Airborne capacitive micromachined ultrasonic transducers (CMUTs) have predominantly large input capacitive reactance with small series radiation resistance. To maximize the acoustic power radiation at resonance we employ low cost LC matching networks between the low output impedance driving source and CMUT transducer. Conventional LC networks, including pi and T-network topologies are employed to provide a high-Q match. An important free parameter that controls the bandwidth of match in pi and T-networks is the center impedance. Since a simple pi-network can be formed from two basic L-sections, the center impedance of two L-sections provides control over the bandwidth of match. Hence these are tunable-Q matching networks. We use the lumped circuit model of CMUT to derive the input impedance of CMUT at resonance. At resonance the lumped equivalent circuit of transducer can be reduced to a series RC circuit consisting of radiation resistance and transducer’s equivalent capacitance only. From the input impedance of CMUT we determine the lumped inductance and capacitances of various LC matching networks. The aim of these matching networks is to cancel the large input capacitive reactance of CMUT cell and to match the cell’s radiation resistance to source resistance at resonance. We report significant improvement in the radiated power when CMUT is driven at resonance using the proposed matching schemes.

机载电容微加工超声换能器（CMUT）主要具有较大的输入电容电抗，而串联辐射电阻较小。为了使共振时的声功率辐射最大化，我们在低输出阻抗驱动源和CMUT换能器之间采用了低成本的LC匹配网络。包括pi和T网络拓扑在内的常规LC网络用于提供高Q匹配。控制pi和T网络中匹配带宽的重要自由参数是中心阻抗。由于可以由两个基本的L构成一个简单的pi网络截面，两个L截面的中心阻抗可控制匹配带宽。因此，这些是可调Q匹配网络。我们使用CMUT的集总电路模型来推导谐振时CMUT的输入阻抗。在谐振时，换能器的集总等效电路可以简化为仅由辐射电阻和换能器的等效电容组成的串联RC电路。根据CMUT的输入阻抗，我们可以确定各种LC的集总电感和电容匹配网络。这些匹配网络的目的是消除CMUT单元的大输入电容电抗，并使单元的辐射电阻与谐振时的源电阻相匹配。我们报告了使用建议的匹配方案在共振条件下驱动CMUT时辐射功率的显着改善。