Low power delay calculation for digital beamforming in handheld ultrasound systems

In ultrasonic imaging, dynamic receive beamforming is performed with a delay-and-sum operation of the weighted outputs of the transducer elements. The required delay information depends on the position of the transducer elements and the time dependent focus. A new iterative algorithm for calculating this delay information for each channel individually was implemented as a power-optimized VLSI macro employing a tool for physical design oriented custom datapath generation. For a resolution of 1/8 of the sampling period, it comprises only 8 adders and 8 registers per channel and is one key component of a single-chip low power digital beamformer for use in battery operated handheld ultrasound scanners. Operating in a 40 MHz system at 3.3 V, it dissipates 2.1 mW in a 0.5-μm CMOS process