Wideband Design of a Triple-Band Multi-Ring Microstrip Antenna Fed by an L-probe with Stubs

This paper presents wideband design of a triple-band multi-ring microstrip antenna (MR-MSA) fed by an L-probe with stubs. The proposed antenna consists of a quadruple-layered dielectric substrate. Three square ring patches are situated at the first to third layers from the top of the substrate for triple-band operation. A feeding L-probe to excite the three patches is arranged in the bottom layer with a large thickness for wideband design. In order to realize wideband operations for three bands, the structural parameters including the thicknesses of the layers of the substrate are tuned by using the numerical simulation with Mentor IE3D. Furthermore, the L-probe with stubs is used to improve the reflection characteristics. The design frequencies of the proposed antenna are around 3.6 GHz, 4.6 GHz, and 6.0 GHz. The simulated results reveal that fractional bandwidths of the three bands less than –10 dB reflection are 5.3%, 3.9%, and 14.3%, respectively. It is also confirmed by the simulation that stable unidirectional radiation patterns are obtained for the three bands.