导航卫星星地双基SAR时频同步误差估计方法

doi:10.19665/j.issn1001-2400.2023.02.005

摘要/Abstract

摘要：

为验证长合成孔径时间下地球同步轨道合成孔径雷达对地成像的机理,采用北斗3号IGSO导航卫星作为照射源,地面静止接收的星地双基构型进行等效性验证。针对导航卫星信号特点和星-地双基合成孔径雷达面临的时间频率同步难题,提出了一种基于回波数据估计导航卫星测距码延迟误差,并进行误差修正的星地双基地合成孔径雷达回波数据时频同步误差估计方法。该方法首先根据导航卫星脉冲重复频率对一维直达波信号和反射波信号进行了二维划分,保留了整个采集信号的完整性,通过直达波信号距离向匹配滤波获得非理想采样环境下正确的峰值位置序列,并利用此峰值位置序列完成直达波信号和反射波信号的时间同步误差补偿以及本地测距码的修正,解决了北斗3号IGSO导航卫星星地双基合成孔径雷达成像过程中存在时间同步后距离脉压信号包络分布与理论推导模型失配的问题;然后利用修正后的本地测距码对直达波信号匹配滤波获得直达波峰值相位矢量;最后利用此峰值相位矢量对反射波信号进行频率误差补偿和成像处理。实测数据的处理结果验证了所提方法的有效性。

关键词: 地球同步轨道合成孔径雷达, 北斗3号导航卫星, 双基合成孔径雷达, 测距码, 时频同步

Abstract:

In order to verify the mechanism of GEO SAR imaging with a long synthetic aperture time,the equivalence verification is executed by satellite-to-ground bistatic configuration,which is composed of the Beidou 3 IGSO navigation satellite and the ground-stationary receiver.According to the signal characteristics of navigation satellites and the time-frequency synchronization problem of the satellite-to-ground bistatic SAR,based on the echo data a time-frequency synchronization error estimation method of satellite-ground bistatic SAR echo data is proposed to estimate the delay error of navigation satellite ranging code and correct the error.First,the one-dimensional direct wave signal and the reflected wave signal are divided into two dimensions according to the pulse repetition frequency of the navigation satellite,which preserves the integrity of the whole collected signal.The correct peak position sequence under non-ideal sampling environment is obtained by the matching filter on the range of the direct wave signal,and then the peak position sequence is used to complete the time synchronization error compensation of the direct wave signal and the reflected wave signal,and so with the correction of the local ranging code,which solves the problem of the mismatch between the envelope distribution of the distance pulse pressure signal after time synchronization and the theorectical model in the satellite-ground bistatic SAR imaging of the Beidou-3 IGSO navigation satellite.Second,the corrected local ranging code is used to obtain the direct wave peak phase vector by matching filtering the direct wave signal.Finally,the peak phase vector is used to perform frequency error compensation,followed by the bistatic SAR imaging processing of the reflected wave signal.The processing results of the measured data verify the effectiveness of the proposed method.

Key words: GEO SAR, Beidou 3 Navigation Satellite, bistatic SAR, ranging code, time-frequency synchronization

中图分类号:

TN957

遆晶晶, 索志勇, 王婷婷, 赵秉吉, 张乐茹. 导航卫星星地双基SAR时频同步误差估计方法[J]. 西安电子科技大学学报, 2023, 50(2): 42-53.

TI Jingjing, SUO Zhiyong, WANG Tingting, ZHAO Bingji, ZHANG Leru. Time-frequency synchronization error estimation method for the satellite-to-ground bistatic SAR for a navigation satellite[J]. Journal of Xidian University, 2023, 50(2): 42-53.

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指标	理论值	实测值	展宽/%
方位向分辨率/m	4.193 2	4.228 2	0.83
地距向分辨率/m	21.210 7	21.404 2	0.91