Smith Matching for CMUTs-based Biochemical Resonant Sensor

A LC smith matching method for capacitive micromachined ultrasonic transducers (CMUTs) was presented for biochemical application. We completed the fabrication of CMUTs based on the direct bonding technology. A modified Butterworth van-Dyke (BvD) model with lumped elements for functionalized CMUTs were proposed to fit the electrical impedance and phase of CMUTs, which were accurately measured by the impedance analyzer. The series and parallel frequencies of CMUTs were obtained. It is difficult for the functionalized CMUTs to achieve the transmission from capacitive reactance to inductive reactance at relatively low DC voltage. And the proposed LC matching network can optimize the properties of impedance, phase, resistance, especially reactance near the resonant region. This is important for the real-time oscillator design, which needs strict condition for the Barkhausen stability criterion of gain and phase.