Software-based ultrasound phase rotation beamforming on multi-core DSP

Phase rotation beamforming (PRBF) is a commonly-used digital receive beamforming technique. However, due to its high computational requirement, it has traditionally been supported by hardwired architectures (e.g., application-specific integrated circuits (ASICs) or more recently field-programmable gate arrays (FPGAs)). In this paper, we investigate the feasibility of supporting software-based PRBF on a multi-core DSP. To alleviate the high computing requirement, the analog front-end (AFE) chips integrating quadrature demodulation in addition to analog-to-digital conversion could be adopted. Under this condition, only delay alignment and phase rotation need to be performed by DSP, substantially reducing the computational load. We implemented the delay alignment and phase rotation modules on a Texas Instruments C6678 DSP with 8 cores. With a sampling rate of 40 MHz and 2∶1 decimation, it takes 200 µs to generate one scanline (2048 samples/scanline) on two cores. With 4 cores, it can support beamforming for 64 channels with 10k scanlines/s, e.g., 200 scanlines/frame and at 50 frames/s. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography.