Novel shaping function for envelope tracking linearization

Envelope tracking (ET) linearization can be explained as the cancellation between two kinds of intermodulation distortions (IMD) [1]. A novel shaping function for ET linearization can thus be constructed by balancing the two IMDs. A dynamic approach of shaping function extraction, called slope tuning, is proposed and demonstrated in this study. Significant linearity improvements in a heterojunction bipolar transistor (HBT) power amplifier are experimentally achieved with extracted shaping function for both two-tone and long-term evolution (LTE) signals.