Wideband electromagnetic dynamic acoustic transducers (WEMDATs) for air-coupled ultrasonic applications

Achieving sufficient energy transmission over a wide frequency range is a challenge which has restricted the application of many types of air-coupled ultrasonic transducers. Conventional transducer configurations such as the piezoelectric micromachined or flexural ultrasonic transducers can be considered as narrowband. This study reports a type of ultrasonic transducer, the wideband electromagnetic dynamic acoustic transducer (WEMDAT), which operates through a combination of electromagnetic induction and Lorentz force with dynamic behaviour of a micro-scale-thick conductive film. WEMDAT prototypes have been designed, fabricated, and tested, showing their compatibility with both low and high power inputs, operating efficiently as a wideband transmitter from 46.4 kHz to 144.6 kHz with a good directivity. The WEMDAT has also been shown to operate effectively as a wideband ultrasonic receiver through the measurement in a pitch-catch configuration. The WEMDAT prototypes possess an adjustable drive coil lift-off distance from the active membrane, providing flexibility for optimizing the sensitivity of the transducers for different input levels. The performance of the WEMDATs can be optimized, showing significant potential for air-coupled ultrasonic applications.