Abstract

The paper is a study of the Global back-projection algorithm (GBP) known to be a fundamental time domain algorithm for image retrieval in Synthetic Aperture Radar (SAR). Although frequency domain algorithms are convenient to use and understand yet they have some inherent drawbacks and require various compensation techniques. As a time-domain algorithm, GBP possesses inherent advantages such as perfect motion compensation, unlimited scene size, wide bandwidth and ability to handle long integration angles. Although GBP reproduces SAR images on pixel-to-pixel basis, the processing time for GBP is reduced significantly. For GBP, the number of operations required to process an N×N SAR image with N aperture positions is proportional to N³. A detailed explanation on how to implement GBP in Matlab in order to retrieve a SAR image is provided. Matlab provides various in built functionalities as well as image processing toolbox which assists in performing signal processing operations along with an easy evaluation of the result. Since the image construction takes place on a pixel to pixel basis a lot of computations are involved, however we obtain a high quality image. Also many of the frequency domain algorithms although quick, suffer from distortion due to motion. But GBP possesses inherent motion compensation techniques which provides images of high accuracy. Thus the objective of the project to prove the efficiency of the time domain algorithms as an effective alternative to frequency domain algorithm will be substantiated using a few simulations.