RF Reconfigurable Predistorter for Power Amplifiers

Hyunil KANG  

IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.9   pp.1664-1669
Publication Date: 2007/09/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.9.1664
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technology)
Category: Active Devices/Circuits
power amplifier,  multimode,  multiband,  AM to AM,  AM to PM,  predistorter,  

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This paper presents data on a reconfigurable predistorter for compensating the nonlinearity of a power amplifier in a system supporting both multimode and multiband operations. For compensation, the magnitude and phase response of a predistorter should be easy to tune to match that of a nonlinear amplifier that is used in various standards. That is to say, the predistorter should show decreasing magnitude followed by increasing magnitude, and the phase must initially lag and then lead, or lead and then lag, as a function of the increasing power input. In doing so, the power turning point, gain & phase deviation, and phase lead & lag should easily be controlled by the proposed reconfigurable predistorter using a bias control and impedance transformer. These characteristics are provided by the nonlinearity of the FET and the movement of the bias point caused by negative current generation. This proposed predistorter can be adopted for a system that uses Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA) 800 MHz, and CDMA 1800 MHz. For example, by adopting this reconfigurable predistorter in a CDMA 1800 MHz, as much as 14 dB improvements in Adjacent Channel leakage Power Ratio (ACPR) at the 4 dB back off power level, can be achieved for the CDMA 1800 MHz signal.