时频差精度的时变性影响及补偿估计方法

Effect of time-varying characteristics on TDOA/FDOA accuracy and compensation estimation method

到达时差(time difference of arrival,TDOA)和到达频差(frequency difference of arrival,FDOA)/频差无源定位体制中,定位精度取决于时频差参数的估计精度。针对微纳卫星定位系统中时变参数估计性能随累积时间增加会出现恶化的问题,分析了相对频率扩展(relative frequency companding,RFC)对频差方向复模糊函数(complex ambiguity function,CAF)峰的扩展效应,推导了无补偿的RFC对频差估计精度的影响,给出频差估计精度的衰减因子及最优累积时间。在理论分析的基础上,提出一种时变补偿的时频差估计方法,用以克服时变特性引起的时间及频率扩展效应。仿真结果表明,该方法可有效消除参数估计精度的损失,估计精度逼近非时变参数的理论极限。

The estimation accuracy of time difference of arrival（TDOA）and frequency difference of arrival（FDOA）is crucial to the passive location system using these parameters.In the micro/nano satellite location system,the estimation performance of these parameters will be deteriorated by the cumulative time increasing.In order to solve the problem,the expansion effect of relative frequency companding（RFC）on the complex ambiguity function（CAF）in FDOA direction is analyzed,then the impact of uncompensated RFC on the FDOA estimation accuracy is derived,and then the degradation factor of FDOA estimation accuracy and optimum cumulative time is presented.On the basis of the theoretical analysis,a method of TDOA/FDOA estimation based on time varying compensation is also proposed,which can overcome the time and frequency expansion effect caused by time-varying characteristics.Simulation results show that the proposed method can eliminate the estimation accuracy loss effectively,and the parameter estimation accuracy can approach the non-time-varying theoretical limit.