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Comparison of Pulse-Compression’s Techniques in Presence of Doppler

HassanNezhad Bibalan, Mohammad Reza | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40570 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Bastani, Mohammad Hassan
  7. Abstract:
  8. - Pulse-compression is one of the spread spectrum techniques that allows a radar to simultaneously achieve the energy of a long pulse and the resolution of a short pulse. The long pulse band-width is increased by phase or frequency modulation, then this modulated long pulse is compressed by matched filter of the receiver. A simple class of pulse-compression waveforms is Binary phase-coded pulse that uses rectangular sub pulses. When the transmitted signal encounters a moving target, the performance of radar degrades due to Doppler frequency shift of received signal. Binary codes have high side lobe levels for long Codes, so to solve this problem the Quadriphase-coded pulse that constructed from prototype Binary code was used. The most popular Technique is linear frequency modulation (LFM) or chirp waveform due to its low side lobe and high peak level. Weighting can be used to decrease the LFM side lobe level. Range-Doppler Coupling characteristic of Frequency modulated waveforms causes an error to estimation of target’s range. As a contribution, a special form of non-linear FM was used to resolve the range Doppler coupling of LFM. There is also another class of pulse-compression waveforms, Frequency-derived polyphase pulse compression waveforms (Frand and P1,P2,P3, P4 codes) that can be derived by sampling the phase of the LFM. To obtain a Doppler tolerant waveform, peak loss and side lobe levels of matched filter output in absence and presence of Doppler are compared for aforementioned waveforms. Performance of output when receiver is a miss-matched filter are also analyzed.

  9. Keywords:
  10. Ambiguity Function ; Matched Filter ; Pulse Compression ; Range-Dappler Coupling ; Doppler Tolerant ; Mismatched Filter

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