Generating And Processing Technologies Of Wideband Radar Signals

Modern war with high-science and technology requires powerful function and high performance of radar system. The merits of wideband radars with large instantaneous bandwidth signals are high range resolution, anti-jamming, reliability of detection, higher informance measure of recognition and so on, so wideband radar is one of very important and development military projects in the world countries. Especially, generating and processing technology of wideband radar signals with 1GHz instantaneous bandwidth at X band is paid more attention to. Therefore research on generating and processing technologies of wideband radar signal with large instantaneous bandwidth, increasing performance of wideband radar is of much importance recently.Based on error analysis of linear frequency modulation (LFM) signal generation system for wideband radar, some methods of wideband radar signal generation and the modules of system are analyzed in this dissertation, some corresponding error models are made, moreover, generation principle and influence of error in these models are also analyzed in detail. The adjustment methods of some errors from digital-to-analog converter (DAC), analog quadrature modulators and whole system are presented, respectively. At the same time, the signal amplitude error from the Sinc function modulation of DAC is compensated in a real signal generation system. The wideband radar signal generation systems with single-channel based on DDFS and DDWS are developed and designed, moreover, a generation system with two-channel that generates large instantaneous bandwidth radar signals is presented and designed. In addition, an algorithm that is used to measure the linearity of wideband radar signals is presented, and pulse compression methods of wideband radar signals based on intersection of frequency spectrum and dechirp are investigated.The main content and creative work in this dissertation are as follows:1. Two digital waveform generation systems for wideband radar signal with baseband and intermediate frequency sampling structure are designed and developed, that output the LFM signal with 1.3GHz instantaneous bandwidth. The output signal has high linearity, low harmonic and spurious signals. At the present time, the system has been passed the technical appraisal, and the performance of system is foremost in the same domestic systems and arrives at superiority in the same international systems.2. A digital waveform generation system for wideband radar signals based on DDWS and direct IF output structure is designed and developed, that outputs the LFM signal with 20MHz bandwidth at VHF/UHF band. Meanwhile, the signal amplitude error coming from DAC in this system is compensated by a digital predistortion method. The improvement values of signal amplitude are about 1.37dB (20MHz bandwidth) and 2.18dB (40MHz bandwidth), respectively.3. A generation system with two-channel structure that can generate LFM radar signals with large instantaneous bandwidth is presented and designed. The two-channel system has the advantage over the single-channel system. The errors of the system are analyzed. An adaptive digital method of adjustment the error of two-waveform phase is presented. The method of the LFM radar signal synthesis with the two-channel structure hasn't been reported in the current literatures.4. The pulse compression signal generation system based on DDFS structure is investigated, and the error models of system are made. The errors of phase truncation, digit quantified and three errors coming from analog quadrature modulators are analyzed. By means of parallel-path DAC the method that reduces the first spurious signal in DDFS system is analyzed, and an adaptive method of adjustment three errors of analog quadrature modulators is presented. Moreover, algorithms of adjustment the amplitude error and phase error of signal in DDWS system are presented.5. That the linearity of wideband LFM signals exerts an influence on the performance of output signal is analyzed. A digital method of measurement linearity of LFM signals with large instantaneous bandwidth is presented. For the purpose of processing wideband LFM radar signals, the pulse compression methods based on intersection of frequency spectrum and dechirp are investigated, thus the questions that signals with large instantaneous bandwidth can't be sampled, stored and processed are solved.