A Constant Gain Ultra-Wideband Antenna with a Multi-Layer Frequency Selective Surface

An ultra-wideband (UWB) antenna with a novel multi-layer frequency selective surface (FSS) reflector is presented. A significant enhancement in the gain has been achieved in a low profile design while maintaining the excellent impedance bandwidth of the UWB antenna. The average peak gain of the antenna has been increased from 4 dBi to 9.3 dBi as a consequence of the use of the FSS reflector. More importantly the gain variation within the frequency range from 3 GHz to 15 GHz is only ±0.5 dB. This is a significant improvement from ±2 dB gain variation of the UWB slot antenna without the reflector. This optimized FSS reflector provides the exibility of mounting a planar antenna close to conducting bodies, including screens and cases.