Extending the Inverse Model Range of Applicability for Efficient Predistortion of Wideband Envelope Tracking Amplifiers

An improved modeling strategy that extends the inverse model range of applicability (RoA) is applied in this paper. The Rational Generalized Memory Polynomial (RGMP) inverse model based, digital predistortion (DPD) is utilized on a high efficiency wide bandwidth envelope tracking (ET) power amplifier (ETPA) for wideband carrier aggregated (CA) signals. This ET configuration is specifically designed for a variety of wideband CA signals that have up to 500MHz corrected bandwidth. Term selection is performed with Doubly Orthogonal Matching Pursuit (DOMP) using <40 terms of hundreds, while achieving improved spectral emissions, with computational efficiency, output signal fidelity and improved power efficiency. The bench has a Gen 3, Xilinx ZCU208 RFSOC, for the signal generation and RGMP DPD. We evaluated a variety of 2CA (PAPR=4.2dB) and 4CA (PAPR=6dB) signals with up to 500MHz signal bandwidth on a Wolfspeed CG2H40025 GaN RFPA between 3.4-3.9GHz. With the extended RoA, the specific 4CA signals, with PAPR=6dB with 480MHz bandwidth achieve Po>40dBm, DE>34% and <-35dBc spectral regrowth with RGMP DPD and Adagio™ ET signals.