Electronic Beam Steering of an Active Metamaterial-Based Directive Subwavelength Cavity

In this paper, an active metamaterial based on microstrip technology is proposed for the design of a steerable ultra- compact directive cavity. This composite metamaterial acts as a Partially Reflective Surface (PRS). It is made of a constant inductive grid and an active capacitive grid by the insertion of varicap diodes. The metamaterial negative reflection phase combined with the phase at the surface of the substrate (very close to 180deg) above a conventional ground plane leads to the design of a subwavelength cavity. Furthermore, by changing the varactor bias voltage between the metallic strips of the capacitive grid of the PRS in one direction, the phases of the reflection and transmission coefficients vary. As a consequence, the resonance frequency of the antenna cavity and the steering of the radiated beam can be controlled electronically. The proposed cavity can provide a low-cost ultra-compact alternative to the traditional electrically scanned antennas.