The WAS GMTI mode has the advantages of wide-swath, real-time processing, and multiple revisits. Therefore, it is an effective mode to indicate the ground moving targets in the SAR system. The advantages of mechanic scanning mode include simple system structure, low cost and single channel. The main topic of this chapter is focused on the mechanic scanning mode.
First of all, the working scheme of the mechanic scanning mode and the principle of the DBS imaging algorithm have been introduced. To obtain the constant sharpening ratio, a new system design scheme has been presented, which does not increase the complexities of the system and the signal processing.
Secondly, a novel real-time DBS algorithm based on CZT has been proposed. The proposed algorithm has two advantages: (1) it simplify the modified DBS processing by circumventing Doppler centroid estimation, which makes it applicable to real-time project; (2) resolution loss caused by Doppler centroid estimation error is avoided.
At last, based on real SAR data of WAS GMTI mode, a GMTI and parameter estimation algorithm has been presented based on multiple revisits. By using the multiple revisits of the same observation area, the location of the moving target is different in each image, and the motion parameters can be estimated from the location changes. However, this algorithm still faces the shortcomings that it is not suited for real-time processing.