A Compact and Broadband Doherty Power Amplifier Without Post-Matching Network

Post-matching network (PMN) dominates broadband Doherty power amplifier (DPA) design, but at the cost of large footprint. This brief presents a PMN-free, compact and broadband DPA based on dual-mode impedance transformer (IT) which can simultaneously realize a complex-to-real conversion at two frequencies. The conversion ratio of the IT is significantly increased while its fluctuation is reduced after collaborating a short drain bias. The dual-mode ITs are used as the output matching networks in the carrier and peaking paths. An out-of-phase 2nd harmonic injection path is constructed based on the inherent structure of the IT without additional bridge, resulting in enhanced saturated efficiency and output power at the upper band edge. A prototype circuit operating from 2.1 to 3.1 GHz is fabricated, and measured results show a 7-8.2 dB gain and 42.2-43.3 dBm output power at saturation. The 6-dB OBO and saturated efficiency is 42.3-52% and 60.4-67.7%, respectively. The area of the whole OMNs is only 19× 37 mm2, indicating a significant size reduction, while the DPA’s performance is comparable with the PMN types.