A programmable FPGA-based 8-channel arbitrary waveform generator for medical ultrasound research activities.

In modern ultrasound imaging systems, digital transmit beamformer module typically generates accurate control of the amplitude of individual elements in a multielement array probe, as well as of the time delays and phase between them, to enable the acoustic beam to be focused and/or steered electronically. However, these systems do not provide the ultrasound researchers access to transmit front-end module. This paper presents the development of a digital transmit beamformer system for generating simultaneous arbitrary waveforms, specifically designed for research purposes. The proposed architecture has 8 independent excitation channels and uses an FPGA (Field Programmable Gated Array) device for electronic steering and focusing of ultrasound beam. The system allows operation in pulse-echo mode, with pulse repetition rate of excitation from 62.5 Hz to 8 kHz, center frequency from 500 kHz to 20 MHz, excitation voltage over 100 Vpp, and individual control of amplitude apodization, phase angle and time delay trigger. Experimental results show that this technique is suitable for generating the excitation waveforms needed for medical ultrasound imaging researches.