Digital Predistortion for Envelope-Tracking Power Amplifiers Using Decomposed Piecewise Volterra Series

• Published in: IEEE transactions on microwave theory and techniques 2008-10, Vol.56 (10), p.2237-2247
• Main Authors: Anding Zhu, Draxler, P.J., Chin Hsia, Brazil, T.J., Kimball, D.F., Asbeck, P.M.
• Format: Article
• Language: English
• Subjects: Amplifiers; Applied sciences; Behavioral modeling; Circuit properties; Decomposition; Design. Technologies. Operation analysis. Testing; Digital; Distortion; Dynamics; Electric, optical and optoelectronic circuits; Electronic circuits; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; envelope tracking (ET); Exact sciences and technology; Integrated circuits; Integrated circuits by function (including memories and processors); linearization; Nonlinear distortion; Nonlinearity; Peak to average power ratio; power amplifier (PA); Power amplifiers; Power system modeling; predistorter; Predistortion; Radio frequency; Radiofrequency amplifiers; RF signals; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Studies; Thresholds; Voltage; Volterra series; Wireless communication
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2008.2003529

Due to dynamic changes of supply voltage, envelope-tracking (ET) power amplifiers (PAs) exhibit very distinct characteristics in different power regions. It is very difficult to compensate the distortion induced by these amplifiers by employing conventional digital predistortion techniques. In this paper, by introducing a new piecewise Volterra model based on a vector threshold decomposition technique, we first set several thresholds in the input power level according to the PA characteristics, and decompose the input complex envelope signal into several sub-signals by using these thresholds. We then process each sub-signal separately by employing the dynamic deviation reduction -based Volterra series, and finally recombine them together to produce the predistorted output. Experimental results show that by using this new decomposed piecewise digital predistorter model, the distinct characteristics of the ET system at different signal power levels can be accurately modeled, and thus, the distortion, including both static nonlinearities and memory effects, caused by the amplifier nonlinear behavior can be effectively compensated.