Design of a Stub-Loaded Ring-Resonator Slot for Antenna Applications

A T-shaped stub-loaded ring-resonator (SLRR) slot etched on the ground plane or on the radiating patch has been designed and analyzed for antenna applications. Compared with the conventional ring slot, the two resonant frequencies of the proposed SLRR-slot can be lowered, and can also be tunable by varying the parameters of the four T-shaped stubs. To validate the design concept, a tri-band printed antenna and a dual band-notched ultra-wideband (UWB) antenna using the SLRR-slot on the ground plane and radiating patch, respectively, are presented. For the tri-band antenna, a simple U-shaped slot etched on the microstrip feeding line is used to excite a third upper-frequency band independently without increasing the overall size of the antenna and without affecting the lower two bands. The proposed tri-band antenna has three frequency bands of 2.4, 3.5, and 5.8 GHz, and the dual band-notched UWB antenna can guarantee a very wide bandwidth from 3.0 to 12.0 GHz with dual undesired bands successfully. The experimental results including radiation patterns, peak gains and efficiencies of both antennas are presented.