Spread spectrum CPM signal capturing method with modulation index h being more than 1 and being half integer

Abstract

In the capturing process of a CPM signal with a modulation index h being more than 1 and being a half integer, due to the fact that a correlation function of the CPM signal has the multi-peak characteristic, the problem of false capturing can happen, and the spread spectrum CPM signal is captured by applying a Bump Jump algorithm to correlation function peak detection of the spread spectrum CPM signal with the modulation index larger than 1. A secondary peak detection method of the spread spectrum CPM signal based on collision jump is provided aiming at the influence of the low signal-to-noise ratio on zero point dislocation of main detection and auxiliary detection functions, when a receiver detects a secondary peak, judgment and processing are carried out, an estimated code phase jumps towards the direction of a main peak, and finally the position of the main peak is determined. Verification is carried out on a Matlab platform, a detection algorithm based on collision jump is suitable for capture of spread spectrum CPM signals, the detection performance of the algorithm is improved by about 4 dB compared with that of a Bump Jump algorithm under the condition of a low signal-to-noise ratio, and capture of the spread spectrum CPM signals under the condition of the low signal-to-noise ratio can be more effectively achieved.

Description

technical field [0001] The invention belongs to the field of digital communication, and specifically relates to solving the problem of wrong capture caused by the multi-peak characteristic of the correlation function in the capture of the spread spectrum CPM signal with the modulation index h>1 and h being a half integer. Background technique [0002] The global navigation satellite system can provide all-weather, continuous and real-time high-precision geographic location information and services such as navigation, timing information, and short packet communication. Among them, the Beidou navigation and positioning system (BDS, Beidou system) is independently developed and constructed by my country. The B1C signal is the main signal of a new generation of civilian signals adopted by the Beidou satellite navigation system, and is modulated by a binary offset carrier (BOC) signal. The BOC modulated signal ensures a higher second-order moment of power spectral density due ...

AI Technical Summary

Problems solved by technology

The acquisition problem is the search problem of the code phase and Doppler frequency shift. The serial search acquisition algorithm uses two-dimensional search for the code phase delay and Doppler frequency shift to capture the signal, although the consumption of hardware Small, but the capture efficiency is not high; the parallel code phase search algorithm can traverse all the code phases at a certain Doppler frequency point after one calculation, but this algorithm is difficult to adapt to the situation of many Doppler frequencies; The parallel frequency domain search algorithm takes advantage of the computational advantages of FFT to search all frequencies simultaneously in the code phase, which improves the search efficiency, but is limited by the length of the pseudo code

[0004] The key to capture is to calculate the correlation function of the received signal, but the correlation function of the spread-spectrum CPM signal with a modulation index h>1 has multi-peak characteristics, which will lead to false capture, which will reduce the detection performance, but has always been , there is a lack of research on the capture of spread spectrum CPM signals with modulation index h>1

For the problem of multi-peak characteristics of the autocorrelation function in signal capture, Julien O et al. adopted the ASPect method to realize the unambiguous capture of Sine-BOC(n,n), and Calmettes et al. used the unambiguous capture method of the commonly used BOC signal However, these methods have strict requirements on the signal structure and are only suitable for signals with subcarrier modulation such as BOC signals. Although spread spectrum CPM signals have similar spectrum characteristics and multi-peak characteristics of autocorrelation functions as BOC signals, But he does not perform subcarrier modulation, so these methods cannot be used

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