Stacked-patch Dual-Band & Dual-Polarized Antenna with Broadband Baluns for WiMAX & WLAN Applications

In this paper, a dual-band antenna in orthogonal polarization with stacked configuration is proposed. The proposed antenna introduces two layers of radiating patches to realize the dual frequency characteristic. A pair of novel 180 degrees broadband microstrip baluns, printed on the backside of the bottom substrate, are utilized to feed the antenna. By employing wideband feeding mechanisms for the two input ports, high input port isolation and wide impedance bandwidth are successfully realized. The proposed antenna is fabricated and measured. It exhibits a characteristic of two resonant frequencies. The lower band f(1) is from 2.75 to 4.01 GHz with a relative bandwidth of 37.3% and over 8.1 dBi gain at two ports, and the upper band f(2) is from 4.4 to 5.21 GHz with a relative bandwidth of 16.9% and over 5.8 dBi gain at two ports. The port isolation is below -35 dB, and the cross-polarization level is below -20 dB at broadside across the whole band.