Implementation of CORDIC based DCT on FPGA for SAR Image Compression
Sudhakara Reddy · 2014
At present, the Synthetic Aperture Radar (SAR) technologies are rapidly developing in various countries and enhancing the unique and variable functionality of observing the global earth and its environmental characteristics. The SAR is a form of a Radio Detection and Ranging (RADAR) system which can acquire data with very high resolution. At present, a huge amount of SAR raw data compression is required to store and the purpose of statistical data analysis. In this regard, two encoding techniques are generally used for SAR. First, direct encoding in spatial domain and second, transform encoding in transform domain. In transform domain, we use discrete cosine transform (DCT) for efficient coding cum compressing. The DCT based compression techniques play an important role in today's digital SAR image compression applications. The DCT is a fast transform, perform real operations using low complexity arithmetic and has very good energy compaction. Implementing DCT using CORDIC algorithm reduces the number of computations while using shift-and-add operations during processing. The proposed architecture is simulated and synthesized by busing Xilinx's software and the same was implemented on targeted FPGA. The RADAR means Radio Detection and Ranging which is a communication medium to detect objects which are at a distance that cannot be observed visually. The RADAR provides a capability of detecting objects over great ranges through air at night and in poor weather. The SAR is a form of RADAR whose defining characteristics is it use of relative motion, between an antenna and its target region. Synthetic Aperture Radar is remote sensing system which is used for earth observation. The SAR system has the ability to take images in all weather conditions and darkness. With the improvement of SAR technology larger areas are being imaged and the resolution of the images has increased. This causes larger images to be transmitted and stored (1). The SAR images carry information in low frequency bands as well as high frequency bands. The SAR images have larger dynamic range and higher entropy. The higher entropy and large dynamic range of SAR images results in very low compression ratio when lossless compression techniques are used. Thus, if a small amount of information loss is