Adaptive Predistortion Using a Delta Sigma Modulator for Automatic Inversion of Power Amplifier Nonlinearity
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Boo-2009-Adaptive Predistorti.pdf
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Author(s)
Boo, Hyun Ho
Chung, SungWon
Dawson, Joel L.
Alternative Title
Adaptive Predistortion Using a ΔΣ Modulator for Automatic Inversion of Power Amplifier Nonlinearity
Date Issued
December 2009
Journal
IEEE Transactions on Circuits and Systems. II, Express Briefs
Publisher
Institute of Electrical and Electronics Engineers
Citation
Boo, H.H., Sung Won Chung, and J.L. Dawson. “Adaptive Predistortion Using a \Delta \Sigma Modulator for Automatic Inversion of Power Amplifier Nonlinearity.” Circuits and Systems II: Express Briefs, IEEE Transactions on 56.12 (2009): 901-905. © 2009 Institute of Electrical and Electronics Engineers
Version
Final published version
Abstract
Abstract—This brief demonstrates a new adaptive digital predistortion
architecture particularly suited to mobile handset applications.
The central idea is to build a lookup table (LUT) that
directly captures the static compressive nonlinearity of the power
amplifier (PA) and then insert this LUT into the feedback path of a
ΔΣ modulator. The oversampled ΔΣ modulator automatically
performs both the inversion of the PA nonlinearity and the interpolation
between LUT entries, permitting complex modulation
strategies to be handled with an absolute minimum of LUT entries
and with a dramatically simplified computational structure. The
advantages of this architecture over previous methods include:
1) there is no need to explicitly invert the PA nonlinearity, reducing
the complexity for the system designer; 2) the LUT training is
done with an open-loop method, improving the training speed;
3) there is no need to explicitly employ numerical interpolation
between LUT entries; and 4) digital-to-analog converter (DAC)
nonlinearity is incorporated into the predistortion, allowing fast
low-resolution DACs to be used in the final system. We built a
proof-of-concept prototype for a 900-MHz, 27-dBm PA transmitting
a 16-ary quadrature amplitude modulation (16-QAM) signal
with a bandwidth of 3.4 MHz. The predistortion system reduced
out-of-band distortion products by 10 dB and improved the error
vector magnitude from 3.5% to 2.0%.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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DOI of Published Version
http://dx.doi.org/10.1109/TCSII.2009.2035269
