低噪声电容式超声传感器的结构与电路设计

本文提出了一种紧凑的可动浮栅型电容式超声传感器(Capacitive Micromachined Ultrasonic Transducer,CMUT)器件结构和低噪声高频电路。该结构包含通常CMUT上下电极和MOS晶体管。建模对浮栅型CMUT器件进行了直流分析和时变电容的瞬态分析,模拟结果表明该传感器结构比传统CMUT具有更低的寄生电容和输出阻抗。在1.5Pa超声声压下进行Cadence和ANSYS仿真,输出信号为40.1mV,在1MHz等效输出噪声为16.59nV/Hz1/2,直流增益为74.73dB,单位增益带宽为488MHz。指标优于传统的CMUT结构,具有医学三维成像的应用前景。

The Design of Low Noise Circuit and Structure for CMUT Sensor

A compact CMUT structure with movable floating gate and low noise broad bandwidth circuit is presented in this paper. The new active CMUT structure comprises two traditional CMUT electrodes and MOS transistor beneath it. Its spice model on DC analysis and transient analysis with time-varying capacitor is investigated. It exhibits low overall parasitic capacitance and low output impedance compared with traditional one. According to Cadence simulation results under 1.5Pa ultrasound pressure, the output signal amplitude is 40.1 mV, while the noise floor is 16.59 nV/Hz1/2 at 1MHz operation frequency of CMUT receiver, unit gain frequency is 488 MHz and DC gain is 74.73 dB. These results show that the proposed CMUT structure is superior to existing one and has advantages to make an interesting potential application on CMUT array imaging.