Front-end receiver electronics for high-frequency monolithic CMUT-on-CMOS imaging arrays

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Materials Science

Background:

• High-frequency intravascular ultrasound imaging requires sensitive receiver electronics.
• Monolithic integration of capacitive micromachined ultrasonic transducer (CMUT) arrays with CMOS electronics offers potential for improved performance.
• Current systems face challenges in achieving high receive sensitivity and signal-to-noise ratio (SNR).

Purpose of the Study:

• To design and demonstrate CMOS receiver electronics for monolithic integration with CMUT arrays for intravascular ultrasound imaging.
• To evaluate the advantages of the CMUT-on-CMOS approach for enhanced receive sensitivity and SNR.
• To present a low-noise, high-gain transimpedance amplifier (TIA) design optimized for CMUT elements.

Main Methods:

• Fabrication of a custom 8-inch wafer using a 0.35-microm two-poly, four-metal CMOS process.
• Monolithic integration of CMUT arrays on top of application-specific integrated circuits (ASICs).
• Design and optimization of a transimpedance amplifier (TIA) for CMUT elements, focusing on gain, bandwidth, dynamic range, and power consumption.

Main Results:

• Achieved a 90 fA/√Hz input-referred current noise, below the CMUT element's thermal-mechanical noise.
• Demonstrated successful system operation via pulse-echo measurements.
• Obtained a noise figure of 1.8 dB within the 10 to 20 MHz CMUT bandwidth, confirming transducer-noise-dominated detection.

Conclusions:

• The single-chip CMUT-on-CMOS approach significantly enhances receive sensitivity and SNR for high-frequency ultrasound imaging.
• The optimized TIA design meets the stringent low-noise requirements for CMUT-based systems.
• This integrated technology shows promise for advancing intravascular ultrasound imaging capabilities.