Increasing Bandwidth of Slot Antennas With Combined Characteristic Modes

This communication finds that it is the combined characteristic modes (CMs), rather than the purely magnetic ones, that are always associated with low-resistance resonances of slot antenna. Thus, combined CMs could help control its bandwidth. A ring slot antenna with loaded stubs is proposed and analyzed to show how to use combined CMs to explain and achieve wideband characteristic. It is shown that by loading stubs, a new combined CM is introduced. A prototype antenna is then fabricated to experimentally validate the analysis and designing approach. The fractional bandwidth of the proposed ring slot antenna could be effectively increased from 12.5% to 18.2%.