基于“北斗”差分的双基SAR高精度时频同步方法

A High Precision Time-Frequency Synchronization Method of Bistatic SAR Based on Differential Beidou

为了满足分布式平台协同探测和双基地合成孔径雷达(Synthetic Aperture Radar,SAR)目标成像对时频同步的高精度应用需求,提出了一种基于“北斗”导航卫星观测单差的时频同步方法。该方法基于伪距单差计算得到平台间的相对钟差,并通过载波相位观测单差的前后历元差消除单差整周模糊度,计算得到相对频率误差。静态实测和动态模拟测试结果表明,该方法可以实现固定时间同步误差优于5 ns,线性时间同步误差优于2×10^(-3)ns/s,二次时间同步误差优于10^(-6)ns/s^(2),固定频率同步误差优于0.01 Hz,线性频率同步误差优于10^(-5)Hz/s的精度,满足实际工程应用的要求。在该时频同步方法的基础上,开展了双基SAR目标成像质量仿真分析,验证了算法的可用性,可以保证分布式协同系统的动态、实时和高精度时频同步应用。

In order to meet the high precision application requirements of time-frequency synchronization for collaborative detection of distributed platforms and bistatic synthetic aperture radar(SAR)target imaging,the authors propose a high-precision time-frequency synchronization method based on single difference of Beidou navigation satellite observation.The method calculates the relative clock difference between platforms based on the single-differenced pseudo-range,and calculates the frequency difference by eliminating the cycle ambiguity with the epoch difference of the single-differenced carrier phase.Static field test and dynamic simulation test results show that the fixed time synchronization error between platforms calculated by the proposed algorithm is less than 5 ns,the linear time error is less than 2×10^(-3)ns/s,the second-order time error is less than 10^(-6)ns/s^(2),the fixed frequency synchronization error should is less than 0.01 Hz and the linear frequency error is better than 10^(-5)Hz/s,which meets the requirements of practical engineering applications.According to the time-frequency synchronization method,simulation of bistatic SAR target imaging quality is carried out.The results verify the availability of the algorithm,and it can ensure the dynamic,real-time and high-precision time-frequency synchronization application of the distributed cooperative system.