Adaptive digital predistortion for linearization of power amplifier
Author
Şekerlisoy, Burak
Advisor
Atalar, Abdullah
Date
2009Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
In most communication systems, power amplifiers are used to obtain high output
power. The nonlinear characteristics of the power amplifier leads to the distortion
of the output signal. This distortion affects the efficiency of the power amplifier.
The way to reduce this effect is to linearize the power amplifier near the saturation
region where it is nonlinear. The widely used technique for the linearization
of power amplifiers is predistortion. The proposed technique for predistortion
uses a LUT(look-up-table), a complex multiplier, an address calculator, delay
elements and an adaptation logic. A new adaptation logic to update the LUT
coefficients, is used. The predistorter is simulated in Matlab software using a
baseband model for the power amplifier. 16-QAM baseband modulation is used
to simulate the predistorter. In order to see the performance of the proposed
predistorter, hardware logic is implemented in FPGA and experimental setup
with RF circuits and RF power amplifier is used. For different LUT sizes, the
algorithm is tested and for the LUT size of 64, nearly 15 dB improvement in
power spectrum is observed. The LUT size of 64 is observed to be the optimal
LUT size in the experiments.
Keywords
Adaptive Digital PredistortionLook-up Table Predistortion
Linearization
Amplifier Nonlinearity
FPGA