Compact circularly polarized microstrip array antenna

This article first presents a compact circularly polarized single patch antenna. The radiating structure consists of a square patch with embedding four bent slots to reduce the overall dimensions. Circular polarization is obtained by feeding the patch with 90° phase shift between two pins placed symmetrically on the two main axes. Wilkinson power divider is used to produce the λ/4 phase difference between the two feeding points and placed on the opposite side of the patch's ground plane. Then, a compact circularly polarized microstrip array antenna with four square patches is presented. The four patches are fed in phase quadrature such that a phase shift of 90° exists between each neighboring patches, thus providing circularly polarized pattern. The array feeding network is placed on the opposite side of the patches' ground plane and is designed using three Wilkinson power dividers having different output lengths that achieve the required phase shift between patches. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:604–609, 2011; View this article at wileyonlinelibrary.com. DOI 10.1002/mop.25772