Georgia Institute of Technology, School of Electrical and Computing Engineering, Atlanta, GA, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Aug;58(8):1658-68. doi: 10.1109/TUFFC.2011.1993.
This paper describes the design of CMOS receiver electronics for monolithic integration with capacitive micromachined ultrasonic transducer (CMUT) arrays for highfrequency intravascular ultrasound imaging. A custom 8-inch (20-cm) wafer is fabricated in a 0.35-μm two-poly, four-metal CMOS process and then CMUT arrays are built on top of the application specific integrated circuits (ASICs) on the wafer. We discuss advantages of the single-chip CMUT-on-CMOS approach in terms of receive sensitivity and SNR. Low-noise and high-gain design of a transimpedance amplifier (TIA) optimized for a forward-looking volumetric-imaging CMUT array element is discussed as a challenging design example. Amplifier gain, bandwidth, dynamic range, and power consumption trade-offs are discussed in detail. With minimized parasitics provided by the CMUT-on-CMOS approach, the optimized TIA design achieves a 90 fA/√Hz input-referred current noise, which is less than the thermal-mechanical noise of the CMUT element. We show successful system operation with a pulseecho measurement. Transducer-noise-dominated detection in immersion is also demonstrated through output noise spectrum measurement of the integrated system at different CMUT bias voltages. A noise figure of 1.8 dB is obtained in the designed CMUT bandwidth of 10 to 20 MHz.
本文描述了用于与电容式微机械超声换能器 (CMUT) 阵列单片集成的 CMOS 接收器电子设备的设计，用于高频血管内超声成像。在 0.35-μm 两层四金属 CMOS 工艺中制造了一个定制的 8 英寸（20 厘米）晶圆，然后在晶圆上的专用集成电路 (ASIC) 上构建 CMUT 阵列。我们讨论了单芯片 CMUT-on-CMOS 方法在接收灵敏度和 SNR 方面的优势。作为具有挑战性的设计示例，讨论了针对前向容积成像 CMUT 阵列元件的跨阻放大器 (TIA) 的低噪声和高增益设计。详细讨论了放大器增益、带宽、动态范围和功耗之间的权衡。通过 CMUT-on-CMOS 方法提供的最小寄生效应，优化的 TIA 设计实现了 90 fA/√Hz 的输入参考电流噪声，小于 CMUT 元件的热机械噪声。我们通过脉冲回波测量展示了成功的系统运行。通过在不同的 CMUT 偏置电压下测量集成系统的输出噪声谱，还证明了在浸没状态下以换能器噪声为主的检测。在设计的 CMUT 带宽为 10 至 20 MHz 时，获得了 1.8 dB 的噪声系数。
