Design of high efficiency Doherty power amplifier applying power controlling technology with 15dB output power back-off
A novel method to design Doherty power amplifier (DPA) with promoted high efficiency performance in a very large output power back-off (OBO) is proposed in this paper. By reduce the variation range of the optimized output impedances of the carrier power amplifier (PA), the pit area in the efficiency carves are improved. Applying the nonlinearity of radio frequency schotty barrier diodes (SBDs), the convention power divider (PD) before DPA is replaced with a non-fixed power-split-ratio PD. Especially for very large OBO applications, when the carrier PA is chosen at a much smaller power level than the peak PA, the performance at the whole OBO could be promoted more apparently. For verification, a DPA with 15dB OBO was designed at the center frequency of 2.56GHz. The maximum measured drain efficiency (DE) at saturation output power 43.6dBm are over 77%, and achieved minimum DE of 58% during the whole 15dB OBO.