Techniques in Low-IF, Low Power MRI Front Ends

Motivation: Wearable MRI receive arrays are hindered by bulky cabling, and cable traps to support off-coil signal/data transfer. This impacts patient workflow and handling. Goal(s): Our goal is to identify low power techniques for balun-free receive chains that could potentially be located on the array. Approach: We have prototyped image reject low power mixers, PCB planar transformers, and low intermediate frequency active op-amp anti-aliasing filter topologies for use with a SAR ADC. Results: Fully differential op-amp antialiasing filters achieve under 30mW power, and perform >500kHz bandpass anti-aliasing at 1.25 MHz low-IF. Image rejection exceeds 40dB for only 14-18mW. Distributed on-coil signal chains are feasible. Impact: If the front end electronics can be distributed on the coil array, this opens the possibility of data transmission with a wireless interface. The receive topology could eliminate cable trap baluns, which inhibit flexibility and wearability, compromising form factor.