DESIGN AND OPTIMIZATION OF UNIPOLAR PRESSURE PULSE GENERATORS WITH A SINGLE TRANSDUCER

In this paper a broad bandwidth elastic wave generator is described wh ich can produce unipolar (half-oscillation) longitudinal pressure puls es. Such systems are of great interest in many fields: for instance, i n nondestructive testing when spatial resolution is needed in lossy ma terials. The emitter is composed of a thin piezoelectric transducer co upled with a waveguide and a backing medium. Depending on the impedanc e of each material, both broad proportional and differential bandwidth can be obtained. The theoretical description, which takes into accoun t the connection to an electrical generator, is presented. It allows f or optimization of the performance of the system. These developments a re in good agreement with the experiments which have been carried out. A bandwidth of 185% of the central frequency and pressure pulses of 1 .5-MPa amplitude are obtained. (C) 1998 Acoustical Society of America. [S0001-4966(98)00811-X]