The Study Of All-digital Generating Technology Of Wideband Radar Signals

Modern high-tech war makes more and more demands on the radar signal generator. It requires that radar signal generator must have wide bandwidth, high stability, fast transition and the ability to generate arbitrary waveform.This paper analyzes various methods of widening the bandwidth of radar signals based on the theory of wideband radar signals generation. It selects the method of adding linear frequency modulation (LFM) within pulse to expand the signal spectrum, and presents an All-digital Generating Technology of Wideband Radar Signals, which combines with DDS technology to design a new wideband radar waveforms generator based on high-speed parallel DDS.The new radar waveform generator uses slower clock to process signal and outputs signal with high speed DAC. The DSP is FPGA, and the high-speed DAC is ADI's AD9739. Through the hardware circuit design and the development of system software, the paper completes a radar waveforms generating system with easy operation and good performance. This paper also tests and analyzes the time domain and frequency domain of the system output signal, then samples data to do pulse compression. The main works of this paper are as follows:(1)This paper expounds the generating theory of wideband radar signal, mainly discusses the most commonly used wideband radar signals—linear frequency modulation signal, and introduces the theory of generating LFM signal with DDS.(2) According to the theory of decimation and interpolation of signal sampling rate conversion, this paper advances a new method of generating wideband radar signals with parallel DDS. The DDS uses slower clock to process signal and outputs signal with high speed DAC.(3)This system is mainly made up of a FPGA and a DAC. The FPGA is Virtex-5 and the DAC is AD9739. According to the system the paper designs a software to control over the system with Matlab by PC.(4) The computer controls over the system to output arbitrary waveform by MATLAB software, testing and analyzing the output signal in time domain and frequency domain, then sampling data to do LFM pulse compression.