Tunable metamaterials

The realisation of Cognitive Radio systems will involve producing antenna and microwave components that can be reconfigured for different parts of the frequency spectrum. Many antennas and related components operate at multiple frequency bands but further reconfigurabilty and miniaturisation will be necessary to meet Cognitive Radio specifications.

In this study we have investigated the tuning of electromagnetic band gap surfaces to be used as high impedance surfaces with multiband antennas.

The research has examined dual frequency band tunable EBGs using both single and dual layer structures. The frequency bands must be independently tunable.

The surface below is part of a dual layer EBG based on square patch elements with varactor diodes inserted to give a variable frequency response. The surface was tunable from about 700 to 1200 MHz and 1700 to 2800 MHz. Further work resulted in a single layer surface with a similar performance.

Tunable EBG

Upper frequency band tuning range