An ultrasonic pulser/receiver system with extended dynamic range and low distortion

The increasing sophistication of quantitative ultrasonic techniques and signal processing requires signal electronics systems having performance characteristics which are significantly better than those of conventional designs. Better performance, in terms of extended signal dynamic range, stability, bandwidth, and signal distortion, is becoming essential for many applications in the laboratory and in the field; further, software control of large automated systems often requires specialized circuit configurations, which are not available. This paper addresses the design of an ultrasonic signal system which has proven very useful as the major signal-conditioning component in obtaining improved performance in large, automated ultrasonic systems. Extended dynamic range comes from improvements in the signal/noise ratio (SNR). Both terms in the ratio are addressed, increased sensitivity through pulser design, and noise primarily in receiver design and careful attention to circuit details. The system is entirely modular and includes provisions for software-driven gain control and random multiplexing of many channels. The key, and most difficult, elements in the system are the pulser and amplifier. The major part of the discussion will be on these elements and the rationale for their design, rather than on circuit details. Use of these elements in large automated systems and in laboratory investigations will also be discussed.