Air-coupled ultrasonic applications of ferroelectrets

Improvement of ferroelectret transducers for air-coupled ultrasonic applications was demonstrated on the base of optimization of the ferroelectret electromechanical properties and adjustment of the ferroelectret transducers to the ultrasonic system. Controlled inflation of the polypropylene ferroelectret films results in an increase of the coupling factor in two and the figure of merit in ten times. Integration of a pre-amplifier with high impedance matching increases the ferroelectret transducer sensitivity in 40 dB. Ferroelectret transducers are characterized by the broad transmission band with smooth amplitude-frequency dependence and provide a well shaped and short pulse transmitted through the air.