The characteristics of iris-fed millimeter-wave rectangular microstrip patch antennas

A model is proposed for describing the iris-fed patch antenna based on aperture coupling to cavities. A variety of iris-fed patch antennas are experimentally analyzed, and antennas with iris feeds of sizes ranging from 15 to 115 percent of the patch size are found to show a minimum VSWR of 5:1 in the waveguide. It is demonstrated that the resonant frequency of the antenna can be predicted with high accuracy using a formula related to the model explanation model, even when the iris is 15 percent larger than the path. Far-field power patterns were measured for antennas, and the maximum gain for any antenna was found to be 4.5 dBi, with a typical value of 2 dBi. Interference between the radiation from the patch and secondary radiation from the iris feed was noted for antennas having an iris of nearly the same, or greater, size than the patch.