Comparison of S-band Analog and Dual-Input Digital Doherty Power Amplifiers

Abstract

This work aims at assessing the performance improvement offered by a dual-input digitally driven Doherty power amplifier (DPA) with respect to the single-input topology. To this aim, an analog DPA is designed and characterized. The equivalent digital version, which only differs by the absence of the input power divider, is also realized and analyzed. This ensures a fair comparison of the two topologies. Power-dependent input signal splitting between the main and auxiliary branches as well as adaptive phase alignment are adopted in the digital version to compensate for the back-off efficiency degradation as well as other shortcomings typically shown by traditional analog DPAs. For the first time, the performance figures of merit of the equivalent analog and digital DPAs are compared one-to-one systematically. The comparison over the 3.1-3.7 GHz range shows a superior efficiency performance of the digital DPA over the analog one, both at saturation and in back-off. Furthermore, the dual-input control also ensures higher gain and saturated output power.