Synchronization Technique for Doppler Signal Extraction in Ultrasonic Vibration Measurement Systems

Doppler signal extraction through a synchronization technique is proposed for ultrasonic vibration measurement systems, which employ a pair of transducers and a vibrating object. Due to Doppler effect, the received ultrasonic signal is phase modulated. The moving window filter (MWF) tuned for the center frequency of the carrier converts phase-modulated signal into amplitude-modulated signal because of the carrier frequency variation. To retrieve the vibrating object information, the proposed technique based on MWF synchronizes its output with the phase-modulated received signal so that it can accurately track the carrier variation. The synchronization is achieved through adaptive sampling frequency adjustment. With ultrasonic carrier tracking, the Doppler signal is retrieved that carries the vibration amplitude and frequency information. The simulation results are validated through experimental investigation carried out for wide variation of the carrier by digital implementation.