Design of a Triple-band and Wideband Multi-Ring Microstrip Antenna fed by an L-probe

This paper presents design of a triple-band and wideband multi-ring microstrip antenna (MR-MSA) fed by an L-probe. The proposed antenna consists of two ring patches, a square patch, and an L-probe to excite the patches arranged at different layers of a quadruple-layered dielectric substrate. The design frequencies are 3.5 GHz, 4.75 GHz, and 7.5 GHz. The two ring patches and the one square patch for the lower middle, and higher bands are placed at the first to third layers of the substrate from the top, respectively. The L-probe is situated at the bottom layer on the ground plane. By using a thick substrate for the L-probe and optimizing the other dimensions, triple-band and wideband performance can be obtained. In this paper, the triple-band and wideband MR-MSA for the three target frequencies aforementioned is designed by using numerical simulation with Zeland IE3D. A PTFE substrate with a relative dielectric constant of 2.6 is used for the designed MR-MSA. By choosing 4.8 mm thickness for the bottom layer of the substrate and 7.8 mm overall height of the MR-MSA, fractional bandwidths of less than -10 reflection are predicted to be 11.3%, 4.6%, and 4.5% for the first to third bands, respectively.