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Radar Digital Waveform Generation Research Based On IF Sampling Technique

Posted on:2004-03-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q SiFull Text:PDF
GTID:1118360095960120Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
With the development of modern digital technology and VLSI, the method of digital waveform synthesis of the pulse compression signals is now widely used in radar systems. The waveform generated using digital systems is of strict coherence, repetitiveness, high stability and programmability, which can also easily realize the waveform parameter agility and generate arbitray waveforms in order to meet the urgent needs for anti-interference and strong viabilities of radars under modern EW environment. Thus, further researches on digital waveform generation are of much importance recently.Based on the error analysis of direct digital synthesis(DDS), this dissertation compares the differences and similarities between direct digital waveform synthesizer(DDWS) and direct digital frequency synthesizer (DDFS). A DDWS system based on IF sampling is presented and realized which can generate multi-wave and multi-mode pulse compression signals, and the theoretical analysis and practical implementation of the system is discussed in details. The technology based on IF sampling is of novel structure, advanced performence, strong felexibility. The narrow band with 1MHz bandwidth and wide band with 3MHz/10MHz bandwidth LFM and NLFM DDWS waveform generator which employed IF sampling technology are implemented. The test results on harmonic, spurious and pulse compression prove that the systems are in the leading level in the related fields at home. This technology is of very important engineering value for the technique reversion of outdated radars and the research and development of modern radars. Meanwhile, this technology cooperating double frequency chain can also generate wide band and ultra-wide band radar pulse compression signals. This dissertation gives a detailed analysis of the various error factors existed in the digital systems and double frequency chain circuits. An experiment waveform generator for a radar sysytem has been implemented, which can generate dual-resolution pulse compressionsignals with 200MHz/66.6MHz bandwidth working at 1200MHz carrier. The test results indicate that the performance of harmonic, spurious and the ripple in passband meet or exceed system requests.The main content and creative work in this dissertation are as follows:(1) On the basis of the introduction of the structure of DDS system, the error model of the DDFS and DDWS system is established and refined. Through the combination of theoretical analysis and computer simulation, the main error factors through the way of DDS, such as the sampling distortion, quantization error, glitch impulse in DAC, mirror images interference and filter amplitude and phase distortion, are discussed. The analysis of impact of sampling distortion and mirror images interference on the pulse compression systems haven't reported on known publications. And the discusson on quantization error and filter amplitude and phase distortion gives some new idea in this paper.(2) A narrow band (1MHz bandwidth) and wide band (3MHz/10MHz bandwidth) radar digital waveform generator based on IF sampling are proposed and implemented. Compared with traditional waveform generator based on orthogonal modulation, the IF sampling methode has great coincidence indicator in amplitude and phase, as well as eminent performance on harmonics and spurious. According to the measurement results, the output harmonics and spurious signals of the generator of the 1MHz bandwidth at 15MHz carrier signals and the generator of 3MHz/10MHz bandwidth at 28~40MHz carrier signals are below -68dB and -60dB respectively, as well as the pulse compressing RMS reach ideal signal performance. The characteristics of both systems is at the forefront of the pulse compression signal generation field in China, and the narrowband system has pass the technical appraisal and has been put into production and applied in a type of radar systems, while the wide band one has been checked and accepted by the research institute and put into use.An experiment DDWS waveform generator system employed 8 bit...
Keywords/Search Tags:Linear Frequency Modulation, Nonlinear Frequency Modulation, Pulse Compression, IF Sampling, Double Frequency Chain
PDF Full Text Request
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