A 2 W GaAs Doherty power amplifier for WiMAX applications

This paper presents a GaAs Doherty power amplifier (DPA), designed and implemented at 5.6 GHz, for WiMAX applications. The designed DPA uses two identical 1 W packaged GaAs HEMTs for the main and peaking amplifiers. A maximum output power of 34.4 dBm (2.8 W) was measured, with a maximum power-added efficiency of PAE = 31% (η = 42%). The efficiency was maintained higher than PAE = 23% (η = 29%), over 6 dB of output back-off range, and higher than PAE = 16% (η = 21%) over 10 dB output back-off. The linearity performance of the designed Doherty PA was experimentally tested with a 9-carrier, 64-QAM digitally modulated signal with a peak-to-average-power ratio of PAR = 9.6 dB. An adjacent-channel-leakage ratio of ACLR = -33 dBc was measured at an average output power of P_{out, avg.} = 24 dBm. To the best knowledge of the authors, this is the first Doherty PA designed and implemented in the 5 - 6 GHz frequency range, in hybrid technology.