Browsing by Subject "Airborne ultrasound"

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Open Access
Design, fabrication and operation of a very high intensity CMUT transmit array for beam steering applications
(2020-12) Khan, Talha Masood
Several studies have reported airborne ultrasound transmission systems focused on achieving beamforming. However, beam steering and beamforming for capacitive micromachined ultrasonic transducers (CMUTs) at high intensity remains to be accomplished. CMUTs, like other ultrasonic transducers, incorporate a loss mechanism to obtain a wide bandwidth. They are restricted to a limited amount of plate swing due to the gap between the radiating plate and the bottom electrode, along with a high dc bias operation. CMUTs can be designed to produce high-intensity ultrasound by employing an unbiased operation. This mode of operation allows the plate to swing the entire gap without collapsing, thus enabling higher intensity. In this study, we use an equivalent circuit-based model to design unbiased CMUT arrays driven at half the mechanical frequency. This model is cross verified using finite element analysis (FEA). CMUT arrays are produced in multiple configurations using a customized microfabrication process that involves anodic wafer bonding, a single lithographic mask, and a shadow mask. We use impedance measurements to characterize the microfabricated devices. We experimentally obtained the highest reported intensity using a microfabricated 2×2 CMUT array driven at resonance in a pulsed configuration. This array is also capable of beam steering and beamforming at a high intensity such that it can steer the entire half-space. The beam obtained from the array is in excellent agreement with the theoretical predictions. The amplitude and phase compensation for the devices remain constant that makes these arrays attractive for applications involving park assist, gesture recognition, and tactile displays.
Open Access
High-Intensity airborne CMUT transmitter array with beam steering
(IEEE, 2020) Khan, Talha Masood; Taşdelen, Akif Sinan; Yılmaz, Mehmet; Atalar, Abdullah; Köymen, Hayrettin
A 2×2 high-intensity CMUT transmit array that is capable of two-dimensional beam steering is presented. The device uses an ac drive voltage at half the ultrasound frequency without any dc bias, enabling the usage of the entire gap height. The device is designed using a large signal equivalent model approach. A fabrication method that requires a single lithographic mask has been used. The fabricated devices are operated at 76 kHz to beam steer at various angles. An equivalent element pressure of 144 dB// 20 μ Pa at the transducer surface was measured. The entire half-space can be steered without any sidelobes and the beam obtained from the array is in excellent agreement with the theoretical predictions. [2020-0253]