Dual-Polarized Filtering Antenna with High Selectivity and Low Cross Polarization

This paper presents a dual-polarized patch antenna with quasi-elliptic bandpass responses. The proposed antenna is mainly composed of a feeding network, a driven patch, and a stacked patch, with its entire height being 0.09λ. The feeding network consists of two orthogonal H-shaped lines that coupled to the driven patch, each for one polarization. The elaborately-designed feeding lines not only ensure a sharp roll-off rate at the lower band edge, but also help to achieve low cross polarization and high isolation between two feeding ports. On the other hand, the upper stacked patch provides improved suppression levels at the upper stopband and also an enhanced gain within passband. Consequently, a compact dual-polarized antenna with satisfying filtering performance is obtained, without using extra filtering circuits. For demonstration, an antenna is designed to fit the specification of LTE band (2.49-2.69 GHz). The implemented antenna achieves an average a gain of 9 dBi, a cross-polarization ratio of 29 dB, an isolation of 35 dB within LTE band. The out-of-band suppression level is more than 40 dB within the 2G and 3G frequency bands from 1.71-2.17 GHz. It can be used as the antenna elements in multiband base station antenna arrays to reduce the mutual coupling.