In this article, resonant-type tunable metamaterial transmission lines with independent control over the electrical parameters of the line, that is, the electrical length and characteristic impedance, are presented for the first time. Tuning is achieved by loading a host microstrip line with varactor-loaded complementary split ring resonators (VLCSRRs) and varactor diodes. By locating the varactor diodes in series configuration with the line, outside the region occupied by the VLCSRRs, it is possible to control the characteristic impedance and the electrical length (phase shift), over a wide band. As an illustrative example, a tunable 35 Ω/90° line functional between 0.4 and 0.8 GHz (which represents more than 65% tuning range), is presented and applied to the design of a transmission line power divider. The device is small and it exhibits reasonable performance. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1966-1970, 2009 Published online in Wiley InterScience (www.interscience.wiley.com).
- Impedance inverter
- Tunable lines