Wideband dual-polarised electromagnetic-fed patch antenna with high isolation and low cross-polarisation

A wideband dual-polarised patch antenna with high isolation and a low cross-polarisation level is presented. Two orthogonal linearly-polarised modes are excited by the electromagnetic-fed structure. One of the two modes is excited by a pair of hook-shaped probes with a 180o phase difference; while the other is excited by a magnetic-coupled loop, which is comprised of a metal loop and an open-ended transmission line. By introducing two shorting pins, the isolation between two feeding ports can be enhanced to more than 40 dB. Moreover, the radiation patterns in the ± 45° planes have a cross-polarisation level of less than -30 dB within the 3 dB beam widths. The measured -10 dB reflection coefficients bandwidth of the two modes are 40.7% (2.45-3.7 GHz) and 38.7% (2.6-3.85 GHz). The gains of the proposed antenna are about 8.7 and 9.1 dBi over the operating band. Thus, this antenna is highly suitable for the base station antenna that is required to cover the operating bandwidth of 3.5 GHz WiMAX systems.