An Active High-Impedance Surface for Low-Profile Tunable and Steerable Antennas

In this letter, an approach for designing a tunable and steerable antenna is presented. The antenna model is based on a wideband bow-tie radiating element mounted above an active artificial magnetic conductor (AMC). The AMC geometry consists of a frequency selective surface (FSS) printed on a thin grounded dielectric slab in which some chip-set varactor diodes are placed between the metallic elements and the backing plane through vias. The resulting antenna can be tuned over the S-Band by simply changing all varactor capacitances through an appropriate biasing voltage. Moreover, this structure can operate a beam scanning over each working frequency by applying an appropriate biasing voltage to the active elements of the AMC surface in accordance to leaky radiation principles. The low-profile active antenna is characterized by an overall thickness of 5.32 mm, which corresponds to approximately lambda/24 at the center of the operating band.