Effect of substrate material on radiation characteristics of an UWB antenna

This article highlights the effect of substrate material on radiation characteristics of an ultra wideband antenna. Printed monopole antennas fabricated on a substrate offer impedance band width which can cover UWB. However radiation pattern varies significantly over the bandwidth. The cross polar component increases with frequency and the pattern degrades from the desired omnidirectional characteristics. Structures are designed using different substrate thickness of different materials and radiation characteristics are compared. Omnidirectional radiation bandwidth can be increased significantly by decreasing the substrate thickness and using substrate material of low dielectric constant. Structure with foam substrate is designed, fabricated and tested. The measured VSWR is <; 2 over 3.1-10.6 GHz frequency band. The antenna offers high efficiency and its radiation patterns indicate the suitability of this antenna for UWB applications.