Correlation-based in-air sonar sensor arrays for 3D object tracking and identification

The developed airborne ultrasonic ranging systems employ digital-signal-processing techniques in the attempt to perform digital time-of-flight measurements using correlation methods. The main emphasis in this paper is given to the description of the technical solutions we have adopted in an effort to drive the system complexity down. Bandwidth sampling and digital interpolation techniques are proposed to perform the coherent demodulation of the narrowband received signals to baseband, so as to reduce the overall time complexity involved in computing the correlation functions. Via standard analog multiplexing techniques a sampling frame is defined to manage a number of transducers through a single, relatively slow analog-to-digital converter. Two versions of tracking sonar devices endowed with one transmitting transducer and four receiving transducers for operation at either high or low ultrasonic frequencies are illustrated.