A Miniaturized Ring Slot Antenna Design With Enhanced Radiation Characteristics

The design of a miniaturized CPW-fed ring slot antenna using interdigitated slits is presented. The fundamental resonant frequency of the ring slot antenna was reduced significantly using an interdigitated slit-loaded structure. A further reduction in resonant frequency to 54.46% of the unloaded resonant frequency of the ring slot antenna was also achieved using multiple interdigitated slits inside the ring, causing the antenna to almost reach the electrically small limit. Thereafter, the antenna characteristics of the electrically small antenna is significantly enhanced using a low impedance metamaterial slab design working under normal incidence, leading to a considerable reduction in superstrate height. Particularly, the directivity and efficiency of the electrically small antenna is significantly improved with the incorporation of the low-profile superstrate. In addition, good matching characteristics are obtained for the miniaturized antenna without the necessity of a matching network together with improved bandwidth.