Adjustable High Impedance Surface for Active Reflectarray Applications

In this paper, the latest developments concerning the design of a centred reflectarray antenna based on a controllable (HIS) using varactor diodes are presented. The variable capacitance of these diodes allows the control of the reflection phase coefficient on all parts of the HIS. This property gives then almost full flexibility to shape the radiation pattern in the desired manner without modifying the structure of the antenna. After the presentation of some passive reflecting structures, the design of a new kind of adjustable elementary cell for active reflectarrays less sensitive to the non perfect properties of the varactors diodes is presented. Simulations have demonstrated the capabilities of active reflectarrays based on this new cell to focalise or scan the beam. A reduced size breadboard has also been manufactured to verify by experiments these capabilities.