Loaded Multi Loop Hexagram Shaped Printed Antennas for Multifrequency Communication

Structurally novel ‘Hexagram’ shaped microstrip loop antenna variants are reported here which provide multiple bands in the useful frequencies ranging from S to K-band. This design yielded at least six resonances with 51% bandwidth at C, X & Ku and 18.4% at K band. Reactive loading of the patches provided better impedance matching with respect to $50\Omega$ coaxial input, over X to K band. The proposed antenna exhibits compactness as compared to the conventional ones due to its efficient space-filling nature supporting loop current paths in a short physical length. Here the basic geometry is a structure, which is the initiator of the multi-loop current path generation. Several higher order modes were excited in the antennas due to the uniqueness of the geometrical structure leading to multimodal loop currents. Concepts of characteristic mode theory were utilized to get an insight into the current modes generated on the structure due to the premeditated placement of the feed point. It is to be noted that the intuitive choice of feed location has matched with characteristic mode analysis for determining the resonant frequencies. The above has been further determined with CST microwave studio simulation. A comparative study of reported multiband antennas shows that the antenna presented here is showing significant betterment.