The Research For FMCW SAR Imaging Algorithm And Motion Compensation

Synthetic aperture technology solves the problems of radar dependence on the RF antenna with using a single antenna motion to synthetic equivalent large aperture antenna.But with high power consumption,high cost and big spce,the pulse SAR can not widly use in every field.Frequency modulated continuous wave synthetic aperture radar(FMCW SAR),obtained high resolution in range direction with continuous wave technology,obtained high azimuth resolution with the synthetic aperture technology?It not only improve the resolution,but also to meet the development needs of airborne small platform of low power consumption,miniaturization,what's more,it has been widely used in airborne small platform.In this thesis,the imaging algorithm for FMCW SAR,range Doppler algorithm(RD)and wave-number domain algorithm are researched based on the pulse SAR,and derived two algorithms of imaging process according to the FMCW SAR signal expression,and the performance of the various aspects of the two algorithms were analyzed.RD algorithm was not suitable for airborne small platform because of the high demands on the oblique angle and beam angle while the wavenumber domain algorithm can meet the precision processing of oblique angle.Based on the FMCW SAR imaging algorithm,this paper aimed at the problem of small platform motion compensation of airborne.In this paper,we get the slant range error through the analysis of imaging geometry model of nonideal motion state of FMCW SAR,and then decomposed it into first motion compensation(distance independent)and second motion compensation(distance dependent).The wavenumber domain algorithm converse the echo signal from the time domain to the two-dimensional frequency domain directly,and make a STOLT interpolation in the two-dimensional frequency domain,but the two-dimensional signal on distance and azimuth are focused after interpolation,which made the two step motion compensation method cannot be applied in the algorithm.In this paper,the improved STOLT interpolation algorithm,which makes signal after interpolation in azimuth direction not focused,and proposed a motion compensation method based on the wavenumber domain algorithm.The simulation analysis proved that,the algorithm can well compensate the error caused by the instability by loading machine.