A microstrip reflectarray using crossed dipoles

Microstrip reflectarrays offer a flat profile and light weight, combined with many of the electrical characteristics of reflector antennas. We describe the use of crossed dipoles as reflecting elements in a microstrip reflectarray. The theory of the solution is described, with experimental results for a 6" square reflectarray operating at 28 GHz. The performance of crossed dipoles is directly compared with microstrip patches, in terms of bandwidth and loss. We also comment on the principle of operation of reflectarray elements, including crossed dipoles, patches of variable length, and patch elements with tuning stubs. This research was prompted by the proposed concept of overlaying a flat printed reflectarray on the surface of a spacecraft solar panel. Combining a solar panel and antenna apertures in this way would lead to a reduction in weight and simpler deployment, with some loss of flexibility in independently pointing the solar panel and the antenna. Using crossed dipoles as reflectarray elements will also minimize the aperture blockage of the solar cells, in contrast to the use of elements such as microstrip patches.