A New Adaptive Digital Predistortion Technique Employing Feedback Technique

We have developed a new adaptive digital predistortion linearization technique based on RF feedback predistortion (FBPD). By combining the feedback linearization and digital predistortional linearization techniques, the performance of the predistorter is enhanced significantly compared to the conventional digital PD. To clearly explore the characteristics of the digital FBPD, we have compared it to the conventional digital PD based on recursive least-square (RLS) algorithm. For demonstration, Doherty and class F amplifiers are linearized using the proposed digital FBPD. For a 2.14-GHz forward-link WCDMA signal, the ACLRs at 2.5-MHz offset of the Doherty and class F amplifiers are -57.5 dBc and -51.4 dBc which are improved by 20 dB and 27 dB at average output power of 43 dBm and 33 dBm, respectively. The new algorithm could linearize the class F amplifier with high nonlinearity.