微型测控应答机再生测距码跟踪精度研究

Study on the Tracking Accuracy of Regenerative Ranging Codes Used in Micro-Satellite Transponders

微小卫星的星载测控应答机由于功率和天线增益受限,测距误差较大.而再生伪码测距能显著减少下行链路的噪声,从而提高伪码跟踪精度.针对最新的再生测距码,利用线性分析的方法,对伪码跟踪环的理论均方定时误差进行了推导,并对这些测距码的跟踪性能进行了仿真和比较.与理论值不同的是,环路的实际跟踪性能由于VCO相位噪声的存在,不是环路带宽的单调函数.因此,需要根据信噪比条件设置相应的最佳带宽,以得到最佳的跟踪性能.与理论情况相比,各测距码实际环路跟踪性能的差异有所减小.

Due to limited power dissipation and antenna gain of transponders in micro-satellites, the ranging error is quite large. Regenerative pseudo-noise ranging, however, can substantially reduce the noise in the returned ranging signal, thus improve code tracking accuracy. With respect to several newly proposed regenerative PN ranging codes, the mean-square timing error of the chip tracking loop is derived using linear analysis, and simulation and comparison of tracking performance is made for these codes. The practical loop tracking performance is not a mon- otone function of loop bandwidth due to VCO phase noise, which is different from the theoretical case. Thus, the loop bandwidth settings need to be optimized to obtain the optimal tracking performance. The differences of the practical tracking performance of different ranging codes are less than the theoretical ones.