A Gate Modulated Digitally Controlled Modified Class-E Amplifier for On-Coil Applications in 1.5 T MRI

A novel technique of modulating both the amplitude and frequency of the desired MR Radiofrequency pulse in a class-E amplifier topology, without utilizing supply-modulation, is presented. Amplifier’s MATLAB model is developed and the carrier frequency bitstream is intelligently controlled to achieve both the amplitude and phase modulation of the output waveform. Benchtop experiments are performed showing accurate translation of software predictions on hardware, however requiring some additional optimization steps. MR experiments are performed to demonstrate the slice-selective capability of the generated RF pulse. Images are acquired at input powers of up to 80 W with 89% peak drain efficiency.