2019_programme: WAVEFORM DESIGN FOR LOW FREQUENCY SYNTHETIC APERTURE SONAR



  • Session: 04. Towards Automatic Target Recognition. Detection, Classification and Modelling
    Organiser(s): Groen Johannes, Jans Wolfgang, Pailhas Yan, Myers Vincent
  • Lecture: WAVEFORM DESIGN FOR LOW FREQUENCY SYNTHETIC APERTURE SONAR [invited]
    Paper ID: 811
    Author(s): Pailhas Yan
    Presenter: Pailhas Yan
    Presentation type: oral
    Abstract: Wideband sonars effectively utilise their bandwidth to provide high resolution in range. In most of the cases, wideband sonar waveforms are LFM (Linear Frequency Modulated) pulses or linear chirps. For a linear chirp, the\ninstantaneous frequency varies linearly with time. The range resolution signal is obtained through pulse compression or matched filtering. It is well know that\nthe resulting range resolution is inversely proportional to the bandwidth Δf, and that the gain after pulse compression is the product of the bandwidth Δf and the duration of the pulse T. In this talk, we will study the case of Quadratic\nFrequency Modulated (QFM) pulses. We will first derive the matched filtered response of this particular pulse and show that the range resolution and the power gain is similar to the LFM case. We will show however that QFM presents\na non-constant energy distribution in frequency which can be utilised to compensate the transducer energy loss at the lower end of the spectra. QFM can then be used to normalise the overall pulse energy without loss in the SNR\n(Signal to Noise Ratio). We will also demonstrate that in the case of SAS (Synthetic Aperture Sonar) systems and in particular in the case of low frequency SAS, quadratic modulated pulses provide more robustness toward navigation\nerrors and that the resulting PSF (Point Spread Function) is less susceptible to\nblurring effects.
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  • Corresponding author: Dr Pailhas Yan
    Affiliation: CMRE
    Country: Italy
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