An Ultrasound Imaging Front-End System-on-a-Chip with Element-Level Impedance Matching for Acoustic Reflectivity Reduction

This paper presents an ultrasound imaging frontend system-on-a-chip that reduces the acoustic reflectivity of the ultrasound transducer array in a broad bandwidth. It integrates, for the first time, an ultrasound transceiver (HV pulse transmitter and LV analog receiver) and an element-level active capacitive impedance cancellation scheme using an element-level negative impedance converter. The system is designed for low frame rate applications such as intracranial ultrasound (ICUS) and realized in 180-nm HV BCD technology. The ASIC provides highvoltage pulses up to 60 V consuming 3.6 mW and occupying only 2.5 mm
²
. The system-on-a-chip is used with a capacitive micromachined ultrasonic transducer (CMUT) array operating in the 2–4 MHz range and its acoustical reflectivity reduction and imaging capabilities have successfully been demonstrated through pulse-echo measurements and acoustic imaging experiments.