Linear Tapered Slot Antenna with Defected Side for Improved Gain

Linear tapered slot antennas (LTSAs) have been widely investigated as typical examples of coplanar antennas because the LTSAs offer the advantages of wide impedance bandwidth, high gain, and easy fabrication [1], [2]. However, they have high back lobes in the E-plane [3]. In general, the LTSAs are very sensitive to the thickness and the width of their supporting substrate. It is shown that radiation patterns of a tapered slot antenna (TSA) is affected on magnetic currents induced in the edge of the finite width of a substrate [4]. This degradation of the radiation pattern, which is caused by the small width of an antenna aperture, is a significant problem on a compactness of TSA [5]. A corrugation structure at edges of TSA for decrement of degradation has reported in [6]. However, the effect of a corrugation structure proposed in [6] is not enough to improve an antenna gain. In this paper, a new LTSA with defected sides are proposed for gain improvement. The defected sides are similar to a conventional dumbbell-shaped defected ground structure (DGS) which has been used for microwave circuit application such as a filter implementation. The proposed defected side-LTSA (DS-LTSA) is designed to suppress unwanted magnetic currents which result in a radiation to a backward direction of the antenna. The results of simulation and experiment show that the proposed antenna has a gain improvement due to preventing of oppositedirected magnetic currents.