High efficiency Class-E tuned Doherty amplifier using GaN HEMT

This paper describes the design and fabrication of a highly efficient switching-mode class-E Doherty power amplifier using gallium nitride (GaN) high-electron mobility transistor (HEMT) for S-band radar applications. Measured results of the Doherty amplifier show power-added efficiency (PAE) and drain efficiency of 62.6% and 73.1% at 37 dBm of 6 dB output back-off point from saturated output power at 2.85 GHz, compared with PAE and drain efficiency of 42.9% and 44.7% for the case of balanced amplifier. It was found that PAE was improved by 19.7% by adopting the Doherty efficiency enhancement technique.