Development and Implementation of a FPGA-based digital beamformer Supervisors: Nandita Bhattacharjee Dr. Andrew Paplinski Dr. Andrew Paplinski Dale Harders

Presentation Outline Presentation Outline –An Ultrasonic Imaging System Overview –Beamforming Fundamentals –Significance of study –Simulator role within this project –Implementation Dale Harders

Ultrasonic Imaging System Overview Dale Harders

Spatial Filter Spatial Filter - Only extract desired directional data - Remaining signals are attenuated Beamforming Fundamentals What is a beamformer? Dale Harders Focussing subsystem Focussing subsystem - Electronic vs. Mechanical - Sharper images are produced

Beamforming Fundamentals Consider how an ultrasonic imaging system operates Dale Harders How is this focussing achieved digitally?

Beamforming Fundamentals Possible Solution: Delay in time Dale Harders Disadvantages: Large storage requirements High clock rates required for fine delays High clock rates required for fine delays

A rotation of complex data in the frequency domain is equivalent to a time delay in the time domain. A rotation of complex data in the frequency domain is equivalent to a time delay in the time domain. Beamforming Fundamentals Better Solution: Phase-shift via complex vector rotation Dale Harders Process data in a different Domain Process data in a different Domain - requires Quadrature sampling (Re, Im) Advantages: Relatively small digital circuitry required Lower sampling rates required Lower sampling rates required

Significance of Study Increase Image Resolution Increase Image Resolution - Improve Signal-to-noise ratio - Improve Signal-to-noise ratio Maintain fast frame-rates Maintain fast frame-rates - Real-time imaging - Real-time imaging Develop 3D-imaging techniques Develop 3D-imaging techniques Ultimate Goals Dale Harders Continuation of Previous Monash Continuation of Previous Monash - (Hampson G, 1998), (Bhattacharjee et al, 2000) - (Prain R, 2001)

Simulator role within this project Ultrasound simulation program Ultrasound simulation program - Developed by Joergen Jensen, Denmark - Running under Matlab Capable of emulating all sub-systems Capable of emulating all sub-systems Field II Dale Harders (Jensen, 1996)

Simulator role within this project Field II Example Origin 0 -x +x+x 0 +z Dale Harders

Simulator role within this project Field II Example Dale Harders

Simulator role within this project Field II Example Origin Dale Harders

Implementation Hardware system Hardware system - Two word-parallel, fully pipelined, CORDIC vector rotators operating in parallel - Summing performed on chip Design implemented on a Xilinx Spartan II FPGA Design implemented on a Xilinx Spartan II FPGA Device Driver Device Driver - Interfaced PCI communications API to Matlab Developed System - Block Schematic Next Slide…

Beamformer System ACCUMULATOR

Conclusion Dale Harders Stable Development Platform built Stable Development Platform built - Easy to use interface for new design test-benching PCI communications PCI communications - Developed a PCI communications interface between Matlab and the Hardware for design verification and future development acceleration Project deliverables satisfied Project deliverables satisfied - Successfully implemented a hardware digital beamformer

References Bhattacharjee N, Paplinski A and Hampson G, "Phase-shift Beamforming", TR 2000/53, CSSE, Monash University, Clayton, 2000 Hampson G.A, "Implementing Multi-Dimensional Digital Hardware Beamformers", PhD thesis, Faculty of Computing and Information Technology. Monash University, Clayton, Jensen J.A, "Field: A program for simulating ultrasound systems", 10th Nordic-Baltic Conference on Biomedical Imaging, vol 4, pg , Prain R, “Parallel CORDIC implementation for hardware beamformers”, Honours Thesis, Department of CSSE, Monash University, Clayton, Dale Harders