Multimode resonant microstrip antennas with electrically small patch and frequency scannable circularly polarised angle

Abstract

Semi-analytical design approach to electrically small, dual-mode resonant, wideband circularly polarised (CP) microstrip annular sector patch antenna (MASPA) with variable polarization is proposed for satellite-assisted Internet-of-vehicle (IoV). At first, the upper bound of electrically small patch is theoretically laid down by advancing an interpolated algorithm to the eigen-roots of the characteristic equation, so that the radius of patch can be rapidly determined in the initial design step. In this way, MASPA with electrically small patch, multimode resonant, and frequency scannable CP angle can be yielded. Dual-mode resonant MASPAs with flare angles of 330° on air substrate, and 270° on suspended microstrip air/F4B substrates having a profile less than 0.05-wavelength are then numerically studied and experimentally validated. In the suspended microstrip case, MASPA with maximum patch radius of 0.159-wavelength (electrically small), equal impedance and tilted CP bandwidths up to 26.6%, and tilted CP angle of θ_t = −10°–35°, has been successfully implemented. Therefore, the proposed approach should be highly effective for low-profile, electrically small, wideband CP antenna designs.