High Frequency Piezoelectric Micromachined Transducers with Wide Bandwidth and High Sensitivity

A new model in finite element method to study round-trip performance of piezoelectric micromachined ultrasonic transducers (pMUTs) is established. Most studies on the performance of pMUT are based only on the transmission sensibility, but the reception capacity is as much important as the transmission one, and is quite different from this latter. In this work, the round-trip sensitivity of pMUT is defined as the product of the frequency response of transmitted far field pressure to source voltage excitation and that of reception output to return wave pressure. Based on this sensitivity characteristic, firstly, a multi-parameter optimization for a cavity pMUT is performed using the sensitivity-bandwidth product parameter SBW as criterion. The radii of the electrode and the piezoelectric layer, the thicknesses of the piezoelectric layer and the vibration diaphragm are adjusted to maximize the performance. Secondly, an acoustic matching method is proposed and applied to pMUTs for the first time. As a result, the round-trip sensitivity can be evaluated and the pulse-echo response of wide-band excitation can be simulated, giving the most quantitative and intuitive feedback for pMUT design. The optimization enhances the sensitivity-bandwidth product by 52% when the top electrode and piezoelectric layer are both etched to 75% radius of the cavity beneath; the introduction of an acoustic matching layer shows significant bandwidth expansion in both the transmitting and receiving process.

Section: Modeling and Analyzing Methodsmentioning

confidence: 99%

Sensitivity—Bandwidth Optimization of PMUT with Acoustical Matching Using Finite Element Method

Xü

Wang

et al. 2022

“…The independent resonance peaks overlap into one under load and get a large bandwidth at high frequency [ 11 ]. However, there exist two drawbacks in its further imaging applications: (i) an acoustic lens is needed to focus the beam produced by all the parallel cells [ 12 ], and (ii) the juxtaposition of many elements is hardly compatible with the pitch requirement of a 2D phased array, which limits the steering range. In summary, the existing technology cannot be applied to get a high-frequency broad bandwidth 2D PMUTs phased array.…”

Section: Introductionmentioning

confidence: 99%

Development of Broadband High-Frequency Piezoelectric Micromachined Ultrasonic Transducer Array

Wang

et al. 2021

Piezoelectric micromachined ultrasonic transducers (PMUT) are promising elements to fabricate a two-dimensional (2D) array with a pitch small enough (approximately half wavelength) to form and receive arbitrary acoustic beams for medical imaging. However, PMUT arrays have so far failed to combine the wide, high-frequency bandwidth needed to achieve a high axial resolution. In this paper, a polydimethylsiloxane (PDMS) backing structure is introduced into the PMUTs to improve the device bandwidth while keeping a sub-wavelength (λ) pitch. We implement this backing on a 16 × 8 array with 75 µm pitch (3λ/4) with a 15 MHz working frequency. Adding the backing nearly doubles the bandwidth to 92% (−6 dB) and has little influence on the impulse response sensitivity. By widening the transducer bandwidth, this backing may enable using PMUT ultrasonic arrays for high-resolution 3D imaging.

“…The piezoelectric membrane is the main sensing element that requires attention in every PMUT design. Different membrane shapes have been proposed to investigate the sensitivity and bandwidth characteristics of ultrasonic transducers [ 4 , 8 , 12 ]. Circular- and square-shaped membranes were among the popular shapes chosen for PMUT.…”

Section: Introductionmentioning

confidence: 99%

“…All structural variations impact the performance of a PMUT, either in terms of the receiving sensitivity or frequency bandwidth [ 16 ]. The trade-off between the bandwidth and receiving sensitivity is crucial during the design stage in order for a device to suit a specific application [ 12 , 17 , 18 ]. In this study, a novel structure involving a double flexural membrane with a backing layer is proposed to develop a PMUT that can act as an acoustic receiver in the wide-band, medium-frequency operation range of 300 to 800 kHz.…”

Section: Introductionmentioning

confidence: 99%

A Fluidics-Based Double Flexural Membrane Piezoelectric Micromachined Ultrasonic Transducer (PMUT) for Wide-Bandwidth Underwater Acoustic Applications

Ahmad

Rahman

Zain

et al. 2021

In acoustic receiver design, the receiving sensitivity and bandwidth are two primary parameters that determine the performance of a device. The trade-off between sensitivity and bandwidth makes the design very challenging, meaning it needs to be fine-tuned to suit specific applications. The ability to design a PMUT with high receiving sensitivity and a wide bandwidth is crucial to allow a wide spectrum of transmitted frequencies to be efficiently received. This paper presents a novel structure involving a double flexural membrane with a fluidic backing layer based on an in-plane polarization mode to optimize both the receiving sensitivity and frequency bandwidth for medium-range underwater acoustic applications. In this structure, the membrane material and electrode configuration are optimized to produce good receiving sensitivity. Simultaneously, a fluidic backing layer is introduced into the double flexural membrane to increase the bandwidth. Several piezoelectric membrane materials and various electrode dimensions were simulated using finite element analysis (FEA) techniques to study the receiving performance of the proposed structure. The final structure was then fabricated based on the findings from the simulation work. The pulse–echo experimental method was used to characterize and verify the performance of the proposed device. The proposed structure was found to have an improved bandwidth of 56.6% with a receiving sensitivity of −1.8864 dB rel 1 V µPa. For the proposed device, the resonance frequency and center frequency were 600 and 662.5 kHz, respectively, indicating its suitability for the targeted frequency range.