CN-121995407-A - Quick capturing method and system for low-rail high-dynamic signals

Abstract

A fast capturing method for low-orbit high-dynamic signal includes receiving intermediate frequency signal, carrying out correlation operation on local pseudo code and said intermediate frequency signal to search code phase, sliding said local binary phase shift keying modulation BPSK pseudo code by stepping amount corresponding to number of parallel correlators on code phase to complete coarse capturing of code phase after each correlation operation, applying multiple different Doppler frequency compensation values to said intermediate frequency signal in sequence according to coarse captured code phase of code phase, repeating correlation operation after each compensation, generating Doppler frequency compensation value corresponding to maximum correlation peak and determining as optimal Doppler frequency estimation value. The application solves the difficult problem of MCSK signal code phase discontinuity in the capturing process, and greatly improves the signal capturing speed.

Inventors

• HAN ZHENGWEN
• WANG CAIXIA
• MA JUNWEI
• TIAN YU
• ZHAI JIANYONG
• LI MENGYUAN
• HE YANWEI
• SU CUIPING
• GAO LI
• ZHANG LIANGRU

Assignees

• 中国电子科技集团公司第二十研究所

Dates

Publication Date

20260508

Application Date

20260122

Claims (8)

1. 1. A method for rapidly capturing a high dynamic signal of a low track, comprising: Receiving an intermediate frequency signal, searching a code phase by carrying out correlation operation on a local pseudo code and the intermediate frequency signal, and enabling the local binary phase shift keying modulation (BPSK) pseudo code to slide on the code phase by a stepping amount corresponding to the number of parallel correlators after each correlation operation; And the frequency secondary searching step is to sequentially apply a plurality of different Doppler frequency compensation values to the intermediate frequency signal according to the coarse captured code phase of the code phase, repeatedly perform correlation operation after each compensation, compare correlation peaks obtained under each compensation, and determine the Doppler frequency compensation value corresponding to the maximum correlation peak to be the optimal Doppler frequency estimation value.
2. 2. The method of claim 1, wherein the step of correlating the local pseudocode with the intermediate frequency signal to search for the code phase is performed by using a multipath parallel correlator to simultaneously calculate correlation values for a plurality of adjacent code phases.
3. 3. The method for fast acquisition of a high dynamic signal on a low track according to claim 2, wherein the number of the multi-path parallel correlators is 20-25 paths; The step size is 20-25 half chips.
4. 4. The method of claim 3, wherein the BPSK pseudocode is slid by a step amount within a specified time after each correlation operation.
5. 5. The method for rapid acquisition of a low-rail high dynamic signal according to claim 1, wherein the frequency secondary searching step comprises sequentially applying 3-5 different unidirectionally varying doppler frequency compensation values.
6. 6. The method for fast acquisition of high dynamic signals on a low track according to claim 1, wherein in the time-division parallel correlation step, when a correlation peak is detected, it is determined that the correlator output exhibits a pattern in which a large value and a small value alternate, then it is determined that the current period is in a BPSK period, and it is confirmed that the code phase acquisition is successful.
7. 7. The method for rapid acquisition of a low-rail high dynamic signal according to claim 1, further comprising the step of threshold decision: In the time-sharing parallel correlation step, a first detection threshold value is set for the detection of a correlation peak; in the frequency secondary searching step, a second detection threshold is set for confirming that the final acquisition is successful.
8. 8. A fast capture system for low-rail high-dynamic signals, comprising a processor and a memory, said memory having stored thereon a computer program which, when executed by the processor, implements the steps of the fast capture method for low-rail high-dynamic signals as claimed in any one of claims 1 to 7.

Description

Quick capturing method and system for low-rail high-dynamic signals Technical Field The application relates to the technical fields of satellite communication and signal processing, in particular to a method and a system for rapidly capturing a low-orbit high-dynamic signal. Background With the rapid development of low-orbit satellite navigation enhancement technology, how to capture satellite-borne high-dynamic navigation signals has become a focus of academic interest. The composite Code shift keying (Multiple Code SHIFT KEYING, MCSK) modulation mode can effectively improve the text transmission rate by dividing time slots and distributing different signals in each time slot, is expected to be widely applied in the future low-orbit navigation enhancement field, and becomes a key problem how to capture discontinuous signals of the Code period. Currently, conventional signal time domain acquisition methods include a serial sliding correlation method and a parallel correlator method. The purpose of the serial sliding correlation method is to estimate the code phase and doppler shift of the received signal and use these estimates to initialize the tracking loop, a typical BPSK signal acquisition model is shown in fig. 1. The acquisition model can know that the maximum amplitude of the two paths of signals of I, Q can be obtained only when the local pseudo code rate is consistent with the pseudo code rate in the received signal and the local carrier frequency is consistent with the carrier frequency of the received signal with additional Doppler frequency shift. The acquisition of the deduced spread spectrum signal comprises two steps, an estimate of the pseudo code phase offset and an estimate of the doppler shift, respectively. In the conventional time domain sliding correlation method, in the searching process, the code phase stepping amount is half a chip, the doppler shift stepping amount is a doppler shift unit, and then a code phase searching unit and a doppler shift unit form a searching unit in a two-dimensional space, as shown in fig. 2. And when the correlation result of the local code and the pseudo code of the received signal is higher than a preset detection threshold, capturing is completed. The parallel correlator technology means that a plurality of correlators are applied in the capturing process, so that parallel searching of a plurality of code phases can be realized, the capturing speed can be improved, and a capturing principle diagram is shown in the following figure 3. The intermediate frequency signals are mixed to obtain zero intermediate frequency signals, and then a parallel correlator is adopted to perform correlation operation. In fig. 3, 10 parallel correlators are used, 10 code phases can be searched in parallel at a time, the code phase searching speed is changed to 10 times of the original speed, and the effect of searching the code phases in parallel in a small range can be achieved, so that the capturing speed is improved. MCSK signal, MCSK modulation model may be denoted MCSK (U, K, P). The model is mainly determined by 3 parameters, wherein U represents the bit number of each CSK symbol, K represents the divided time slot number, and P represents the time slot number where the data is located. For example MCSK (6,2,1) shows that each CSK symbol represents 6 bits, and is divided into two slots, with data in the odd slots. The slot allocation diagram is shown in table 1 below. TABLE 1 Since the code phase of MCSK signals is not continuous, which presents a great challenge for signal acquisition, conventional time domain acquisition algorithms have not been suitable for such code phase discontinuous signals. In the traditional signal time domain capturing method, although the method is simple, the serial sliding correlation method only can search one code phase at a time, so that the code phase searching speed is slower, and further the frequency step in the frequency domain searching process is caused to be incapable of matching with the high Doppler frequency shift change rate of the low-rail signal, so that capturing failure is caused. Although the parallel correlator method can accelerate the acquisition speed, the parallel correlator method cannot be directly applied to the signal acquisition due to the characteristic of discontinuous signal code phase of the low rail MCSK. Disclosure of Invention The embodiment of the application provides a rapid capturing method and a rapid capturing system for a low-rail high-dynamic signal, which solve the problem that MCSK signal code phases are discontinuous in the capturing process, greatly improve the signal capturing speed and ensure the success rate of capturing the low-rail high-dynamic MCSK signal. The embodiment of the application provides a method for rapidly capturing a low-rail high-dynamic signal, which comprises the following steps: Receiving an intermediate frequency signal, searching a code phase by carrying out corre