一种GNSS信号捕获中的比特压缩与重构方法

A bit compress and recover approach in GNSS signal acquisition

在全球导航卫星系统(GNSS)双模接收机的信号捕获过程中,采用"多段匹配滤波器(MMF)+快速傅里叶变换(FFT)"的方式实现信号的时频二维搜索,采用非相干累加算法以提高捕获灵敏度,这2种算法在硬件实现中需要占用大量的存储资源。由于现场可编程门阵列(FPGA)芯片的存储资源有限,本文提出了一种比特压缩方法,极大地降低了非相关累加后的随机存取存储器(RAM)资源,比特重构方法对压缩数据做还原处理,保证了数据的精确度。该方法只对强信号的非相干累加结果做压缩,对弱信号结果不做压缩处理。仿真结果表明,该算法在满足0.9的检测概率,0.01的虚警概率下,节省了0.64 Mbit的RAM资源。

In the signal acquisition process of Global Navigation Satellite System(GNSS) double mode receiver, Multi-bank Matched Filter(MMF)+Fast Fourier Transform(FFT) are adopted to realize signal search in time and frequency domain; and un-correlative accumulation is adopted to increase signal acquisition sensitivity. Whereas, these two algorithms cost a lot of memory resources in hardware implementation. A measure of bit compress and bit recover is proposed aiming to the limit of memory resources ofField Programmable Gate Array(FPGA) chip. Bit compress largely cuts the Random Access Memory(RAM) resource after un-correlative accumulation; and bit recover renews the compressed data to guarantee the data precision. This method just compresses the un-correlative accumulation results of strong power signal, but not of the weak signal. Simulation results indicate that this algorithm can save 0.64 Mbit of RAM resource with a detect probability of 0.9 and a false probability of 0.01.