Design and optimization of unipolar pressure pulse generators with a single transducer

In this paper a broad bandwidth elastic wave generator is described which can produce unipolar (half-oscillation) longitudinal pressure pulses. Such systems are of great interest in many fields: for instance, in nondestructive testing when spatial resolution is needed in lossy materials. The emitter is composed of a thin piezoelectric transducer coupled with a waveguide and a backing medium. Depending on the impedance of each material, both broad proportional and differential bandwidth can be obtained. The theoretical description, which takes into account the connection to an electrical generator, is presented. It allows for optimization of the performance of the system. These developments are 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.