A Printed Vivaldi Antenna with Improved Radiation Patterns by Using Two Pairs of Eye-Shaped Slots for UWB Applications

In this paper, a printed Vivaldi antenna with two pairs of eye-shaped slots is proposed for UWB applications. By using two pairs of eye-shaped slots, the side lobe levels of the radiation pattern are reduced, and the antenna gain is improved at low frequencies. To illustrate the effectiveness of the proposed design, a prototype of the proposed antenna is fabricated and measured. Experimental results show that the proposed antenna presents a measured impedance bandwidth, defined by [absolute value of [S.sub.11]] < -10dB, from 3 to 12.8 GHz with a compact size (36mm x 36 mm). Good unidirectional radiation characteristics with a front-to-back ratio better than 10 dB are also achieved. The measured gain is better than 3.7dBi in the operating frequency band. In addition, the measured group delay of the proposed antenna is around 1.2 ns with a variation less than [+ or -]0.5 ns.