Capacitive Micromachined Ultrasonic Transducer with a Force Plate (CMUT-FP)

We introduce a new CMUT structure (CMUT-FP) to increase the acoustic output pressure. The new structure contains a second plate (force plate) underneath the CMUT plate. The second plate is connected to the CMUT plate at its center with a short shaft, acting as the top electrode of the CMUT. The force plate/CMUT plate combination has two coupled resonators and acts like a resonant mechanical transformer enabling more electrical power delivery into the cell and increasing the output pressure. In the transmit mode, it transforms the higher velocity of the force plate to a higher force in the CMUT plate at the resonant frequency. The acoustic pressure performance of CMUT-FP under different operating states is investigated using finite-element-simulations as a function of frequency and compared with the performance of conventional CMUT operating in uncollapsed and collapsed states. The simulations show that several times higher pressure is possible at the expense of reduced bandwidth.