A wide-band dual-polarization patch antenna with directional coupler

A broad-band dual-polarization patch antenna fed by L-shaped probes at the patch corners is presented. A coupled line directional coupler mounted at the back of the ground plane is used to enhance the isolation between the L-probes to a large extent. Through using the coupler to feed the L-probes, the isolation between the input ports is 34 dB over the GSM900 operating bandwidth, which has enhanced by 14 dB. By using two plastic spacers of 0.1/spl lambda//sub o/ in height to support the patch in the air, an impedance bandwidth of 18% (for S/sub 11//spl les/-14 dB), and an average gain of 7 dBi can be obtained for both ports. The far field patterns are stable across the passband. This antenna can potentially be used as a GSM900 base station antenna.