In the last decade, there is an increasing interest in printed reflectarray antenna, which combines the best features of traditional reflector antenna and conventional phased array antenna. Using microstrip technology these antennas are inexpensive and benefit from low profile nature of microstrip antennas. Recent advances in printed circuit and integrated circuit technology, as well as in computational electromagnetic analysis methods have led to improved design and optimization methodologies of such architectures which, in turn, have resulted in their increased deployment in communication system and radar applications. Usually a printed reflectarray antenna consists of a flat array of microstrip patches printed on a thin dielectric slab. A feed antenna illuminates the array whose individual elements are designed to scattered the incident field with proper phased required to form a planar phase surface in front of aperture. The phase of reflected wave is controlled by changing the geometrical parameter of elements. There are several methods for finding the relationship between changing the geometrical parameter of element and phase of its scattered field. In this thesis we explain different methods for finding this relationship. The adopted technique is assumption of local periodicity of element, so for finding the reflection amplitude and phase diagram of element, a single unit cell of a periodic infinite array of such elements analyzed by Ansoft HFSS software. The role and effect of different components of the reflectarray antenna such as elements, substrate, ground plane, feeder and etc. has been considered and explained. It has been observed that the reflection phase diagram of different types of elements, effect of substrate thickness and permittivity in reflection phase diagram of element, effect of array characteristic in aperture efficiency and effect of using an FSS as a ground plane of array on the reflected wave phase. The Reflectarray antenna suffers potentially significant loss due to dielectric loss, copper loss and surface wave excitation. These losses have been considered here. First we simulate one unit cell that already has been simulated and measured. As it will be seen the implemented simulations are closer to the measured data than the simulations have been published previously. We’ve also considered the effect of existence of losses in the reflection amplitude and phase diagram of the element. The considered element is a combined patch that is above the grounded lossy dielectric substrate. The used metal is copper. As we will see by increasing the loss tangent of the dielectric slab the losses increased. Also by changing the loss tangent the resonance frequency of unit cell changed. These changes are slight because the dielectric Keywords: Reflectarray antenna, Phase range, Reflected phase diagram, Losses.
