透地无线通信的弱信号捕获算法

摘要

Weak signal acquisition plays a crucial role in current field based through-the-earth communication system.In this paper,we improve the traditional sliding correlation acquisition algorithm and propose a weak signal acquisition algorithm in through-the-earth communication.Ultra-Wideband (UWB) pulse shape modulation and high gain spread spectrumis is adopted by communication system,and each chip is modulated as a waveform that is similar to a Gaussian derivative pulse with positive and negative peaks.The received signal is sampled and quantized at a rate of 16 samples per chip and divided into 16 channels according to the time tapping technology.Each channel uses the same PN code correlator for sliding correlation despreading.Sixteen correlation values can be obtained and the difference between the two of them are used as a decision parameter.Both theoretical analysis and simulation results validate that the proposed algorithm shows a great advantage over the conventional one about 7.2 dB.%基于电流场传播的无线透地通信系统,提高接收机灵敏度的关键之一是在尽可能低的信噪比下实现信号的可靠捕获.本文对传统滑动相关捕获算法进行了改进,提出了一种信号捕获新算法.系统采用高增益直接序列扩频及超宽带脉冲基带调制方式,每个码片都调制为一个近似于高斯微分脉冲的正负双峰波形.接收信号以每个码片16个样点的速率采样量化,时分分接为16路信号,各路都用相同的PN码相关器进行滑动相关解扩,每一时刻取其中某两路信号相关量之差作为判决量.理论分析和仿真结果都显示,和传统的滑动相关捕获算法相比,新方法实现可靠捕获所需信噪比可降低7.2 dB.