A Wideband Differentially Fed Dual-Polarized Antenna With Wideband Harmonic Suppression

A wideband differentially fed dual-polarized antenna with wideband harmonic suppression is presented. The radiating structure is composed of open slots, stair-shaped strips, and a square patch. To realize symmetrical radiation and low cross-polarization for orthogonal polarizations, eight open slots are etched on the four corners of the square patch. Stair-shaped strips are not only used to excite the open slots, but also introduce the monopole resonance. In addition, patch resonance is excited on the center square patch. To match these different resonances, shorted microstrip lines are utilized to achieve the wide impedance bandwidth. Moreover, compact stepped impedance resonators are elaborately introduced on the top of the patch to achieve wideband harmonic suppression without any increase of the antenna footprint. To verify the design method, the proposed antenna is designed, fabricated, and measured. Measured results demonstrate that the proposed antenna has the impedance bandwidth of 1.70-2.81 GHz for Sdd11 < -15 dB with high isolation of 39 dB. Moreover, wideband harmonic suppression is measured from 3 GHz to 9 GHz with the Sdd11 higher than -2.2 dB and the corresponding harmonic gain lower than -5.3 dBi. In addition, stable gain of 7.2-7.9 dBi and beamwidth of 63-71º are achieved for base station applications.