Discrete Supply Modulation of a Three-Stage K-Band PA

A three-stage K-band GaN MMIC amplifier with over 20 dB of saturated gain, greater than 4W peak output power, and a peak PAE over 40% is characterized using supply modulation. A discrete supply modulator is used to track the 50MHz noise-like signal used for testing. Drain supply modulation increases the efficiency by 9 percentage points and, through the use of a flat-gain shaping function, does not degrade the linearity compared to the static supply case for the same output power. An adaptive shaping function for the discrete supply modulator further improves supply modulation performance in back-off. This work demonstrates an improvement in efficiency without the need for pre-distortion and, to the best of the authors' knowledge, is the first demonstration of supply modulation on a GaN PA at K-Band.