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Abstract #2638

An Envelope-Tracking Transmit Array Amplifier

Pascal P. Stang1, John M. Pauly1, Greig C. Scott1

1Electrical Engineering, Stanford University, Stanford, CA, United States

Modern MRI pulse sequences demand high-fidelity RF transmit reproduction at multi-kilowatt power levels. Typical MRI power amplifiers are Class-AB architectures which excel at predictable linear performance, yet become inefficient when used at less than their peak power. We present an envelope-tracking linear RF power amplifier system to explore the potential efficiency gain and performance impact of this method in the context of MRI transmit arrays. The efficiency improvement from envelope tracking varies with both pulse shape and amplitude, however for sync pulses, preliminary measurements show DC power consumption reduced by 20-35% compared to operation at full supply rail while delivering the same RF output.