# Real-Time DBS Algorithm Based on CZT

## The Modification of Traditional DBS Algorithm.

According to Sect. 4.2.1, the image proceeded by DBS algorithm is a false image in the azimuth frequency domain. Therefore, in the WAS mode, the GMTI is operated in the image domain, and DBS algorithm is highly important in the GMTI performance.

In conventional DBS imaging algorithms, RCM is neglected to simplify imaging process since azimuth synthetic time within each azimuth processing window is so short that RCM is negligible. As the increasing demand of azimuth resolution, RCM correction process is induced into DBS algorithm. In these modified algorithms [10], Doppler centroid is estimated in each azimuth processing window. However, Doppler centroid estimation algorithms, such as energy balancing method and entropy minimization method, induce complicate operations, such as data transpose, correlation and iteration, which make DBS imaging not applicable to real-time processing. In addition, if Doppler centroid is not correctly estimated, RCM cannot be perfectly corrected.

Besides the modification of the introduction of RCMC, article [11] also proposed to dechirp the azimuth signal so as to increase the azimuth resolution. However, according to our analysis and simulation, the azimuth second-order phase error is negligible, and the deramping operation is contrary to the efficiency of the DBS algorithm.