1C-3 A Design for a High-Density Focused Ultrasound Array Addressing and Driving System

Currently, most phased array systems intended for therapy are 1-dimensional and employ between 5 and 200 elements, with a few 2-dimensional systems using several hundred elements. The move towards lambda/2 inter-element spacing, which provides complete 3D beam steering, would require a large number of closely spaced elements (0.15 mm to 3 mm). The solution to the resulting problem of cost and cable assembly size, which this study examines, is to quantize the phases available at the array input. By connecting elements with similar phases to a single wire, a significant reduction in the number of incoming lines can be achieved, while maintaining focusing and beam steering capability. This study has explored the feasibility of such an approach using computer simulations and experiments with a test circuit driving a 100-element linear array. The simulation results demonstrated that adequate focusing can be obtained with only four phase signals, without large increases in the grating lobes or the dimensions of the focus. The experiments showed that the method can be implemented in practice and adequate focusing can be achieved with four phase signals with a reduction of 20% in the peak pressure amplitude squared when compared with the infinite phase resolution case. The results indicate that the use of this technique would make it possible to drive more than 10000 elements with 33 input lines. The implementation of this method could have a large impact on ultrasound therapy and diagnostic devices