﻿ 基于块平均预处理的GNSS-R延迟映射处理方法
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GNSS-R delay mapping processing method based on block averaging pre-processing
WANG Feng, YANG Dongkai , LI Weiqiang, ZHANG Yanzhong
School of Electronics and Information Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Abstract:To improve signal-to-noise ratio of global navigation satellite system reflected signals, a method of processing navigation satellites reflected signal based on block averaging pre-processing (BAP) was presented, which divided the received signals into blocks with period of pseudocode and achieved the mean values of blocks by superposition and averaging, and then performed the correlation process for the mean values. On the basis, the model of reflected signal which processed by BAP was theoretically analyzed; the mathematical expression of processing gain of signal reflected by specular point and correlation power model were derived; computational complexity of this method was compared with one of traditional method. The conclusion is that this method conducts the spatial filtering for reflected signals, improves signal-to-noise ratio and effectively reduces computational complexity. At last, a software receiver was developed to process coastal raw GPS data collected. The results show that when the BAP time are 2, 5, 10, 15 and 20ms, the method improves about 3.5, 6.7, 10.2, 10.6 and 10.4dB on signal-noise ratio of peak and reduces the processing time by about 2.2 times, with BAP being 10ms, compared with the traditional method.
Key words: global navigation satellite system (GNSS)     reflected signal     block averaging     signal processing     signal-to-noise ratio (SNR)     processing time

1 导航卫星反射信号模型

 图 1 观测区域反射示意图 Fig. 1 Diagram of reflection in observation region

2 基于BAP的反射信号处理方法 2.1 基于块平均预处理的反射信号模型

 图 2 L ms反射信号的块平均预处理示意图 Fig. 2 Block averaging pre-processing diagram of L ms reflected signals

, 则式(4)可表示为

HL(f)为块平均预处理响应函数,其表达式为

 图 3 块平均预处理的幅频特性 Fig. 3 Amplitude-frequency characteristics of block averaging pre-processing
2.2 基于块平均预处理的反射信号处理结构

 图 4 基于块平均预处理的反射信号处理结构图 Fig. 4 Structure diagram of processing reflected signals based on the block averaging pre-processing

2.3 基于块平均预处理的反射信号一维相关功率

3 性能分析 3.1 镜面反射点处理增益

 L m Gspe/dB 与传统方法增益差/dB 1 1 000 50.0 0 2 500 51.4 1.4 5 200 53.3 3.3 10 100 54.6 4.6 20 50 55.8 5.8
3.2 计算复杂度

 计算类型 L=1 L>1 缩小倍数 乘法 2MS1(N+1) 2MS2(N+1) S1/S2 加法 MS1(2N－1) NS2(2M+L－1) S1/S2(1+xL/2M)
4 岸基数据处理

 图 5 反射信号一维时延相关功率 Fig. 5 One-dimensional delay correlation power of reflected signals

 L 峰值功率/dB 底噪/dB 信噪比/dB 1 86.7 73.9 12.8 2 90.1 73.8 16.3 5 93.5 73.9 19.5 10 97.0 74.0 23.0 15 97.4 74.0 23.4 20 97.1 73.9 23.2

 处理数据长度/ms 软件处理时长/s 缩短倍数 L=1 L=10 1 000 10.2 4.6 2.22 60 000 609.2 287.5 2.12 120 000 1 235.2 562.8 2.19
5 结 论

1) 在伪码自相关函数和sinc函数空域滤波的基础上,增加了一次空域滤波.

2) 在一维时延相关功率输出率恒定的条件下,减小了非相干累加次数,进而减小平方损耗,有效提高了镜面反射点反射信号增益.

3) 降低计算复杂度的倍数近似为块平均预处理的分块数.

1) 有效提高了反射信号一维相关功率的峰值信噪比,对于存在导航电文的信号,块平均预处理时间受到限制,当与导航电文比特位宽相近时,峰值信噪比增加受到限制,甚至开始下降,对于无导航电文存在的信号,块平均预处理时间可以设置较长.

2) 有效缩短了处理等时长数据的时间,本文中的处理时长缩短了近2.2倍.

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#### 文章信息

WANG Feng, YANG Dongkai, LI Weiqiang, ZHANG Yanzhong

GNSS-R delay mapping processing method based on block averaging pre-processing

Journal of Beijing University of Aeronautics and Astronsutics, 2015, 41(10): 1943-1949.
http://dx.doi.org/10.13700/j.bh.1001-5965.2015.0040