Research On Radar LFM Signal Generation Systems Based On DDS

Waveform design and generation is one of the key techniques in the Radar system. In the paper, the general technique to generate the linear FM signal is introduced firstly. Then the principles of DDS are described. Especially, the distribution and the restraint methods of the DDS spurs are discussed at length.Direct Digital frequency Synthesis, was advanced in early 1970s and has been developing owing to its entirely digital structure. Nevertheless, there still exist some difficulties to directly generate LFM signals with large bandwidth by digital technology because the speed of current digital devices is limited. The single DDS technology can't meet the subject's requirements for the output frequency band and SFDR. The present wide band generators still have to use some analog technologies such as orthogonal modulator.Depending on the theoretical analysis, the author has implemented a wide band LFM signal generator with 120MHz carrier and 20MHz bandwidth according to the scheme mentioned above. The waveforms of output are shown and the analysis of the output and the suggestions for further research are presented.