Enhanced gain and broadband of endfire antenna by using I-shaped resonator structures

Abstract

A broadband high-gain periodic endfire antenna is presented in this article. The broadband is achieved by using a planar out-of-phase power divider with ultra-wideband performance and periodic dipole elements. The device uses two substrates with a common ground plane. A coupling between two microstrip lines on the top and bottom substrate layers through a slot in the common ground plane, and a transition from two microstrip lines to a parallel stripline are used to achieve an ultra-wideband operation. The gain enhancement is achieved by loading with an I-shape resonator (ISR) structure in the endfire direction. The effect of the I-shape unit cell structure on the gain enhancement is investigated. Both the ISR-loaded antenna and unloaded one are fabricated to verify the predictions. The measurements show that ISR-loaded antenna presents gain of about 7 dB-10 dB in the whole working band (3 GHz-11 GHz), which is about 2 dB-3.5 dB more than the unloaded one. The proposed antenna can be using in wireless communication systems for its advantages of broad bandwidth and high-gain.