High-Efficiency RF Power-Amplifier Module for Magnetic-Resonance Imaging

Frederick H. Raab¹, Martin C. Poppe², Daniel P. Myer³

This amplifier system is based upon the Kahn EER (envelope-elimination-and-restoration) technique. The amplifier system incorporates class-E RF-power amplifiers, class-S modulators, and a digital signal processor. The DSP includes capability for generating stored signals as well as digitizing and amplifying low-level analog RF inputs. The module incorporates four RF-power amplifiers and can produce up to 750 W with an overall efficiency of 70 percent. It has a bandwidth of 250 kHz and an envelope rise time of 1 s, and can be configured for operation between 10 and 128 MHz.