Genetic optimization of microstrip reflectarrays

Printed reflectarrays try to combine the advantages of both reflectors and printed arrays (see e.g. [l]) and consist in arrays of printed patches, illuminated by a primary feed horn, that re-radiate the illuminating power back into the space. Since the elements have different positions, the field that propagates from the feed to the patches covers different path lengths and therefore the contributions to the total re-radiated field coming from the different patches are not in phase. So it becomes necessary to adjust the phase of the single element to compensate the different path lengths and this may be obtained using at least one of the following different possible techniques: adding to the patches suitable differentlength transmission lines [2, 31, varying the size of the radiating elements [4], rotating the elements to different angles or finally varying the dielectric constant of the material below the radiator itself. Here we chose to combine the first two options together.