A Miniaturized Reflectarray Antenna for Scanned Beam Applications

In this study, we propose a novel design method to significantly reduce the volume of reflectarray antennas. Unlike the commonly used approaches, the distance (F) between a source antenna and a reflectarray is largely narrowed in this work, which is no longer than 0.3 lambda. Accordingly, the total area occupied by the reflectarray can also be reduced with almost no decline in performance. Instead of a directional antenna, a simple omnidirectional dipole antenna is used as a feeding source, which has traditionally been expected to lower aperture efficiency of the proposed antenna. To solve this problem, an additional condition to maximize antenna gain in a target direction is suggested, which applies to both waves reflected from the reflectarray and radiated directly from the source. Moreover, by assuming that an incident plane wave coming from a far-field region, ambiguity in the polarization and incidence angle of the incident field impinging onto the reflectarray can clearly be removed. As a result, a relatively high aperture efficiency and antenna gain can be maintained in spite of the extremely reduced volume that is more than 700 times electrically smaller than the conventional ones. Good agreement between the experiment and the prediction confirms the validity of our approach.