Development of a Modular FPGA Based Digital Beamformer for PC Based Ultrasound Imaging System

Abstract

A digital transmit and receive beamformer for PC based ultrasound imaging was developed. This system consists of an analog front end, FPGA control board, ultrasound probe, and computer. Analog front end consists of programmable pulser and receiver circuit. The pulser circuit uses high voltage pulse generator to produce monocycle electrical pulses with the adjustable center frequency and amplitude up to 50 V. The receiver circuit uses a AD9272 chip, which is an 8-channel integrated analog front end module. Each of the 8 signal paths consists of a low noise amplifier (LNA), a digitally programmable variable gain amplifier (VGA), anti aliasing filter (AAF), and a 12-bit, 40 Mega Samples Per Second (MSPS) analog-to-digital converter (ADC). The probe is a 64 element linear probe which can produce pulses with center frequency of 3.5 MHz. The Xillinx Spartan 6 FPGA based beamformer consists of 8 channel transmit beamformer controller block and 8 channel receive beamformer blocks. The receive beamformer is composed with delay stage block, apodization blok, summation block, Hilber transform block, and envelope detection block. The implementation result shows that the system was able to process the RF signals.