Adaptive Impedance-Matching Techniques for Controlling L Networks

The link quality of mobile phones suffers from antenna mismatch due to fluctuating body effects. Techniques for adaptive control of impedance-matching L networks are presented, which provide automatic compensation of antenna mismatch. To secure reliable convergence, a cascade of two control loops is...

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Bibliographic Details
Published in:IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2010-02, Vol.57 (2), p.495-505
Main Authors: van Bezooijen, A., de Jongh, M.A., van Straten, F., Mahmoudi, R., van Roermund, A.
Format: Article
Language:English
Subjects:
Adaptive arrays
Adaptive control
Adaptive filters
Antennas
Automatic control
Convergence
Detectors
Feedback
Impedance
impedance matching
Mobile antennas
Mobile handsets
power amplifiers
Programmable control
switched-capacitor filters
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Summary:The link quality of mobile phones suffers from antenna mismatch due to fluctuating body effects. Techniques for adaptive control of impedance-matching L networks are presented, which provide automatic compensation of antenna mismatch. To secure reliable convergence, a cascade of two control loops is proposed for independent control of the real and imaginary parts of impedance. A secondary feedback path is used to enforce operation into a stable region when needed. These techniques exploit the basic properties of tunable series and parallel LC networks. A generic quadrature detector that offers a power-independent orthogonal reading of the complex impedance value is presented, which is used for direct control of variable capacitors. This approach renders calibration and elaborate software computation superfluous and allows for autonomous operation of adaptive antenna-matching modules.
ISSN:1549-8328
1558-0806
DOI:10.1109/TCSI.2009.2023764