Digital Phase Modulation and Correlation Processing of Ultrasound Signals for Pulsed Measurements in an Inhomogeneous Medium

Abstract

A method and hardware for ultrasonic control of an inhomogeneous gaseous medium are presented. An algorithm based on digital phase modulation of pulse signals and their correlation processing is used to increase the resolution of an ultrasonic device. The algorithm allows high-resolution measurements of the time delay between the ultrasound pulses that arrive at a receiver along different propagation paths in an inhomogeneous medium. It is shown that it is possible to measure small values of time delays by analyzing the asymmetry of the cross correlation functions of signals. Laboratory experimental measurements carried out under scattering of ultrasound in an inhomogeneous airflow are described. The possibility of measuring relative time delays of 3–5 μs of pulses at the 40-kHz carrier frequency of ultrasound is shown.