深空伪码测距中复合码性能的分析与研究

摘要

深空伪码测距系统中复合码的选择影响到系统的无模糊距离、测距精度、捕获时间和硬件实现方法．针对深空伪码测距系统中常用的测距码进行仿真、分析、比较与研究，包括复合码的频谱特性、周期、直流分量、码钟衰减、捕获时间和测距抖动误差等．利用同相相关系数和非同相相关系数的信号空间图分析复合码的捕获时间性能；采用同相中相积分环作为码跟踪环，利用其线性环路模型分析测距系统的抖动误差性能；进而分析半正弦成型和方波成型对系统的捕获时间和测距抖动误差的影响．通过研究和分析认为，在深空测控测距中，一种比较适用的测距方式是选择T4B作为伪码测距系统的测距码，基于DDS原理产生任意码片移位的伪码序列，采用半正弦成型调制方式和半正弦匹配滤波接收技术，利用同相中相积分环进行伪码的跟踪．%The selection of ranging codes influences many parameters of the deep space ranging system, such as the ambiguity distance, ranging resolution, acquisition time and hardware implementation, etc. In this paper, several ranging codes commonly used in the deep space ranging system are simulated, analyzed, compared and studied, especially for their spectrum, cycle, DC, ranging clock attenuation, acquisition time and ranging jitter error. The signal space figure method with in-phase/out-phase correlative coefficient is used to analyze the acquisition time. And in-phase/mid- phase integration loop, as a chip tracking loop, is applied to analyze the ranging jitter error. Also, the influences of acquisition time and ranging jitter error due to sinusoidal pulse shaping and squarewave pulse shaping are analyzed. Through the research and analysis, some results are proposed as that T4B is chosen as ranging code in deep space ranging system, DDS method is selected to create arbitrary chip phase shift, sinusoidal pulse shaping modulation and sinusoidal pulse shaping matched filter scheme are adopted, and in-phase/mid-phase integration loop is applied to track the ranging code.