Optimizing the design of piezoelectric polymer ultrasound transducers

The active area of a piezoelectric polymer resonator is an important criterion for transducer operating frequency, bandwidth and insertion loss. Much work has been carried out in selecting the resonator thickness, area, backing and matching layers for optimizing transducer efficiency and bandwidth using piezo-ceramic materials. For these materials, efficiency and bandwidth can be greatly enhanced by electrically tuning the piezo-ceramic element to a pulser-receiver and acoustically matching the element to its front and rear acoustic loads. The piezoelectric polymers, with weak piezoelectric properties, high internal losses, low mechanical quality factor and very low acoustic impedance, yield maximum bandwidth when left untuned. In this work, theoretical derivations are reported for optimizing the active area of the untuned piezoelectric polymer element for maximum power transfer at resonance.