Determining the pulse-echo electromechanical characteristic of a transducer using flat plates and point targets

Abstract

A common technique to determine the electromechanical response of a spherically focusing transducer is to use a reference pulse echo from a flat plate in the focal plane of the transducer. We show that when the pressure focusing gain of the transducer is much greater than unity, the focal plane reflection is a valid approximation of the desired electromechanical response. An alternative calibration target is a point scatterer and we show theoretically and experimentally that this waveform is the double time differential of the flat-plate response. The use of calibration to describe general scatterers through a Born approximation (Jensen, J. A. (1991), J. Acoust. Soc. Am. 89, 182–190) is discussed.