Compact dual-polarized microstrip antennas

Dual linearly polarized operations of a compact slot-loaded square microstrip antenna are experimentally investigated in this paper. Four symmetrical bent slots are embedded in the square patch, and placed in parallel with the patch's central lines or diagonals to achieve lowered operating frequencies of the two linearly polarized radiations (0 and 90° polarizations ±45° slanted polarizations), which results in a reduced antenna size at a fixed operating frequency. Experimental results show that, for such a compact dual-polarized microstrip antenna with an inexpensive FR4 substrate, isolation between the two feeding ports better than 35 dB can easily be obtained, which is also better than that of a corresponding unslotted dual-polarized square microstrip antenna. In addition, the cross-polarization level in the E- and H-plane patterns for the compact dual-polarized microstrip antenna studied is about as good as that of an unslotted square microstrip antenna.