Multiband Response Investigation for Stub-Loaded Right-Angled Isosceles Triangle Microstrip Antenna

Abstract

Two multiband configurations, one using right-angled isosceles triangle patch included with stubs and another using semicircular patch embedded with a slot along with stubs fabricated on a thicker substrate of glass epoxy, were reported. The first configuration gave triple-band operation at 3.5 GHz, 2.45 GHz and 1.96 GHz with respective gains of 7.5, 7.9 and 5.8 dBi, while the second also gave triple-band operation at 5.5 GHz, 3.5 GHz and 2.45 GHz with respective gains of 1.8, 1.5 and 1.2 dBi. Conversely, an explanation of resonant modes that results in multiband operation was not given for any of the configurations. In this paper, a detailed investigation explaining the triple-band response of one of the reported works, right-angled isosceles triangle patch, is presented using resonance curve plots, return loss plots and its surface current distributions. It is observed that length variations of stubs integrated with patch antenna modify the various frequencies modes in such a way that yields multiband response. The position and dimensions of stubs with given feed result in matched input impedances at TM10, TM21 and TM30 modes of the triangular patch those results into triple-band response.