Novel Dual-Band Equal-Cell Doherty Amplifier Design With Extended Power Back-Off Range

In this article, for the first time, a new and generalized design methodology for dual-band Doherty power amplifier (DPA) is presented. Owing to the adoption of equal-cell architecture and extended power output back-off (OBO > 6 dB) operation, the conventional dual-band impedance-transformer approach cannot be applied. Because of this, a novel output combiner is proposed for the provision of load modulation at two widely spaced frequency bands. For verification, a 9-dB-OBO DPA with 1.4- and 3.5-GHz operating frequencies is designed and fabricated. Simulation and measurement results indicate excellent Doherty efficiency behavior with back-off (9 dB) efficiency of over 55% and saturation efficiency of over 68% at both frequencies. Under 9-dB-peak-to-average power ratio (PAPR) WCDMA signal excitation, average efficiency of 52.1% and 51.3% is achieved at 1.4 and 3.5 GHz, respectively.