Design of a digital phase shift beamformer for ultrasonic imaging

We present a digital phase shift beamformer system for medical ultrasound imaging applications. By starting with an overview of the system structure, we focus our discussion on the digital circuit implementation of the complex envelope signal phase shifting by employing the CORDIC algorithm. We analyze the phase delay error tolerance based on a statistical signal model to nd out the minimum number of iterations to be executed in the CORDIC algorithm. We adopt the pipeline strategy to fulfill the CORDIC iterative operation for the efficient usage of hardware resources. Beam pattern simulation results indicate that the proposed system achieves satisfactory performance for beam focusing. Finally, we implement the CORDIC rotator on the Altera Stratix® FPGA to investigate its data processing capability and the consequent hardware savings compared with the complex multiplier by examining its critical path delay.