Derivative-Based Envelope Design Technique for Wideband Envelope Tracking Power Amplifier with Digital Predistortion
YI Xueya1, CHEN Jixin1,CHEN Peng1,NING Dongfang2, YU Chao1
(1. State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China;
2. ZTE Corporation, Shenzhen 518057, China)
Abstract: A novel envelope design for an envelope tracking (ET) power amplifier (PA) based on its derivatives is proposed, which can trade well off between bandwidth reduction and tracking accuracy. This paper theoretically analyzes how to choose an envelope design that can track the original envelope closely and reduce its bandwidth, and then demonstrates an example to validate this idea. The generalized memory polynomial (GMP) model is applied to compensate for the nonlinearity of ET PA with the proposed envelope design. Experiments are carried out on an ET system that is operated with the center frequency of 3.5 GHz and excited by a 20-MHz LTE signal, which show that the proposed envelope design can make a good trade-off between envelope bandwidth and efficiency, and satisfactory linearization performance can be realized.
Keywords: bandwidth reduction; envelope tracking; shaping function; supply modulator
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