The project is oriented to implement a multichannel signal path for ultrasonic air-coupled sonar based on MEMS wideband digital microphones. The proposed solution incorporates the Caravel SoC to manage the output data produced by a custom datapath. The datapath will capture the acoustic signal from an ultrasonic MEMS microphone, demodulate the PDM signal, filter out unwanted spectral components and evaluate signal strength on a base of a configurable threshold. The threshold indicator will control a free-running timer to evaluate the time of flight of an ultrasonic wave, thus range. The proposed solution can be scaled into a multichannel system, reconstructing the acoustic wavefront and thus the angle of arrival of the ultrasonic wave. We will work on the system optimization driven by the resource sharing principle during the design because of the relatively slow intersample interval in a range of a few microseconds. Due to the limited resources of the ChipIgnition shuttle, we propose a threshold-based technique of the acoustic wavefront reconstruction; however, the studies and experience gained during this project will help us to develop more advanced digital beamforming techniques.
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