A Miniaturized CPW-Fed Spiral Ring Resonator Loaded Slot Antenna for Wireless Application

A simple and novel approach of size reduction of a slot antenna loaded with spiral ring resonator (SRR) on the patch surface is highlighted. The antenna resonates at 4.5 GHz when a half wavelength slot section is fed by the coplanar waveguide line. The fundamental resonant frequency is lowered by 2.05 GHz when the slot antenna is loaded with a pair of SRR at the end of the half wavelength slot section. The additional inductive and capacitive reactance of the resonator enables the patch to resonate at lower frequency (2.45 GHz). The proposed antenna structure reduces the resonant frequency with respect to the reference antenna (slot antenna without SRR) by 45.5%, causing the patch to almost reach an electrically small size. Finally, asymmetrical slot has been used and a wide band antenna of band width 900 MHz has been achieved. Despite the loaded patch touching the electrically small limit, the antenna needs no matching networks, offers high efficiency and exhibits a bandwidth better than the unperturbed patch. The radiation pattern is also seen to be unaffected by the presence of the SRR.