Compact 40% Fractional Bandwidth Doherty PA with Input Group Delay Engineering

This paper presents a wideband Doherty power amplifier design based on the control of the relative input group delay between the carrier and peaking amplifier. By reaching an appropriate input phase variation over the target bandwidth, frequency dispersion of load modulation is minimized and a less dispersive DPA at peak power is achieved. To validate this approach, a compact DPA with 50 dBm peak power is developed and shows an average drain efficiency greater than 44% and a gain greater than 12 dB at 8 dB of Output Back-Off (OBO) over 1.8 to 2.7 GHz which represents 40% fractional bandwidth. Linearization of the prototype is proven using DPD correction with ACPR below -60 dBc measured in single band scenarios. Moreover, under 400 MHz of instantaneous bandwidth, the proposed DPA achieves ACPR below -53 dBc with average efficiency of 48%.