Design of Broadband Endfire Antenna with Split-ring Resonator(SRR) Structures

A broadband high gain endfire antenna is presented in this paper. Broad bandwidth is realized 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 split-ring resonator (SRR) structure in the endfire direction. The effect of the SRR-shape unit structure on the gain enhancement is investigated. Both SRR-loaded antenna and unloaded one are fabricated to verify the predications. The measurements show that SRR-loaded antenna presents gain of about 7dB-10dB in the whole working band (3.5GHz-11GHz) ,which is about 2dB-4.5dB more than the unloaded one. This antenna can be used in wireless communication systems for its advantages of the broad bandwidth and high gain.