Formulation of Resonant Length for Triple Band Rectangular Microstrip Antennas

The triple band stub loaded U-slot or rectangular slot cut RMSAs are discussed. The stub reduces the resonance frequency of TM02 mode of the patch and along with TM10 mode yields dual band response. Further, an analysis to study the effect of slot on the triple band response in stub loaded rectangular micro strip antenna is presented. The surface current distributions and radiation pattern plots were studied. The U-slot or rectangular slot reduces the resonance frequency of next higher order TM12 mode of the patch and along with the modified TM10 and TM02 modes yields triple band response. By studying the surface current distributions, a formulation in resonant length at modified TM10, TM02 and TM12 modes is proposed. The frequencies calculated using the proposed formulations agrees closely with simulated results with % error less than 5% over the complete slot length range.