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A New Predistorter Using Low Frequency Intermodulation Signals Injection of a Harmonic Generator
Young KIM Hyung Soon JANG Sung Uk KIM Ik Soo CHANG Yong Chae JEONG
IEICE TRANSACTIONS on Electronics
Publication Date: 2003/08/01
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microwave and Millimeter Wave Technology)
predistorter, linearizer, vector modulator, power amplifier, harmonic generator,
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In this paper, a predistorter using low frequency intermodulation (IM) signals is proposed. The harmonic generator of the proposed predistorter that consists of a hybrid coupler and four diodes biased separately extracts a second order low frequency IM signal. And with multiplication of second order IM signals, fourth order IM signal is obtained. A vector modulator, modulate fundamental signal with low frequency IM signals, generates predistortion IM signals and controls amplitude/phase of them with modulation factors. As a result, this predistorter is suppressed individual order intermodulation distortion signals of power amplifier effectively. The suggested predistorter has been manufactured to operate in Korea PCS base-station transmitting band (1840-1870 MHz). The test results show that the third order IM is cancelled more than 20 dB and the fifth order IM is cancelled about 10 dB for CW two-tone signals. Also, it's improved the adjacent channel power ratio (ACPR) more than 10 dB for CDMA (IS-95) signals.