Pulse compression techniques applied to a very shallow water data

An analysis of pulse compression techniques to improve range resolution of acoustic reflection data in very shallow waters is presented. A linear array with 20 hydrophones spread over 40 meters is towed behind a resonant acoustic source. This system is used to investigate regions with water column ranging from 4 m to 10 m depth. In order to obtain increased range resolution while maintaining an appropriated signal-to-noise ratio, swept sine signals (chirp) were used to ensonify the environment. In this case, long duration pulses are emitted by the source and then compressed during the data processing stage. This process allows easy location of the reflections in the signal. For the analysis, different types of chirp pulses were created and its propagation through the subsurface was simulated. The resulting signals are processed using known compression techniques like the matched filtering and the deconvolution. The objective of the study is to select a combination of excitation signal and processing technique that gives best range resolution and signal-to-noise ratio. Results are discussed and the benefit of each type of signal and processing technique are presented.