Studies of small dualband annular‐ring slot antenna with a pair of implanted spur‐like slits

In this article, a compact annular‐ring slot antenna for dualband operations is proposed and studied. A pair of spur‐like slits was implanted in the center patch of an annular‐ring slot antenna to excite two resonant modes with their resonant frequencies easily adjusted by changing the dimensions of these slits, resulting in a large range of dual‐frequency ratios (1.07–2.2). For the first excited resonant mode, the routes of the equivalent magnetic current distribution in the slot region can be lengthened by these slits. The resultant lowered first resonant‐band center frequency (from that of the unperturbed annular‐ring slot antenna) thus made the proposed antenna effectively miniaturized. The proposed antenna was found to have very good linearly polarized broadside radiation patterns and very low cross polarization levels in both operating bands.