FPGA implementation of Delta Sigma Modulation based all-digital RF transmitter for parallel magnetic resonance imaging

This paper presents an all-digital RF transmitter which enables frequency, phase, and amplitude modulation in a magnetic Resonance Imaging (MRI) system. Delta Sigma Modulation (DSM) is a very promising technique to generate digital modulated signals and gaining high interest for all-digital transmitter architectures in MRI. In an all-digital MRI transmitter, the switch mode RF power amplifiers amplifies the digital signal with high efficiency; and a narrowband RF coil filters the digital signal to recover the envelope information. So, high efficiency is maintained through the RF chain up to the RF coil. All-digital transmitter architecture seems a good candidate to a parallel MRI system. In this study, a novel delta sigma based digital modulator is proposed. Multi-band signal modulation with less than 1 Hz inter-carrier frequency resolution and digital single side band modulation with 50 dB side band suppression are achieved with the new modulator.