Microstrip patches for a reflectarray

Microstrip patch element geometry is indeed an important factor in the design of a microstrip reflectarray. In essence, each of these perfectly conductive elements creates a minuscule correction to the reflection phase of the scattered field so that a phase coherent main beam is constructed. The geometrical dimensions of these elements must therefore be carefully designed as such. Three types of microstrip patch geometries considered in this analysis: a rectangular patch; a rectangular patch with a single stub; and a rectangular patch with twin stubs. These stub attachments are in fact phase delay transmission lines employed to fine-tune the reflection phase of the reflectarray so that a constant phase is achieved at a projected aperture plane in front of the reflectarray. On the other hand, a reflectarray using the first geometry utilizes the variation of patch lengths for reflection phase control. To design a microstrip reflectarray, a modelling approximation of the scattering from an infinite periodic array of microstrip patches is employed.