Characteristic modal decomposition of reflection phase of a microstrip-patch reflectarray unit-cell

This paper introduces the use of characteristic mode theory to the design of reflectarrays. Specifically, the phase of the total reflected field is decomposed into the phases of modal reflected fields associated with the unit-cell of the reflectarray. It then becomes possible to shape the reflection phase curve of the unit-cell by suppressing the undesired modes, thereby improving bandwidth performance of the reflectarray.