Reconfigurable Antennas Based on Electrically Tunable Impedance Surfaces

We describe an electrically tunable impedance surface, and antennas based on such a surface. The structure is built as a periodic array of electrically small, coupled resonators, commonly known as a high-impedance surface. By tuning the resonance frequency of the surface as a function of position, one can generate an arbitrary refection phase that varies across the surface. This can be used to steer a reflected radio frequency beam, or to tune antennas that are placed near the surface. We describe such a surface that is electrically tunable using commercially available varactor diodes, and offer techniques for achieving full two-dimensional beam steering with a design that is optimized for bandwidth.