Abstract
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.
Highlights
There are reports investigating improvements to the bandwidth performance of air-coupled ultrasonic transducers, including applying biased voltage to piezoelectric micromachined ultrasonic transducers (PMUTs), utilizing multifrequency piezoelectric arrays, exploiting the non-resonant vibration of electromechanical films, and utilizing capacitive ultrasonic transducers and capacitive micromachined ultrasonic transducers (CMUTs).10–14 challenges persist due to the necessary compromise between bandwidth, frequencyresponse, sensitivity, directivity, cost, complexity, robustness, operation temperature, and intrinsic safety of the transducers
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
An edge-clamped non-magnetic conductive foil, whose lateral dimensions are significantly greater than its thickness, is placed in an in-plane radial static magnetic field Bs,in in the vicinity of a solenoid carrying an alternating current Jc
Summary
There are reports investigating improvements to the bandwidth performance of air-coupled ultrasonic transducers, including applying biased voltage to PMUTs, utilizing multifrequency piezoelectric arrays, exploiting the non-resonant vibration of electromechanical films, and utilizing capacitive ultrasonic transducers and capacitive micromachined ultrasonic transducers (CMUTs).10–14 challenges persist due to the necessary compromise between bandwidth, frequencyresponse, sensitivity, directivity, cost, complexity, robustness, operation temperature, and intrinsic safety of the transducers. The WEMDAT has been shown to operate effectively as a wideband ultrasonic receiver through the measurement in a pitch-catch configuration.
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