Multi-Mode Cavity-Backed Slot Ring Antenna for Multi-band Applications

This paper presents a multi-mode approach for designing multi-band cavity-backed slot antennas. The approach is based on the analysis of the fundamental and first higher-order mode of a slot ring structure. In addition, cavity modes can be introduced by adding a floating reflector underneath the slot at a small distance of around one-eleventh wavelength, which is much less than the conventional requirement for quarter-wavelength separation distance. The first higher-order mode of the slot can be controlled by placing, at particular locations, one or more capacitors inside the slot. Simulated IEEE gains of the designed antennas are around 9 dBi over the entire frequency band of 900 MHz-3 GHz. Prototypes and measurements will be further detailed.