Power amplifier for magnetic resonance imaging using unconventional Cartesian feedback loop

In MRI systems, RF fields are affected by the presence of the human body in the scanner causing mismatch between the RF coil and the feed cable. A power amplifier incorporating an unconventional Cartesian feedback loop is presented which works to maintain a fixed current in the RF coil against impedance variations. The performance of the system is investigated by model simulation, including stability analysis, linearity improvement and mismatch compensation. A prototype amplifier is measured to verify the model.