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Summary: IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 49, NO. 12, DECEMBER 2001 2507
Gain/Phase Imbalance-Minimization Techniques
for LINC Transmitters
Xuejun Zhang, Student Member, IEEE, Lawrence E. Larson, Fellow, IEEE, Peter M. Asbeck, Fellow, IEEE, and
Peter Nanawa
Abstract--Two simple calibration schemes for the correction of
the path imbalance in a linear amplification with nonlinear com-
ponents (LINC) transmitter have been demonstrated. In the fore-
ground algorithm, a baseband digital signal processor (DSP) eval-
uates the gain and phase imbalance with a set of calibration signals,
while in the background algorithm, the imbalance is characterized
by exchanging the two LINC vector components. In both cases,
the compensation of the path imbalance is accomplished within
the DSP by introducing a predistortion term. A prototype LINC
system has been tested for CDMA IS-95 baseband input, and 38
and 35-dBc adjacent channel interference were achieved for the
foreground and background schemes, respectively. The quadra-
ture errors of the in-phase/quadrature modulators set a limit on
the overall performance of both algorithms.
Index Terms--Amplifier linearization, LINC, mobile communi-
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