Compact and high efficiency Doherty power amplifier using a new modulation load range

We propose a new modulating load range for a Doherty power amplifier (DPA) that will maintain maximum drain voltage swing and consequently peak efficiency in over 6-dB power back-off (PBO). At 6-dB PBO, the real part of the new modulating load seen by the main amplifier is less than 2*Ropt. The new load range allows for the design of a compact, low loss output matching and combiner circuit and a simple single drain bias line for the main and auxiliary amplifiers. The proposed 2-stage DPA using the new modulating loads is designed at 15 GHZ in a 0.15 μm enhancement mode (E-mode) Gallium Arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process. The proposed DPA achieves a measured Psat of 27 dBm, a peak power added efficiency (PAE) of 41% and a PAE of 34% at 6 dB PBO with a gain of 17 dB.