Design and implementation of wideband digital chirp pulse generator for fine resolution SAR image

Abstract

Wideband chirp pulse generation technology is the prerequisite of various imaging radars and target identification algorithms. The waveform generated by digital systems is much better repetition and coherency. Nevertheless, there still exist some difficulties to directly generate pulse signals with absolute large bandwidth by digital technology because the speed of current digital devices is limited. In this thesis, we present the simulation results of image with various bandwidth of chirp pulse and design two kind of digital chirp pulse generator called AWG and DDS technology. The bandwidth of AWG chirp pulse generator is 300MHz to 500MHz in digital chain. The linear FM waveform values also are generated for the sine look up table. Second one is DDS chirp pulse generator. We designed and implemented 300MHz wideband DDS chirp pulse generator. If we use analog technologies such as orthogonal modulator or double frequency chain circuits, the bandwidth of chirp pulse is extended 600MHz to 1000MHz. Implemented wideband digital chirp pulse generator can be used for the fine resolution imaging SAR system. It is possible to make 25cm to 50cm range resolution image.