Decoupling Design of Quad-Polarization Overlay Antenna Element With a Stacked Structure

This letter presents a design to decouple a quad-polarization antenna element without diodes. It consists of a bottom patch for orthogonally polarized elements and an upper patch twisted at 45° for slant polarized elements. The mutual coupling between the two antennas is reduced by the side wall of the upper element and conductor posts to maintain the distance between the two antennas. The posts also function as an electrical shield of the feeding cable to the upper antenna. The simulation results show that at an antenna height of 0.38λ, the proposed antenna can reduce mutual coupling to less than −15 dB. The measurement results match the simulation results.