Patch Antennas With Loading of a Pair of Shorting Pins Toward Flexible Impedance Matching and Low Cross Polarization

Patch antennas with loading of a pair of shorting pins are proposed in this paper toward flexible impedance matching and low cross polarization. The shorting pins are introduced in the centerline of a square patch to strengthen the surface current density near the feeding point at edge. As these paired pins simultaneously move away from the center toward the two radiating edges of patch, the resonant input impedance of the microstrip-edge-fed patch antenna is increasingly reduced due to enlarged current density at the feeding point. Because of symmetric arrangement of these two shorting pins, surface current density on the patch is maintained as the odd-symmetric property with respect to the H-plane, thus tremendously degrading the cross-polarization level. Simulated and measured results are found in good agreement with each other in terms of input impedance and radiation pattern. They further demonstrate that co-polarization to cross-polarization ratio (CTCR) of the paired-pins-loaded patch antenna in H-plane is maintained at least 10 dB higher than that of its single-pin-loaded patch counterpart.