Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA.
Ultrasonics. 2014 Jan;54(1):99-105. doi: 10.1016/j.ultras.2013.03.016. Epub 2013 Apr 22.
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 study, we investigated 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. We found it takes 200 μs to beamform 2048 samples from 64 channels using 2 cores. With 4 cores, 20 million samples can be beamformed in one second. Therefore, ADC frequencies up to 40 MHz with 2:1 decimation in AFE chips or up to 20 MHz with no decimation can be supported as long as the ADC-to-DSP I/O requirement can be met. 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.
相控阵波束形成（PRBF）是一种常用的数字接收波束形成技术。然而，由于其计算要求较高，传统上一直由硬件架构支持，例如专用集成电路（ASIC）或最近的现场可编程门阵列（FPGA）。在本研究中，我们研究了在多核 DSP 上支持基于软件的 PRBF 的可行性。为了缓解计算要求高的问题，定义并使用了集成正交解调以及模数转换的模拟前端（AFE）芯片。有了这些新的 AFE 芯片，仅需由 DSP 执行延迟对齐和相位旋转，从而大大降低了计算负载。我们在具有 8 个内核的德州仪器 C6678 DSP 上实现了延迟对齐和相位旋转模块。我们发现，使用 2 个内核对来自 64 个通道的 2048 个样本进行波束形成需要 200μs。使用 4 个内核，每秒可以对 2000 万个样本进行波束形成。因此，只要满足 ADC 到 DSP 的 I/O 要求，就可以支持 AFE 芯片中 ADC 频率高达 40 MHz 且 2:1 抽取或 ADC 频率高达 20 MHz 且无抽取。其余 4 个内核可以用于后端处理任务和应用程序，例如彩色多普勒或超声弹性成像。一个 DSP 能够同时处理波束形成和后端处理，可实现低功耗、低成本的超声机，从而普遍受益于超声成像，特别是便携式超声机。
