2023_programme: Performance of the Shoelace Waveform for High Duty Cycle Multistatic Sonar

• Session: 02. Advances in acoustic measurement systems: Technologies and applications
  Organiser(s): Alessandra Tesei and Purnima Ratilal-Makris
• Lecture: Performance of the Shoelace Waveform for High Duty Cycle Multistatic Sonar [invited]
  Paper ID: 1866
  Author(s): Grimmett Doug
  Presenter: Grimmett Doug
  Abstract: High duty cycle (HDC) sonar operations that use continuous (or near continuous) acoustic transmissions offers potential improvements over pulsed active sonar by providing an order-of-magnitude or more increase in the number of detection opportunities. This can come at the cost of a reduction in received signal excess levels, but can still provide better performance at the output of a tracker, with improved target holding and localization. A typical HDC signal is a long-duration LFM waveform, which is then divided into small frequency sub-bandwidths for processing. \nIn multistatic sonar, multiple acoustic receivers and transmitters operate together as a network. With multiple sources transmitting continuously, mutual interference is likely and this must be mitigated. Using identical waveforms for multiple sources will yield ambiguity about detection contact localization. Using different waveforms will not suffer the ambiguity, but may cause mutual interference. Some advanced waveforms are proposed, which are designed to be mutually orthogonal, requiring increased processing load/complexity and with other constraints. \nThis paper describes a simple waveform, the “Shoelace” waveform, which is transmitted with both up-swept LFM and down-swept LFM waveforms simultaneously. This approach minimizes, but does not eliminate the mutual interference of the two signals on each other, but can still provide an overall increase in multistatic performance. The processing method for the HDC Shoelace waveform is described and the costs and benefits of its use are detailed. The Shoelace waveform was transmitted during the NATO LCAS’15 sea trial, a shallow-water HDC sonar experiment. The processing method has been applied to the LCAS’15 data, and an analysis of the results are provided. The detection and tracking performance of this waveform are presented, showing it to be a viable candidate for multistatic HDC operations.
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• Corresponding author: Mr Doug Grimmett
  Affiliation: Naval Information Warfare Center (NIWC) Pacific
  Country: United States
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