并行高采样实现PN码捕获的井下扩频测距方法

Underground Spread Spectrum Ranging Algorithm With a Parallel High Sampling Technology of PN Code Acquisition

摘要:

在扩频测距技术中,伪随机(Pseudo-Noise)码捕获时间长,扩频信号需要高带宽信道,井下多径效应还会引起PN码相位延迟,因而使得扩频测距技术难以在煤矿井下应用;为了将扩频测距技术应用于井下,设计了一种并行的PN码同步精测算法,利用FPGA高速的并行处理能力,开辟L-1条相位彼此相差一个PN码片的相关通道,在各相关通道中分别对扩频码调制的数字基带信号相关运算后进行高频率采样,大幅度提高了信号处理带宽,能够在粗同步的基础上直接得到更高的时间分辨率;仿真结果表明,所提出的方法能够抑制井下严重的多径干扰,能将测距PN码所占带宽限制在50 MHz以下而测距精度达到1 m以内,是适应煤矿井下特殊环境的一种高效扩频测距方法。

Abstract:

Spread spectrum ranging technology requires high bandwidth occupation and long duration of PN code acquisition,furthermore,its PN code phase delay problem is serious because of multi-path effect. These factors make it difficult to apply spread spectrum ranging technology in underground coal mines. In order to resolve the awkward situation,a parallel algorithm for PN code precision synchronization was designed making full use of FPGA processor's excellent parallel processing capability . In FPGA,L-1 correlation channels which have a PN code phase differences from each other are allocated,digital baseband signal modulated by PN code is sampled with high sampling after it correlates with the local PN code. This high sampling frequency can greatly improve signal processing bandwidth,so a high time resolution can be obtained only through the coarse synchronization. Experimental results of simulation show that the performance of proposed method can be applied efficiently in coal mine,with high suppression performance over multi-path effect,and the accuracy error of ranging is less than 1 m while the bandwidth occupation of PN code is no more than 50 MHz.