Measurement uncertainty analysis of field-programmable gate-array-based, real-time signal processing for ultrasound flow imaging

<p>Research in magnetohydrodynamics (MHD) aims to understand the complex interactions of electrically conductive fluids and magnetic fields. A promising approach for investigating complex instationary flow phenomena are lab-scale experiments with low-melting alloys. They require a noninvasive flow instrumentation for opaque liquids with a high spatiotemporal resolution, a low velocity uncertainty and a long measurement duration. Ultrasound Doppler velocimetry can achieve multiplane, multicomponential flow imaging with multiple linear ultrasound arrays. However the average raw data output amounts to <span class="inline-formula">1.2 GBs⁻¹</span> at a frame rate of <span class="inline-formula">33 Hz</span> in a typical configuration for 200 transducers. This usually prevents long-duration measurements when offline signal processing is used.</p> <p>In this paper, we propose an online signal-processing chain for pulsed-wave Doppler velocimetry that is tailored to the specific requirements of flow imaging for lab-scale experiments. The trade-off between measurement uncertainty and computational complexity is evaluated for different algorithmic variants in relation to the Cramér–Rao bound. By utilizing selected approximations and parameter choices, a prepossessing could be efficiently implemented on a field-programmable gate array (FPGA), enabling a typical reduction of the data bandwidth of <span class="inline-formula">6.5:1</span> and online flow visualization. We validated the performance of the signal processing on a test rig, yielding a velocity standard deviation that is a factor of <span class="inline-formula">3</span> above the theoretical limit despite a low computational complexity.</p> <p>Potential applications for this signal processing include multihour flow measurements during a crystal-growth process and closed-loop velocity feedback for model experiments.</p>

Abstract licence: CC BY

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