Dual-polarized radiation is an important subject in patch antenna designs and can find applications in wireless communications systems that demand polarization diversity. Many related designs using the aperture-coupled feeding technique with the use of two crossed narrow slots or two offset narrow slots have been reported. However, due to the backward radiation, this kind of designs using two aperture-coupled feeds has the problem of increased port coupling when a conducting reflecting plate is added below the ground plane for practical applications. This is mainly because the reflecting plate and the ground plane may form a waveguide and some propagation modes may exist. In this article we propose new designs of broadband ual-polarized patch antennas fed by hybrid feeds of an aperturecoupled feed and a gap-coupled feed (see Fig. 1) or an aperture-coupled feed and a capacitively coupled feed (see Fig. 2). For these hybrid feeding designs, since the gap-coupled feed or the capacitively coupled feed has no backward radiation, their possible port coupling with the aperture-coupled feed in the region between the ground plane and the reflecting plate will be eliminated, which facilitiates the design problem when a reflecting plate is required for practical applications. Also, for the proposed antennas with a thick air substrate studied in this article, the 10-dB return-loss impedance bandwidths for the two polarizations can both be greater than 10percent and high isolation (> -30 dB) between the two feeding ports over the entire impedance bandwidth can be obtained. Good cross-polarization levels for the radiation patterns of the two polarizations are also observed.
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