Abstract
In this article, two coplanar waveguide-fed high gain multiband antennas with and without uniplanar copper strip-based electromagnetic band gap (CS-EBG) structure are proposed for portable wireless applications at 2.1, 2.4, 3.5, 5.2, 5.4, and 5.8 GHz. The initial multiband antenna is realized by patch-ground shape modification and open-ended rectangular slot insertion on the patch. The two layer uniplanar CS-EBG structure is composed of square ring periodic elements of copper strips of different widths and gaps. The top unit cells are placed at an offset position with respect to the bottom layer, which is new technique applied to obtain multiple resonances from such a simple and compact planar structure. The antenna, when combined with the CS-EBG structure, still preserved its multiband characteristics and produced directional pattern because of the reflecting property (like artificial magnetic conductor, AMC) of the CS-EBG/AMC structure behind it, which was donut and omnidirectional shape in case of the antenna alone. The initial antenna gain is 5 dBi while the final antenna gain is improved to approximately 12 dBi at the first band and more than 6 dBi at other bands. Thus, the developed square ring copper strip structure is very effective to improve the antenna performances and finally resulted in a high gain antenna. Both of the configurations with and without the CS-EBG/AMC are fabricated and tested, and the measurements are well agreed with the simulations. Despite of the slight frequency shifting, the antenna is still suitable for the portable wireless operation such as Wi-Fi, WiMax, WLAN/HIPERLAN and even for LTE/4G technology at some frequencies. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1608-1614, 2015