Heightening upper limit frequency of wideband antenna using asymmetrical radiating elements

In recent years, cognitive radio system is receiving particular attention as a promising technology in order to materialize efficient network access. In this paper, heightening upper limit frequency of the wideband antenna for cognitive radio system was investigated by employing three types of the antenna element variations. As a result, the antenna, employing asymmetrical elements, with the VSWR less than 2.0 in the frequency range of 3.1 GHz to 18 GHz was obtained. As for the radiation patterns, although the slightly distorted radiation patterns due to employing the asymmetrical elements were observed, it is acceptable in practical use.