Broadband CMOS Stacked RF Power Amplifier Using Reconfigurable Interstage Network for Wideband Envelope Tracking

In this paper, a two-stage broadband CMOS stacked FET RF power amplifier (PA) with a reconfigurable interstage matching network is developed for wideband envelope tracking (ET). The proposed RF PA is designed based on Class-J mode of operation, where the output matching is realized with a two-section low-pass matching network. To overcome the bandwidth (BW) limitation from the high- Q interstage impedance, a reconfigurable matching network is proposed, allowing a triple frequency mode of operation using two RF switches. The proposed RF PA is fabricated in a 0.32- μm silicon-on-insulator CMOS process and shows continuous wave (CW) power-added efficiencies (PAEs) higher than 60% from 0.65 to 1.03 GHz with a peak PAE of 69.2% at 0.85 GHz. The complete ET PA system performance is demonstrated using the envelope amplifier fabricated on the same process. When measured using a 20-MHz BW long-term evolution signal, the overall system PAE of the ET PA is higher than 40% from 0.65 to 0.97 GHz while evolved universal terrestrial radio access adjacent channel leakage ratios are better than -33 dBc across the entire BW after memoryless digital pre-distortion. To our knowledge, this study represents the highest overall system performance in terms of PAE and BW among the published broadband ET PAs, including GaAs HBT and SiGe BiCMOS.