Broadband Dual-Polarized Filtering Antenna with Wideband and Deep Out-of-Band Suppression

A wideband dual-polarized cross-slot antenna (CSA) with wideband out-of-band suppression is first presented. Then, a new bandpass filter with wideband harmonic suppression is cascaded with the CSA to achieve further out-of-band gain suppression. By adjusting the length of the cross-slot lines to operate in half a wavelength, a radiation zero can be generated at the low frequency. To improve the upper stopband selectivity in the high frequency, four V-shaped slots are etched under the feeding lines, and four controllable radiation nulls can be introduced. Without any filtering circuits, the dual-polarized CSA realizes a wide impedance bandwidth (IMBW) of 1.60-2.95 GHz (59.34%) and out-of-band gain lower than -11.4 dBi across 3.20-9.12 GHz (up to 4.01 f₀). Then, a broadband bandpass filter with five controllable transmission nulls is designed and cascaded with the filtering CSA to further improve the out-of-band suppression. Finally, cascading with the harmonic-suppressed bandpass filter, the realized gain of the antenna is below -16.8 dBi across 3.05-10.92 GHz (up to 4.79 f₀). For demonstration, two filtering antennas are implemented. Reasonable agreement between the measured and simulated results is observed. © 1963-2012 IEEE.