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空气耦合的宽频带CMUT微元及阵列设计

Design of Air-Coupled Broadband CMUT Micro-Elements and Array Configurations

  • 摘要: 针对中频段(200 kHz~2 MHz)空气耦合电容式MEMS超声换能器带宽窄、灵敏度低的问题,本文采用微元结构设计和阵列布局优化的方法实现了具备高灵敏度和宽频带的电容式MEMS超声换能器微元及阵列。微元通过圆环形电极与镍凸环的复合结构调节振膜刚度,使振膜呈现活塞运动模式,从而提升灵敏度;阵列采用异构−同构协同的新型面阵布局,通过横向异构设计(不同微元频带交叠)拓宽带宽,并利用纵向同构设计(相同微元输出叠加)增强整体灵敏度,实现灵敏度和带宽的协同优化。基于COMSOL软件对几何结构进行参数优化和性能仿真,结果表明,设计的电容式MEMS超声换能器微元在1.00 MHz的中心频率下能达到21.00 µV·Pa−1/mm2的接收灵敏度和1.05 kPa·V−1/mm2的发射灵敏度。阵列设计在中频段内实现了111.75%的−6 dB分数带宽和230.15 nA的峰值输出电流。最后,基于MEMS加工工艺设计了电容式MEMS超声换能器的制备工艺,为实际制造提供了具体实验方案。

     

    Abstract: To address the issues of narrow bandwidth and low sensitivity in air-coupled CMUT operating in the mid-frequency range (200 kHz−2 MHz), this study proposes a high-sensitivity broadband CMUT element and array through element structure design and array configuration optimization. The element employs a composite structure combining annular electrodes with nickel convex rings to regulate diaphragm stiffness, enabling piston-mode vibration for enhanced sensitivity. The array adopts a novel hybrid heterogeneous-homogeneous planar configuration: lateral heterogeneous design (frequency band overlap of different elements) expands bandwidth, while longitudinal homogeneous design (output superposition of identical elements) boosts overall sensitivity, achieving synergistic optimization of both parameters. Parametric optimization and performance simulation using COMSOL software demonstrate that the proposed CMUT element achieves a receiving sensitivity of 21.00 µV·Pa−1/mm2 and a transmitting sensitivity of 1.05 kPa·V−1/mm2 at the central frequency of 1.00 MHz. The array design realizes 111.75% −6 dB fractional bandwidth and 230.15 nA peak output current within the mid-frequency range. Finally, a CMUT fabrication process based on MEMS manufacturing technology has been established, delivering concrete experimental protocols for practical implementation.

     

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