WLAN band-notched printed U-shape UWB antenna

In this paper, we propose a low cost, compact printed U-shape ultra-wideband antenna with WLAN band-notched characteristics. The proposed antenna is a simple U-shape monopole structure with rectangular ground plane. The band-rejection characteristic is achieved by introducing a spiral shaped λ/4 open stub in the microstrip feed line to prevent interference due to WLAN systems operating within ultra-wideband. To achieve the desired UWB response with WLAN band notched characteristic, length and width of stub, spacing the stub, and the gap between the ground plane and the radiating structure are optimized. Frequency rejection characteristics depend on the shape and dimension of stub and can be fine controlled using other parameters. The antenna structure is designed, fabricated and tested. The simulation results show that the VSWR <; 2 from 2.8-11.4GHz with band stop characteristics in 5-6.1 GHz frequency band. The structure exhibits nearly omnidirectional radiation patterns, stable gain, and small group delay variation over the desired frequency bands.