Multiband microstrip antennas fed by an L-probe

This paper presents microstrip antennas (MSAs) for multiband operation fed by an L-probe. The proposed antennas consist of a double-layered dielectric substrate. Patch elements are on the top surface of the upper substrate and the L-shaped probe is in the lower substrate. V-shaped slots on a rhombic MSA and multiple-ring MSAs are effective for multiple resonances. In order to realize wideband impedance matching, an L-shaped probe or a modified L-shaped probe is used to excite these patch elements. The rhombic MSA with V-shaped slots and the multiple-ring MSAs work as multiband planar antennas for linear polarization and for combination of linear and circular polarizations, respectively. Multiband performance with good radiation patterns of these types of multiband MSAs are demonstrated. Furthermore, muliband MSAs fed by a modified L-shaped probe for linear polarization composed in a single-layer dielectric substrate are described.