Compact Dual-Polarized Filtering Antenna Based on Differential Feeding and Double-Layer Metasurface

compact dual-polarized filtering antenna with differential feeding and double-layer metasurface is investigated. The proposed filtering antenna consists of a pair of suspended crossed dipoles, a double layer metasurface, eight off-center metalized vias, and four center-shorted square split rings (CS-SSRs). By utilizing the double-layer metasurface and the off-center metalized vias, a radiation null is realized in the upper and lower stopbands, respectively. Besides, two more radiation nulls are obtained at the two band edges by loading CS-SSRs beside the crossed dipoles, which further suppresses the radiation level in the stopbands and improves the frequency selectivity. The performance of the proposed filtering antenna is verified by both simulation and measurement. It exhibits a 20.7% (4.31-5.32 GHz) measured impedance bandwidth with a compact aperture size of 0.56 lambda(0) x 0.56 lambda(0). (lambda(0) is the free-space wavelength at 4.8 GHz.) The measured in-band average gain achieves 6 dBi with suppression levels in the lower and the upper out of-bands reaching 18.4 and 21.5 dB, respectively.