Formulation of Resonant Length for Triple Band Slot Cut Stub Loaded Rectangular Microstrip Antenna

The multi band microstrip antenna is realized either by placing stub on the edges of the patch or by cutting slots at an appropriate position inside the patch or by using the combination of these two methods. In this paper an analysis to study the effects of stub and slot in dual stub loaded and stub loaded pair of rectangular slot cut rectangular microstrip antennas is presented. The additional stub or slot reduces the resonance frequency of higher order mode of the single stub loaded patch and along with the modified modes of stub loaded rectangular patch, yields triple frequency response. Further by studying the surface current distributions at modified modes of the rectangular patch, a formulation in resonant length in terms of stub and slot dimensions is proposed. The frequencies calculated using the proposed formulations agrees closely with the simulated results. The proposed study gives an insight into the functioning of slot cut and stub loaded antennas and proposed formulations can be used to design them at give frequencies.