Dual-Band Reflection-Type Circular Polarizers Based on Anisotropic Impedance Surfaces

• Published in: IEEE transactions on antennas and propagation 2016-02, Vol.64 (2), p.826-830
• Main Authors: Fartookzadeh, M., Mohseni Armaki, S. H.
• Format: Article
• Language: English
• Subjects: Antenna measurements; Arrays; Bandwidth; Circular Polarization; Dual band; Dual Frequency; Electromagnetic bandgap structures; Frequency selective surfaces; Polarization; Surface impedance
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2015.2511152

A new method for constructing dual-band linear to circular polarization (CP) converter is introduced based on anisotropic impedance surfaces. An air gap is used between the substrate and ground plane to control the operating frequency of the surface without changing the substrate thickness. Required susceptance of the surface to produce CP is calculated using the equivalent transmission line model. The surface consists of small-size patches inside slotted large patches to construct a circular polarizer with two frequency bands: 1.9-2.3 GHz and 7.9-8.3 GHz. Sizes of the patches are obtained using analytical formulas. In addition, it is indicated that the permitted beamwidth of the incident wave can be increased by reducing the propagation angle {{\theta}}. The circular polarizer with reduced {{\theta }} has 52% and 9.8% bandwidths for less than 3 dB axial ratio with {{{\theta }}_{{\bf max}}} = 39^\circ and {{{\theta }}_{{\min}}} = 25^\circ . Finally, comparison between LHCP and RHCP radiation patterns of an antenna with the proposed circular polarizer indicates more than 10 dB difference throughout the main lobe.