Active Coil Decoupling by Impedance Synthesis using Frequency-Offset Cartesian Feedback

Pascal P. Stang¹, Marta Gaia Zanchi¹, Adam Kerr¹, John Mark Pauly¹, Greig C. Scott¹

Transmit coil arrays are subject to mutual coupling and loading variations, while RF power amplifiers exhibit non-linearity, ill-defined output impedances, and memory effects. We examine and successfully demonstrate Frequency-Offset Cartesian Feedback (FOCF) as a method to address these challenges, showing improved RF amplifier linearity, output impedance manipulation, and active coil decoupling in MR images. Corrections are performed using only an in-line vector coupler at the RF amplifier, with no on-coil sensor needed. Tuning for active decoupling and stability sensitivities are discussed.