Langevin’s contributions to pulse echo piezoelectric transducers

Abstract

Paul Langevin made fundamental discoveries which laid the foundations of modern pulse echo ultrasound over a hundred years ago. He was the first to employ piezoelectric crystals, X-cut quartz, with the propagation and electric axes aligned. In his design, the crystal thickness was a half-wavelength longitudinal wave resonator for both a transmitter and receiver which is the most popular configuration in use today. He invented the Langevin transducer which added two quarter wave layers on either side of the piezoelectric crystal to increase overall efficiency. A mosaic pattern embodied smaller pieces of scarce quartz. His original designs will be demonstrated through simulator models. By selecting ultrasound frequency of 40 KHz, he was able to make more directive beams and extend range for pulse echo detection. By adding triode amplifiers, the sensitivity of reception was increased greatly, and transmission powers of a kilowatt were achieved. With special circuits for making short pulses, long range, high resolution pulse echo ranging became a practical reality. Langevin’s innovations led to sonar and eventually to ultrasound imaging.