Front-end IC design for intravascular ultrasound imaging

Capacitive micromachined ultrasonic transducers (cMUT) technology is a new trend for intravascular ultrasound (IVUS) imaging. Large bandwidth, high sensitivity and compatibility to CMOS processes makes the cMUT a better choice compared to the conventional piezoelectric transducer. To exploit the merits of cMUT technology, an accurately designed front end circuit is required. The circuit functions as an output pulse driver for the generation of the acoustic signal and buffers the return echo. For an accurate evaluation before tape-out, the circuit has to be simulated using the post-layout extracted netlist of the IC with the electrical equivalent circuit that models the transducer pulse-echo behavior. In this paper, we present two different designs of front-end IC for 2D cMUT arrays that can be used for intravascular ultrasound imaging system. To simulate the response of the front-end circuit, we first developed a pulse-echo model for an array element using Mason Equivalent Circuit. The model is then combined with the front-end circuit using Cadence Spectre. The simulation results are verified by comparing them to experimental data obtained from the manufactured front-end IC. The results show that the front-end circuit tested with the equivalent circuit model of the cMUT elements is promising for the optimization of the overall system performance before manufacturing.