UACE2017 Proceedings: Doppler estimates for large time-bandwidth products using linear frequency modulated active sonar pulses

• Session:
  Large Time-Bandwidth acoustic signals for target detection and tracking
• Paper:
  Doppler estimates for large time-bandwidth products using linear frequency modulated active sonar pulses
• Author(s):
  Jeffrey R. Bates, Paul C. Hines, Gaetano Canepa, Alessandra Tesei, Gabriele Ferri, Kevin D. Lepage
• Abstract:
  Doppler sensitive active sonar waveforms have the potential to distinguish/classify target echo returns from stationary compact clutter and to improve target tracking by providing the tracker with an estimate of the Doppler range rate. Linearly frequency modulated (LFM) active sonar waveforms are typically assumed to be Doppler insensitive. However, for LFM pulses with a high Time-BandWidth Product (TBWP), this assumption is no longer valid and Doppler sensitivity can be exploited. On the other hand, when the acoustic channel coherence is low, increasing the TBWP can result in lower than theoretically expected matched filter gain and is a potential drawback.\nA sea trial was carried out by the Littoral Continuous Active Sonar (LCAS) Multi-National Joint Research Project (MN-JRP) in the gulf of Taranto in October of 2016. Two LFM active sonar waveforms were simultaneously transmitted to detect a simulated target (echo repeater). The first LFM waveform was 1 second in duration between 2700 and 3500 Hz (low TBWP Pulse Active Sonar - PAS). The second LFM waveform was 20 seconds in duration between 1800 and 2600 Hz (high TBWP Continuous Active Sonar - CAS). Each waveform had a repetition interval of 20 seconds and had equal total energy per pulse.\nTrial results from the high TBWP CAS waveform demonstrate that some of the echo level can be recovered using Doppler processing and an estimate of the Doppler range rate can be provided to a tracker and used in echo classification. However, the signal-to-reverberation ratio of the CAS waveform was significantly lower than that of the low TBWP PAS waveform. These results demonstrate the feasibility of estimating target range rate with high TBWP LFM pulses (CAS) - a promising technique for scenarios with sufficient acoustic channel coherence.\nThis work was made possible by the LCAS MN-JRP.
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Contact details

• Contact person:
  Dr Jeffrey Bates
• e-mail:
  
• Affiliation:
  NATO Science and Technology Organization - Centre for Maritime Research and Experimentation
• Country:
  Italy