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A Research On Ultra Wide Band Radar Pulse Compression Signal Generation Systems

Posted on:2001-06-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y Z LiFull Text:PDF
GTID:1118360002451579Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
Pulse compression is a widespread technology in radar systems used to improve the resolution in range domain. The waveform design theories regarding pulse compression signals with various styles have also been adequately developed. During recent years, with high speed development of multi-targets identification, high resolution microwave imaging and relevant technologies, pulse compression signals with a high time bandwidth product are getting the pressing demands for modem radar researches and applications. Besides designing and selecting waveforms, in order to acquire high time bandwidth product, it is the major practical method to increase the bandwidth of the signal with limited time duration. Wide band or ultra wide band pulse compression signal generation technology is the prerequisite of various imaging radars and target identification algorithms, which makes it possible to detect and identify the buried targets. On the other hand, enlarging signal bandwidth is capable of restraining multi-path effect and clutter echoes, by which the quality of radar echo signals can be improved.Because of the inherent imperfections of analog systems, such as the sensitivity to environment temperature, the nonagile waveforms, the nonideal linearity, repetition and coherence of the waveforms generated, the performance improvement of radar systems with analog pulse compression signal generators is severely restricted. With the modem digital circuits and VLSI developing, the new pulse compression signal generators utilizing direct digital waveform synthesis have been widely researched and applied. Compared to those conventional measures, the system employing digital technology is not sensitive to ambient temperature. The waveform generated by digital systems is with much better repetition and coherency. Especially, the digital generator has a prominent feature that the parameters and waveforms of the output can be easily changed through controlling system clock or selecting a different circuit setup. This is the key point to realize pulse compression waveform agility which can meet the urgent needs for modem radars to reject interference and keep strong survival ability under modem EW environment. Nevertheless, there still exist some difficulties to directly generate pulse compression signals with large absolute bandwidth by digital technology because the speed of current digital devices is limited. The present wide band generators still have to use some analog technologies such us orthogonal modulator, double frequency chain circuits. Thus, further work on wide band generator technology is getting more and more active irj radar research and application field.Based on LFM and NLFM pulse compression signals, this dissertation focuses On the error analysis and the experiment system design of an ultra wide band pulse compression signal generator based on direct digital waveform synthesis (DDWS), orthogonal modulation and double frequency technology. The difference and similarity between DDWS and DDFS waveform synthesizer technology are also compared. Nowadays, with it is supported by government to reform some outdated radar products and develop more advanced radar systems, relevant departments have shown strong interests in the research and application of the wide band or ultra wide band radar pulse compression signal generators adopting digital technology. Because the application in this field just begins in China, especially there are fewer relevant literatures can be found about wide band digital generators. It is impossible to compare and analyze the parameters and specifications of practical systems. Under this background, the analysis and comparison between DDWS and DDFS discussed by this paper provides theoretical bases to choose a reasonable scheme for implementation. Meanwhile, the dissertation also analyzes several key error factors involved in orthogonal modulator and double frequency chain circuits which are essential parts of an ultra-wide band pulse compression signal generator. According to the analysis, "wide...
Keywords/Search Tags:Ultra Wide Band Radar, pulse compression, direct digital waveform synthesis (DDWS), orthogonal modulation, double frequency, linear frequency modulation (LFM), spurious signal reduction, data acquisition.
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