Analysis and design of millimeter wave microstrip reflectarrays

The reflectarray combines features of reflector and array antennas. Reflectarrays are illuminated by a feed antenna which excites an array of radiating elements comprising a reflecting surface, and these elements produce a radiated field. Some types of reflectarrays, including the microstrip reflectarray, also produce a specularly reflected field component, as in the case of a reflector antenna. The total field then consists of the radiated field from the patches and the specular reflection. The design and analysis of two millimeter wave microstrip reflectarrays, operating around 27-28 GHz, are discussed. The first design utilises a corrugated conical horn feed and square patch radiating elements to accommodate dual polarisation. The main beam is steered to 25/spl deg/ off broadside in the vertical plane. The second design uses rectangular patches for linear polarization, and a backfire feed which greatly simplifies the feed supporting structure, and a broadside main beam. Measured patterns, gain, and a loss budget are presented and the performance is compared with typical microstrip array antennas. The generation of cross-polarized components of the radiated field is also discussed.