title: Compact FPGA-based beamformer using oversampled 1-bit A/D converters.
abstract: A compact medical ultrasound beamformer architecture that uses oversampled 1-bit analog-to-digital (A/D) converters is presented. Sparse sample processing is used, as the echo signal for the image lines is reconstructed in 512 equidistant focal points along the line through its in-phase and quadrature components. That information is sufficient for presenting a B-mode image and creating a color flow map. The high sampling rate provides the necessary delay resolution for the focusing. The low channel data width (1-bit) makes it possible to construct a compact beamformer logic. The signal reconstruction is done using finite impulse reponse (FIR) filters, applied on selected bit sequences of the delta-sigma modulator output stream. The approach allows for a multichannel beamformer to fit in a single field programmable gate array (FPGA) device. A 32-channel beamformer is estimated to occupy 50% of the available logic resources in a commercially available mid-range FPGA, and to be able to operate at 129 MHz. Simulation of the architecture at 140 MHz provides images with a dynamic range approaching 60 dB for an excitation frequency of 3 MHz.
authors.affiliation: Center for Fast Ultrasound Imaging, Orsted, DTU, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark. bt@oersted.dtu.dk
authors.forename: Borislav Gueorguiev
authors.initials: BG
authors.lastname: Tomov
authors.forename: Jørgen Arendt
authors.initials: JA
authors.lastname: Jensen
mesh_terms: D000703:Analog-Digital Conversion; D004582:Electronics, Medical; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D008838:Microcomputers; D008904:Miniaturization; D019047:Phantoms, Imaging; D018401:Sample Size; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods