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Practical Active Sonar Receiver Systems Using Fast Frequency-Domain Correlation

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[Technical Report, Technical Paper]

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Active sonar systems require good angular and range resolution to localise targets and to combat reverberation 1,2.Range resolution can be achieved using short transmission pulse lengths ie with simple PCW transmissions, range resolution equates to effective transmitted pulse length. However, the peak acoustic power delivered by the transmit array is limited by cavitation, so to achieve the high transmit energies needed for long range detection. long transmit pulses must be used. Consequently, to provide the high energy transmissions for long range together with the good range resolution to combat reverberation, coded transmission waveforms are usually employed. Typical waveform types 2 used in active sonar include linear period PMLPFM chirps which provides a Doppler invariant range-doppler ambiguity function, linear frequency FM chirps with limited Doppler discrimination and pseudo random noise PRN with a thumb-tack range-doppler ambiguity response. Typically these waveforms use time-bandwidth BT products of the order 1000 and the receive processing detection system consists of a collection of matched filters, using Doppler shifted versions of the transmitted waveforms to implement a multi-beam, multi-doppler channel replica correlator system.

Subject Categories:

  • Underwater and Marine Navigation and Guidance
  • Acoustics
  • Theoretical Mathematics

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[A, Approved For Public Release]