Fully Integrated Asymmetric Doherty Amplifier Based on Two-Power-Level Impedance Optimization

Abstract

A fully integrated asymmetric Doherty power amplifier has been developed by using GaN HEMT MMIC technology. To minimize the circuit size, a two-power-level impedance optimization method was applied instead of using a quarter-wavelength transmission line impedance inverter for load modulation in the Doherty amplifier. For this optimization, asymmetric configuration is required to realize optimum impedance conditions. The 4-GHz-band GaN HEMT Doherty amplifier MMIC exhibited a maximum drain efficiency of 56% and a maximum power-added efficiency (PAE) of 53% at 4.3 GHz, with a saturation output power of 36dBm. In addition, PAE of 44% was achieved at 4.2 GHz on a 6-dB output back-off condition.