Dual-electrode CMUT optimization for CMUTs with uniform and non-uniform membranes

In this paper, we report optimization results on dual-electrode CMUTs with uniform and non-uniform membranes. The electromechanical coupling coefficient (k²) is both simulated and experimentally measured for conventional and dual-electrode CMUTs. The electromechanical coupling coefficient (k²) of 0.82 at 90% of collapse voltage as well as 136% 3dB one-way fractional bandwidth is measured with dual-electrode CMUT with non-uniform membranes. The dual-electrode structure provides high coupling coefficient in a large DC bias range without collapsing the membrane while the large bandwidth is achieved by utilizing a non-uniform membrane. In addition, approximately 20 dB increase in transduction performance is illustrated with dual electrode CMUT with non-uniform membrane as compared to conventional CMUT with uniform membrane.