Variations of Slot Cut and Stub Loaded Square Microstrip Antenna for Circular Polarization

Abstract

Modified technique to produce circular polarization for square, nearly square microstrip antenna using diagonal slots of different shapes, slits, stub at corners of antenna is proposed. Diagonally embedded slots are perpendicular to stubs which yield orthogonal modes to give circular polarization. In-depth explanation for orthogonal mode degeneration using different slots shape, its impact on various antenna parameters and sense of rotation is discussed. VSWR, axial ratio bandwidth greater than 38% and 4.1% is obtained respectively. Resultant gain and cross polar level is 8 and 23 dBi. Antenna parameters are compared for square, nearly square microstrip antenna for different slot shapes. Major contribution of paper is empirical formulation of resonant frequencies corresponding to orthogonal modes from its surface current distribution. Close agreement is observed between simulated and calculated resonant frequency from proposed formulations.