Highly Linear and Efficient Microwave GaN HEMT Doherty Amplifier for WCDMA

ETRI Journal, Volume 30, Number 1, February 2008 ABSTRACT⎯A highly linear and efficient GaN HEMT Doherty amplifier for wideband code division multiple access (WCDMA) repeaters is presented. For better performance, the adaptive gate bias control of the peaking amplifier using the power tracking circuit and the shunt capacitors is employed. The measured one-carrier WCDMA results show an adjacent channel leakage ratio of -43.2 dBc at ±2.5-MHz offset with a power added efficiency of 40.1% at an average output power of 37 dBm, which is a 7.5 dB back-off power from the saturated output power.