Experimental Design of Passive and Active Microstrip Reflectarrays

In contrast to the numerical techniques conventionally used to analyse and design microstrip reflectarrays, in this paper a fully experimental approach is proposed. The overall procedure relies on the possibility to estimate the reflection phase of the single reflectarray cell by measuring the scattering characteristics of a small set of identical elements. This method, valid only when the mutual coupling can be ignored, has been successfully applied to both active and passive microstrip reflectarrays. For the passive case, the phase of the field scattered by patches with different sizes has been experimentally retrieved. In a second assessment, the phase curve of a varactor loaded microstrip antenna has been characterised. To prove the effectiveness of the proposed technique the experimentally generated data have been used to design two small reflectarrays. The measured radiation patterns are presented and discussed.