Multiband ring microstrip antennas fed by an L-probe in a single-layer substrate

This paper presents multiband microstrip antennas (MSAs) fed by an L-shaped probe in a single-layer substrate. Multiple squared split ring MSAs with concentric arrangement and an L-probe to excite them are constructed in a dielectric substrate. The split ring MSAs can radiate linear polarization at a resonant frequency of the respective MSAs and the L-probe is used for wideband impedance matching to the MSAs. Therefore, this antenna serves as a linearly polarized multiband planar antenna. Furthermore, multiple squared ring MSAs with truncated corners are formed by using both sides of a dielectric substrate for circularly polarized multiband operation. In this paper, multiband performance with good radiation patterns as well as low cross polarization of the proposed antennas is demonstrated.