与高波段窄带SAR相比,UWB SAR孔径长,多普勒调频率有较大不同.针对UWB SAR中多普勒调频率的不同形式,研究了一种大测绘带条件下UWB SAR的运动补偿方法,即通过直线拟合求出不同距离单元内的多普勒调频率,然后,不再进行运动参数分离,而是直接进行运动补偿.实测数据处理结果验证了该方法的有效性.

Motion compensation is a key factor in SAR imaging. Generally speaking, there are two kinds of motion compensation. One is based onmeasured data and the other is based on echo data. In this paperwe focus on the latter one. The Doppler rate is an essential parameter in the process of the motion compensation; the instability in both forward velocity and acceleration ofaircraft is regarded as vibrations of theDoppler rate. In the high-frequency band SAR, synthetic aperture is narrow and the hypothesis is tenable thatthe slantrange is longer than the lengthof synthetic aperture. Basing on thehypothesis, theDoppler rate in the high-frequency band SAR has nothing to do with the position of the objec.t Thus the formation of theDoppler rate is comparatively simple, and the motion compensation is easy to operate. However, in UltraW ide Band Synthetic Aperture Radar (UWB SAR), the length of synthetic aperture is relatively long, so that the hypothesis that the slant range is longer than the length of synthetic aperture is unreasonable. In themeantime, theDopplerrate in thehigh-frequency band SARmatterswith the position of the objec.t Due to the above reasons, we need to re-analyze the formation of theDoppler rate inUWB SAR and study new motion compensation. Outof this aim, the paper tentatively studiesmotion compensation ofUWB SAR inwide swath. Firs,t We obtain the Doppler rate of different range from linear fitting, and then compensate the phase error directly instead of separating the motion parameters from Doppler rate. In the section ofexperimen,t in order to verify the theoreticalpar,t according to the simulated data,a quantity analysiswasmade on the difference of theDopplerrate in the shortand long pole ofmapping band respectively. Then based onUWB SAR s echo data of AircraftY7and following the theoretical instruction stated in the former par,t we make motion compensation successfully. Using themethod ofdirectaveragewe get the result images. Finally, a comparison ismade between the results obtained from two kinds ofmotion compensation. It turns out that themethod used in this paper is effective.