Electrical and Electronics Engineering Department, Bilkent University, Ankara, Turkey.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Apr;57(4):969-76. doi: 10.1109/TUFFC.2010.1501.
The radiation impedance of a capacitive micromachined ultrasonic transducer (cMUT) with a circular membrane is calculated analytically using its velocity profile for the frequencies up to its parallel resonance frequency for both the immersion and the airborne applications. The results are verified by finite element simulations. The work is extended to calculate the radiation impedance of an array of cMUT cells positioned in a hexagonal pattern. A higher radiation resistance improves the bandwidth as well as the efficiency of the cMUT. The radiation resistance is determined to be a strong function of the cell spacing. It is shown that a center-to-center cell spacing of 1.25 wavelengths maximizes the radiation resistance, if the membranes are not too thin. It is also found that excitation of nonsymmetric modes may reduce the radiation resistance in immersion applications.
采用圆形膜片的电容式微机械超声换能器（cMUT）的辐射阻抗在其浸没和空气传播应用的频率范围内通过其速度分布进行了分析计算，直至其并联共振频率。结果通过有限元模拟进行了验证。工作扩展到计算六边形排列的 cMUT 单元阵列的辐射阻抗。较高的辐射电阻可提高 cMUT 的带宽和效率。辐射电阻被确定为单元间距的强函数。如果膜片不太薄，则表明中心到中心的单元间距为 1.25 个波长可使辐射电阻最大化。还发现，在浸没应用中激励非对称模式可能会降低辐射电阻。
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