Compact Band-Rejected Ultrawideband Slot Antennas Inserting With $\lambda /2$ and $\lambda /4$

Two compact ultrawideband (UWB) slot antennas with band-rejected characteristics are proposed for UWB communication applications. The entire size of both antennas is as small as 15 mm × 22 mm × 0.8 mm, which is smaller than most of the proposed UWB antennas. The radiator is a stepped slot excited by a 50 Ω feed line. By etching a half-wavelength and a quarter-wavelength slot from the ground plane of UWB slot antennas, respectively, two UWB antennas with band-notched characteristics can be obtained. The potential interference between UWB and WLAN/WiMAX can be reduced. Omnidirectional radiation patterns and constant gain can be observed in the pass bands. Time-domain characteristics of both proposed antennas are analyzed under different conditions. It demonstrates that the time-domain characteristics of the antennas are good enough for UWB applications. The results show that proposed antennas are very suitable for various portable UWB systems.