Designing a multi-layer microstrip reflectarray with the use of an unit cell waveguide approach

In this paper, an equivalent unit cell waveguide approach (WGA) has been proposed to obtain reflection coefficient phase curves for a multi-layer microstrip reflectarray (MRA) with variable size patches. Based on this approach, a fast computer algorithm for generating reflection coefficient data has been developed and was validated against other methods described in the antenna literature. Following the verification of the validity of the WGA model, an offset feed two-layer printed MRA prototype with patches of variable size has been designed and developed for operation at 12.5 GHz. This antenna features a small scan angle of 20/spl deg/ has been thoroughly tested and has shown good performance. The achieved results for the unit cell and the array prove that the presented model and associated computer algorithm work properly. The developed tools should be useful in designing a multilayer MRA featuring a small scan angle for which reflection coefficient phase curves are approximately independent of direction of an incident plane wave.