Optimization Design of Wideband Asymmetric Doherty Power Amplifiers

Abstract-In this paper, a wideband asymmetric Doherty poweramplifier is designed with a short stepped impedance transformer instead of a conventional quarter-wavelength impedance transformer. The Doherty power amplifier is applied with a drain voltage of 18 V for the main amplifier and 27V for the peak amplifier. When the output power is 40 dBm, the wideband asymmetric Doherty power amplifier covers a bandwidth of 225 MHz ranging from 1.8 GHz to 2.025 GHz. The gain flatness is between 0.5 dB and the power added efficiency (PAE) in the whole band is larger than 40%. The designed Doherty power amplifier achieves a 1 dB compression output power of 50.22 dBm with a maximum PAE of 59.13% at 1.9 GHz. At about 8 dB power back-off from the 1dB compression point (P1dB), the PAE is 53.02%, and at about 10 dB power back-off from P1dB, the PAE reaches 44.56%.