Dual-Feed Dual-Polarized Patch Antenna With Low Cross Polarization and High Isolation

A dual-feed dual-polarized microstrip antenna with low cross polarization and high isolation is experimentally studied. Two different feed mechanisms are designed to excite a dual orthogonal linearly-polarized mode from a single radiating patch. One of the two modes is excited by an aperture-coupled feed, which is comprised of a compact resonant annular-ring slot and a T-shaped microstrip feed line; while the other is excited by a pair of meandering strips with a 180deg phase differences. Both the linearly-polarized modes are designed to operate at 2400 MHz frequency band, and from the measured results, it is found that the isolation between the two feeding ports is less than 40 dB across a 10 dB-input-impedance bandwidth of 14%. In addition, low cross polarization is observed from the radiation patterns of the two modes, especially at the broadside direction. Simulation analyses are also carried out to support the measured results.