Dual-Polarized Duplex Patch Antenna Based on a Multiport Ring Feeding Structure

This letter presents a dual-polarized duplex patch antenna using a multiport ring feeding circuit. The ring circuit consists of four input ports and four output ports. When one input port of the ring circuit is excited, the four output ports form two pairs of differential ports accordingly. First, a four-port wideband patch antenna is developed using this ring feeding circuit. The four output ports of the ring circuit are directly connected to four metal strips and then coupled to the patch radiator. Once any one of the four antenna ports is excited, wide operating bandwidth covering the base-station band 1710–2690 MHz can be obtained. Second, a dual-polarized duplex patch antenna is realized by connecting the four antenna input ports to two pairs of bandpass filters. For different requirements, the center frequencies of the two duplex operating bands can be tuned to desired ones within 1710–2690 MHz using specified filters. For demonstration, a prototype of the dual-polarized duplex antenna operating at 2.0 and 2.6 GHz is implemented. Better than 26 dB measured isolation between all the four ports is realized.