Abstract: A multi-channel parallel radiofrequency (RF) transmitter was developed for high-field magnetic resonance imaging (MRI) scanners. With a single field programmable gate array (FPGA) and a multi-channel digital analog converter (DAC), the transmitter can generate multi-channel RF pulses in parallel. The frequency, phase and amplitude of the RF pulses can be adjusted quickly and independently. The FPGA reads the parameters of the RF pulses previously stored in a dual-port random access memory (RAM), and uses them to carry out modulation and direct digital frequency synthesis (DDS) for each RF pulses, resulting in multi-channel digital RF signals. The digital signals were then converted into analog RF signals with a high-performance DAC. The use of intellectual property core provided by Xilinx greatly reduced development time, difficulty and cost in achieving the main functions of the transmitter, such as DDS and modulation. The developed multi-channel RF transmitter has the merits of high integration, small size, low cost and good universality, providing an efficient component for high field MRI systems.

Key words: MRI, multi-channel radiofrequency transmitter, high-field, field programmable gate array (FPGA), software defined radio