Abstract
Piezoelectric micromachined ultrasonic transducers (PMUTs) are used to receive and transmit ultrasonic signals in industrial and biomedical applications. This type of transducer can be miniaturized and integrated with electronic systems since each element is small and the power requirements are low. The bandwidth of the PMUT may be narrow in some conventional designs; however, it is possible to apply modified structures to enhance this. This paper presents a methodology for improving the bandwidth of air-coupled PMUTs without sensitivity loss by connecting a number of resonating pipes of various lengths to a cavity. A prototype piezoelectric diaphragm ultrasonic transducer is presented to prove the theory. This novel device was fabricated by additive manufacturing (3-D printing), and consists of a polyvinylidene fluoride thin film over a stereolithography designed backplate. The backplate design is inspired by a pipe organ musical instrument, where the resonant frequency (pitch) of each pipe is mainly determined by its length. The -6-dB bandwidth of the "pipe organ" air-coupled transducer is 55.7% and 58.5% in transmitting and receiving modes, respectively, which is ~5 times wider than a custom-built standard device.
Highlights
H IGHER resolution is the one of the most important requirements in nondestructive evaluation (NDE), biomedical imaging, and underwater sonar [1]
The pipe organ backplate proposed in this paper is a novel design that can improve the bandwidth of air-coupled Piezoelectric micromachined ultrasonic transducers (PMUTs) without sensitivity loss or increase of active area
A PMUT utilizes a piezoelectric layer on the top of a silicon membrane and operates in a flexural mode
Summary
H IGHER resolution is the one of the most important requirements in nondestructive evaluation (NDE), biomedical imaging, and underwater sonar [1]. Layers or damping materials to broaden the frequency response around resonances [2] Whereas the piezoelectric transducers use thickness mode resonances, the micromachined ultrasonic transducers (MUTs) have a thin flexible film to transmit and receive ultrasound. MUTs have better performance in air because the flexible film is easier to couple with the media, with a more closely matched mechanical impedance. The MUTs’ family includes piezoelectric MUTs (PMUTs) and capacitive MUTs (CMUTs) The pipe organ backplate proposed in this paper is a novel design that can improve the bandwidth of air-coupled PMUTs without sensitivity loss or increase of active area.
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