| 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 thesis, 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 were defined and used. With these new AFE chips, 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 micros 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 at 50 frames/s. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography. One DSP being able to handle both beamforming and back-end processing could lead to low-power and low-cost ultrasound machines, benefiting ultrasound imaging in general, particularly portable ultrasound machines. |
