the signal, and uses the data cache method to realize the sequential processing of the segmented signal; uses the double sliding FFT window to realize the real-time detection and identification of the burst signal; uses partial matching filtering and frequency domain search to realize the precise synchronization and measurement of the pilot ranging signal; uses closed-loop tracking and dynamic assistance to realize the rapid demodulation of the telegram data frame; after obtaining Doppler observations, pseudo-range observations, telegram data frames and other data, the reception and processing of the low-orbit satellite positioning and timing signals is finally completed. This method innovatively integrates algorithms such as data hierarchical caching, double sliding windows, partial matching filtering and closed-loop tracking of burst signals, solves the difficulties of burst and real-time reception and processing of low-orbit satellite positioning and timing signals, and reduces the scale and amount of calculation of the correlator of signal processing, occupies less resources and has high calculation efficiency. It provides an engineering solution for the reception and processing of low-orbit satellite positioning and timing signals and the navigation and positioning enhancement service of low-orbit satellites.
[0036] This method has a wide range of applications, a high level of achievability, and good engineering implementation and industrial promotion value. It is of great significance to the construction of my country's next-generation low-orbit communication and navigation fusion constellation, the development of low-orbit satellite navigation enhancement receivers, and the industrialization and promotion of low-orbit emergency positioning service applications.
Claims
1. A method for receiving and processing low-orbit satellite positioning and timing signals based on a double sliding window, characterized in that: The steps include: (1) Receive the positioning and timing signals from low-orbit satellites, convert them into baseband signals through the RF front end, and then sample the baseband signals to obtain digital positioning and timing baseband signals, which include preamble signals, pilot signals, and data signals; (2) Based on the continuous wave modulation characteristics of the pilot signal, the digital positioning and timing baseband signal is orthogonally modulated to obtain the signal energy, and then the signal energy is sequentially sent to two FFT windows for signal frequency domain peak detection. By sliding the energy peak between the two windows, the energy peak ratio of the two FFT windows is obtained, and the signal energy detection curve is obtained using the energy peak ratio; (3) Compare the maximum value of the curve with the threshold. If the maximum value of the curve exceeds the threshold, the detection and identification of the leading signal is completed, and the detection flag, Doppler and starting time of the leading signal are output; If the maximum value does not exceed the threshold, return to step (2); (4) Based on the Doppler and starting time obtained in the pilot signal detection and identification, the digital positioning timing baseband signal is initially dynamically corrected. Then, a correlator is formed using a partially matched filter to perform correlation operations between the local pseudo code and the pilot pseudo code. The filter output is then used as the input of the FFT to identify the frequency domain correlation peak, and the maximum value of the FFT result after modulus is used for threshold judgment. (5) If the maximum value of the FFT exceeds the threshold, the synchronization measurement of the pilot signal is completed, and the synchronization mark, Doppler and synchronization pulse corresponding to the pilot signal are output; If the threshold value is not exceeded, return to step (4); (6) Use the Doppler and synchronization pulses obtained in the pilot signal synchronization measurement to accurately and dynamically correct the digital positioning and timing baseband signal, and then perform data signal correlation despreading, integral cleaning and phase detection filtering, as well as open-loop tracking of the code loop and carrier loop to achieve bit synchronization and frame synchronization of the message navigation frame and complete the demodulation of the message data frame; at the same time, output the phase detection error of the code loop and carrier loop as the carrier observation and pseudo-range observation of the data signal; (7) The Doppler of the pilot signal, the Doppler of the pilot signal and the carrier observation of the data signal are fused to obtain the Doppler observation of the positioning and timing signal; the starting time of the pilot signal, the synchronization pulse of the pilot signal and the pseudorange observation of the data signal are fused to obtain the pseudorange observation of the positioning and timing signal; the Doppler observation, pseudorange observation and telegram data frame of the positioning and timing signal are output, and finally the reception and processing of the low-orbit satellite positioning and timing signal is completed.