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摘要:
针对传统GPS C/A码延迟测高方法测高精度低和互相关测高方法时延波形信噪比低的问题，研究了基于半无码的P（Y）码自相关海面测高方法。首先，通过理论测高精度模型，对比分析了C/A码和P（Y）码的测高精度；然后，描述了L1、L2双频反射信号基于半无码的P（Y）码自相关处理架构，并论述了测高模型和L1、L2双频电离层时延误差修正方法；最后，利用模拟的L1、L2反射信号对比分析了基于半无码的P（Y）码自相关、C/A码自相关以及信号互相关方法的海面测高精度。结果表明：相比于C/A码自相关和信号互相关测高精度，基于半无码的P（Y）码自相关的测高精度分别提高了3.97倍和1.47倍。
Abstract:In this paper, the semi-codeless based P(Y) code autocorrelation sea surface altimetry method was studied due to the fact that the conventional GPS C/A code delay altimetry method is less precise, and that the signal-to-noise ratio of delay waveform in interference altimetry method is low. First, the height measurement accuracy of the C/A code and P(Y) code was compared and analyzed through theoretical model for describing the height measurement accuracy. Then, the architecture of semi-codeless based P(Y) code autocorrelation processing for L1 and L2 dual-frequency reflected signals was described. Meanwhile, the altimetry model and dual-frequency ionospheric time-delay error correction methods are discussed. Finally, using simulated L1 and L2 reflection signals, the measurement accuracy is compared and analyzed regarding the proposed method, C/A code autocorrelation method and signal cross-correlation method. The results show that the accuracy of the proposed method is 3.97 times and 1.47 times higher than that of the C/A code autocorrelation method and signal cross-correlation method, respectively.
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Key words:
- semi-codeless /
- P(Y) code /
- sea surface altimetry /
- dual-frequency /
- ionospheric delay correction
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图 1 不同海面粗糙度条件下的GPS C/A码与P(Y)码反射信号归一化相关功率曲线
Figure 1. Curves of normalized correlation power of GPS C/A code and P(Y) code reflected signals under different sea surface roughness conditions
图 2 不同ΔSNR条件下GPS C/A码与P(Y)码信号测高精度的比值随海面粗糙度的变化
Figure 2. Variation of ratio of GPS C/A code to P(Y) code signal altimetry precision with sea surface roughness under different ΔSNR conditions
图 3 基于半无码的P(Y)码自相关测高方法框图
Figure 3. Block diagram of semi-codeless based P(Y) code autocorrelation altimetry method
图 6 3种测高方法处理模拟信号得到的高度测量结果
Figure 6. Analog signal processing results of three altimetry methods
表 1 反射信号仿真参数
Table 1. Reflected signal simulation parameters
参数 数值 机载飞行高度/m 600 卫星高度角/(°) 30 采样频率/MHz 58 相干积分时间/ms 1 非相干累加次数 1 000 风速/(m·s-1) 3 
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表 2 3种测高方法处理模拟信号得到的高度均方根误差
Table 2. Height mean square root errors obtained by analog signal processing using three altimetry methods
测高方法 均方根误差/cm 基于半无码的P(Y)码自相关测高 36.220 2 信号互相关测高 89.373 9 C/A码自相关测高 180.040 0
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