一种用于合成孔径高度计的开环抗混叠滤波方法

An Open Burst Anti-aliasing Filtering Method for Synthetic Aperture Radar Altimeter

开环工作模式是一种交替收发脉冲的合成孔径高度计工作模式,该模式相比于Sentinel-3等卫星高度计的闭环工作模式在单位时间内可获得更多的独立脉冲数,进而提高测距精度。但由于开环模式的脉冲重复频率小于多普勒带宽,其方位向多普勒频谱存在混叠,使得产生的多视回波畸变,降低测距精度。通过研究用合成孔径信号处理过程中距离弯曲与混叠频率的对应关系,提出一种基于多视波束堆栈处理的开环抗混叠滤波方法,对多视波束堆栈进行滤波处理,有效解决了开环模式方位向混叠效应。通过仿真验证,该方法能有效提高测距精度。在2 m有效波高条件下,采用本文提出的开环抗混叠滤波方法的1 Hz测距精度由0.7 cm提高到0.6 cm,提高了14%。

The open burst mode is a kind of Synthetic Aperture Radar(SAR)altimeter operation mode with al⁃ternating receiving and transmitting pulses.This mode allows for a greater number of independent pulses in a unit time than the closed burst mode of a satellite altimeter such as the Sentinel-3,thereby improving range pre⁃cision.However,because the Pulse Repetition Frequency(PRF)of this mode is less than the Doppler band⁃width,the azimuthal Doppler spectrum is aliased and the resulting multi-looking echoes are distorted,thus re⁃ducing the range precision.By studying the correspondence between the range curvature and the aliasing frequen⁃cy in the processing of synthetic aperture signals,an open burst anti-aliasing filtering method based on multilooking beam stack processing is proposed to filter the multi-looking beam stack and effectively solve the azi⁃muthal aliasing effect of the open burst mode.The proposed method can effectively improve the range accuracy through simulation.At a significant wave height of 2 m,the 1 Hz range precision of the open burst anti-aliasing filtering method improves from 0.7 cm to 0.60 cm,an improvement of 14%.