时域升余弦波形伪码码片跟踪环性能分析

Performance analysis of chip tracking loop using TDRC waveform pseudo-number code

在小码片信噪比(SNR)条件下,用于时域升余弦波形(TDRC)的伪码(PN)时钟恢复的数据转换跟踪环(DTTL)的性能不能满足要求,为此提出了采用新型的码片跟踪环(CTL)用于TDRC伪码时钟恢复,研究发现CTL的环路检测器增益大于DTTL,前者的捕获和跟踪能力强于后者;而且CTL的时钟跟踪能力独立于码片SNR,而DTTL的捕获和跟踪能力与码片SNR相关.对比了在不同码片SNR条件下,DTTL和CTL的均方时序抖动性能,仿真分析表明,在大信噪比条件下,DTTL和CTL的性能一致;在小信噪比条件下,CTL的归一化时序抖动明显好于DTTL.TDRC伪码测控应答机在小码片SNR环境下,采用CTL能获得较高的测距精度.

The traditional data transition tracking loop（DTTL） adopted in pseudo-number（PN） code ranging for clock recovery cannot obtain good performance for time domain rising cosine（TDRC） waveform at small symbol signalto-noise ratio（SNR）.A novel chip tracking loop（CTL） was designed for PN clock recovery.The detection gain of the CTL was bigger than that of the DTTL,so the former＇s capture and tracking performance was better than the latter.And the clock tracking performance of the CTL was independent of the symbol SNR.The mean square timing jitter performance of the CTL and the DTTL for TDRC waveform PN code was analyzed and compared over a wide range of symbol SNR.Analysis indicates that the same performance can be obtained for the DTTL and the CTL at large symbol SNR,while in small symbol SNR environment the performance of the CTL is better than that of the DTTL.In the condition of small symbol SNR,higher ranging precision can be obtained for the CTL TT＆C（tracking,telemetry and control） transponder.