无源相干脉冲雷达时间同步误差影响分析

The impact of time synchronization error on passive coherent pulsed radar system

在无源相干脉冲雷达系统中,由于直达波信号的起伏,难以实现对其脉冲重复频率实时且精确地估计,导致脉冲重复频率与采样时钟之间总是存在时间同步误差,很难满足脉冲间相参采样的条件.文中首先通过对无源相干脉冲雷达系统的中频采样过程进行建模,推导了脉冲间相对采样时刻的变化周期与时间同步误差的关系,然后定义了归一化干扰功率来分析时间同步误差对无源相干脉冲雷达系统相参处理输出的影响.在此基础上,推导了脉冲间相对采样时刻的差服从均匀分布和Gauss分布时的归一化干扰功率,并给出了相应的仿真结果.同时,推导了存在时间同步误差时Doppler频率估计的理论误差,并给出了相对采样时刻变化周期不同时Doppler频率估计的仿真实例,验证了理论分析的正确性.

Passive bistatic coherent radar system operates with distinct non-cooperative transmitter and receiver located at different sites. In such spatial separation, the receiving system needs to independently solve the problem of time and phase synchronization via direct-path signal. The impact of time synchronization error was explored and solved in passive bistatic coherent radar. The common model of digital sampling process is introduced to illustrate the effect of time synchronization error （TSE）. The periodicity of relative sample instant variation of each pulse is deduced. Then, normalized interference power （NIP） is defined to evaluate the potential impact of TSE. The NIP expressions are derived when the difference between the adjacent relative sample instant is uniform distribution or Gaussian distribution. It is found that there are new spurious frequency components and the detection performance is decreased in the case of asynchronous sampling. At the same time, the analytical Doppler frequency bias expression caused by TSE is presented. Theoretical results are confirmed by simulation in the cases of different periods of relative sampling instant.