Review of reconfigurable vivaldi antennas

In recent trends, the developments of multi-mode terminals have received great attention and have increased in popularity. Single terminals or devices could have many applications such as, GPS, GSM, WLAN, Bluetooth, etc. To suit such applications wideband, multi-band or reconfigurable antennas have been developed. However when considering the interference levels at the receiver, reconfigurable antennas are the best option, since only one single band is used at a given time. Wideband-narrowband reconfiguration is essential for future wireless communications i.e. cognitive radio, since they employ wideband sensing and reconfigurable narrowband communications. A Vivaldi antenna which is inherently wideband is a good prospect for doing this is. During the operation, most of the current is flowing at the very edge of the tapered profile. Therefore stopping the current can easily be done by perturbing the tapered slot edge. Works on band notching of Vivaldi antenna have been reported in [1] and [2] recently. In [1] a U-shaped slot was employed to notch out the 5.1 – 5.8 GHz WLAN band while in [2] a λ/4 short stub was inserted into a radiating region to cut-off the 5.05–5.93 GHz band. However to the best of the authors' knowledge, no attempt has yet been reported on reconfiguring the operating band of Vivaldi antenna except work by [3] and [4]. In this article, we show 4 different approaches on how to reconfigure the Vivaldi operating band. The first approach employed multiple defected ground structures (DGS) in different positions. The second approach employed a single set of DGS with switchable length. The third approach used combined rectangular and ring shaped DGS. The final approach used a microstrip line resonator concept. The first three approaches shows band pass reconfiguration and the final approach shows band notch reconfiguration.