Electrically Controllable Artificial Transmission Line Transformer for Matching Purposes

In this paper, we present the application of a tunable artificial line as an impedance matching element. It is based on the transmission line approach of metamaterials and features separate control over line impedance and propagation constant. We show the useful exploitation of the special properties of a fully tunable composite right/left-handed line used as a transmission line transformer, which explicitly includes the use of the bandgap region. Corresponding transmission line theory illustrating the benefit of an artificial line is given. Measurements of a built device operating at 5 GHz and based on semiconductor varactor diodes are presented and compared to simulated results. A procedure to obtain the matchable impedance region from the measured scattering parameters is outlined and applied to measured and simulated data.