Aperture-coupled microstrip antennas using reflector elements for wireless communications

The design advantages provided by aperture-coupled microstrip patches can be very useful in wireless communications applications. A way to improve the front-to-back ratio is to place a microstrip antenna element behind the aperture as a reflector. Proximity coupling between the feed line and the reflecting element is negligible due to the thick foam substrate used, allowing use of the reciprocity method of analysis. Also, the directive patch elements are shielded from the reflector by the ground plane. Therefore, only interactions between the reflector and the aperture need to be modeled, resulting in a simple analysis. For aperture-coupled patch designs with a front-to-back ratio of 10 dB or greater, the introduction of a reflecting element has a negligible effect on the input impedance of the antenna. Therefore, a reflector element can readily be incorporated into existing designs.