Polarization Analysis of Reflectarray Unit Elements Using Characteristic Modes

Polarization analysis for reflection waves from a circularly polarized (CP) reflectarray unit element is studied in detail in this work. Characteristic mode analysis is adopted to analyze the wave excitation and reflection waves. It's found that the polarization of the reflected waves depends on the polarization of the incident waves, and a CP reflection wave or a linearly polarized (LP) reflection wave can be achieved with a properly oriented LP incident wave. Moreover, it is also found that when a CP wave is incident on a CP element, it has LP reflection waves at the CP frequency of the unit element.