DESIGN AND EVALUATION OF A FEEDBACK BASED PHASED-ARRAY SYSTEM FOR ULTRASOUND SURGERY

A driving system has been designed for phased array ultrasound applica tors. The system is designed to operate in the bandwidth 1.2 to 1.8 MH z with independent channel power control up to 60 W (8 bit resolution) for each array element. To reduce power variation between elements, t he system utilizes switching regulators in a feedback loop to automati cally adjust the DC supply of a class D/E power converter. This feedba ck reduces the RF electrical power variation from 20% to 1% into a IS element array. DC-to-RF efficiencies close to 70% for all power levels eliminates the need for large heat sinks. In addition to power contro l, each channel may be phase shifted 360 degrees with a minimum of 8 b it resolution. To ensure proper operation while driving ultrasound arr ays with varying element sizes, each RF driving channel implements pha se feedback such that proper phase of the driving signal is produced e ither at the amplifier output before the matching circuitry or after t he matching circuitry at the transducer face. This feedback has been e xperimentally shown to increase the focal intensities by 20 to 25% of two tested phased arrays without array calibration using a hydrophone.