Enhancing the Performance Characteristics of Piezoelectric Transducers by Broadband Tuning

Effect of broadband tuning in improving the performance characteristics, especially in receive mode, of a piezoelectric transducer working in the sonic frequencies is presented. The broadband tuning technique results in a frequency response function characteristic of a bandpass filter with significant improvements in SNR. When represented by an electrical equivalent circuit, the transducer resembles a half-section bandpass filter. Filter of higher order is obtained by adding external components for enhancing the bandwidth. The circuit parameters are determined from the measured electrical admittance of the transducer in the water. The transducer characteristics with broadband tuning network are simulated and validated experimentally. The impedance phase has improved from -70 degrees to 0 +/- 20 degrees over a broadband leading to an increase in power factor from 0.3 to close to 1. An enhancement of 3 dB in Source Level, 10 dB in Receiving Sensitivity, and 10 dB in Figure of Merit are obtained with 11 kHz increase in bandwidth. An improvement of 7 dB in the noise figure and SNR is also obtained in the receiving mode. The model results are in close agreement with the measured data validating the model. It is found that the broadband tuning network enhances the transducer performance simultaneously in transmitting and receiving modes. This is a significant improvement over conventional shunt tuning and is useful for stand-alone, energy-efficient sonars and two-way acoustic communication systems. The present studies demonstrate that broadband tuning methods in general, originally developed for RF and ultrasonic domains, are applicable in the sonic frequencies also.