Active Damping of Air-backed Ultrasonic Transducers Using Arbitrary Waveform Generators.

Ultrasound technologies such as high-intensity focused ultrasound and acoustic radiation force imaging require advanced or sophisticated transducer designs. Oftentimes, these designs have transducer requirements of wide power ranges, high sensitivity, and broad bandwidth. However, it would often times be desirable to use the same transducer for both. The objective of this proof-of-concept study is to demonstrate the feasibility of using active damping of air-backed, narrowband transducers to achieve broadband capability. Active damping is accomplished through the use of arbitrary waveform generators to cancel subsequent oscillations beyond the initial excitation. A modified 1-D KLM model written in Matlab is used to guide the design of the waveforms. Optimization of the waveforms is applied to the KLM model using minimization function that minimizes ripple. In the model, - 3 dB transmitted bandwidth increased from 10% to 44% for 1.5-cycle excitation and 11.4% to 63.8% for 1-cycle excitation. Comparable increases in bandwidth were also observed experimentally.