A compact wide-slot UWB antenna with reconfigurable and sharp dual-band notches for underlay cognitive radio applications

This paper presents a compact wide-slot ultrawide-band (UWB) antenna with reconfigurable and sharp dual-band notches compatible with the underlay cognitive radio systems. The antenna slot and tuning stub are reshaped in such a way that the proposed antenna operating bandwidth extends along the frequency band specified for UWB applications (3.1-10.6 GHz). In spite of their sharpness, the generated band notches perfectly cancel the interference with the entire 5 GHz wireless local area network (WLAN) frequency band (5.15-5.725 GHz) and that of the military X-band satellite communications downlink (7.25-7.745 GHz). The WLAN band notch is presented by attaching a pair of quarter wavelength parasitic elements to the antenna ground plane, while the other band notch is produced by engraving another pair of half wavelength parasitic elements within the antenna wide slot along the circumference of the antenna tuning stub. The reconfiguration of the band notches is achieved by inserting a pair of PIN diodes for each pair of parasitic elements. The simulated and measured results accentuate the UWB coverage of the proposed antenna, and also verify the reconfigurability and the sharpness of the antenna band notches. Moreover, the antenna has a noticeably stable radiation pattern over the entire band of operation with omnidirectional pattern convenient for portable UWB gadgets.