A model for low noise design of ultrasonic transducers

Abstract

Several practical ultrasonic applications are limited by available signal to noise ratio (SNR). In many cases, the limiting factor on SNR is determined by intrinsic self noise, arising from the transducer and preamplifier system. This work describes the development and evaluation of a mathematical model to facilitate a design process for maximum SNR. This model includes the major noise sources as a function of transducer type, construction and operating environment. Centred around the linear systems approach, the model is wideband and valid for any thickness mode transducer system. Simulated and experimental results are performed in both air and water for different transducer configurations, including piezopolymer and piezocomposite devices. The separate contributions arising from transducer noise, preamplifier noise and ambient noise are identified, with good agreement between theoretical and experimental data. Some fundamental design guidelines for effective low noise design are also presented.