Spectral domain analysis of microstripline fed arbitrarily-shaped aperture antennas

In microwave and millimeter-wave antennas systems, printed apertures have been widely used as radiating elements. They are also used frequently as coupling elements for a variety of application such as to excite a microstrip patch antenna. A distinct advantage of aperture-coupled antennas over conventional patch antennas is that the feeding structure can be hidden below the ground plane, such as the microstripline fed slot antennas. However, present techniques can only deal with the rectangular-shaped aperture antennas, such as rectangular slot antennas. As to the non-uniformly shaped aperture antennas, such as the exponentially-tapered slots and Archimedian spiral antennas, the existing modeling methods can not handle them well. As a result, a hybrid technique is developed by incorporating the reciprocity technique, with method of moments using triangular basis functions to model arbitrarily-shaped aperture antennas fed by a microstripline. Two types of arbitrarily oriented or offset aperture antennas, the rectangular slot and the exponentially-tapered slot antenna, are analyzed to show the validity of this hybrid technique.<>