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International Journal of Antennas and Propagation
Volume 2012, Article ID 858031, 8 pages
http://dx.doi.org/10.1155/2012/858031
Research Article

Analysis of Circular Polarization of Cylindrically Bent Microstrip Antennas

Department of Electronics, Tampere University of Technology, P.O. Box 692, 33101 Tampere, Finland

Received 13 March 2012; Accepted 18 May 2012

Academic Editor: Thomaskutty Mathew

Copyright © 2012 Tiiti Kellomäki. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

When circularly polarized (CP) microstrip antennas are bent, the polarization becomes elliptical. We present a simple model that describes the phenomenon. The two linear modes present in a CP patch are modeled separately and added together to produce CP. Bending distorts the almost-spherical equiphase surface of a linearly polarized patch, which leads to phase imbalance in the far-field of a CP patch. The model predicts both the frequency shifting of the axial ratio band as well as the narrowing of the axial ratio beam. Uncontrolled bending is a problem associated especially with flexible textile antennas, and wearable antennas should therefore be designed somewhat conformal.