Understanding the appearance of specular reflection in offset fed reflectarray antennas

This paper provides an understanding of the mechanisms which give rise to specular reflections in offset fed reflectarray antennas. Offset fed reflectarray antennas incorporating variable length dipole type radiating elements have been designed. Each reflectarray is designed with a different dipole width in order to expose more or less of the underlying ground plane which gives rise to the specular reflections. The effect the amount of ground plane exposure has on the pattern performance is clearly illustrated and a plot which can aid in the efficient design of offset fed reflectarray antennas is given.