High-efficiency X-band MMIC GaN power amplifiers with supply modulation

This paper presents measurement results on supply-modulated X-band 0.15μm gate width GaN HEMT MMIC power amplifiers for OFDM signals. Two PAs at 10GHz with 4 and 10W output powers show peak CW efficiencies of 69% and 55%, with gains of 8.5 and 20.4 dB respectively. Supply modulation trajectories are designed by static characterization of each MMIC PA, and the drain modulation is performed though both a linear broadband modulator and a high-efficiency 5-MHz switching modulator. The PAs are tested in four modes: (1) with a constant 20-V supply and the 18-MHz OFDM signal input through the drive; (2) pure envelope tracking; (3) signal-split supply modulation; and (4) envelope elimination and restoration (EER) with a 5-MHz switching modulator. Average PAE and composite power added efficiencies are compared, reaching 65.4% and 35%, respectively, with the 4-W PA and a linear modulator.