Multifunctional microwave devices based on metamaterial transmission lines

Design of microwave devices based on a combination of traditional right-handed transmission line sections with positive dispersion and metamaterial left-handed transmission line sections with negative dispersion is considered. Compared to homogeneous transmission lines, the use of cascaded line sections gives additional degrees of freedom for the design of microwave devices with enlarged functionality and unique performance. Artificial way of right- and left-handed transmission lines realization based on lumped-element equivalent cells helps to minimize the dimensions of microwave devices. For filters, a combination of cascaded right- and left-handed transmission lines can be applied advantageously, to control the position and the widths of the individual pass-bands and the parasitic response of higher harmonics. The design of tunable dual-band filters is discussed and experimental results are presented. The miniature tuneable directional coupler is also under consideration. Artificial right- and left-handed transmission line sections based on lumped-element ¿-cells are employed. In order to verify the theoretical prediction, a tuneable lumped-element rat-race ring has been designed and experimentally investigated. Semiconductor varactor diodes have been used as tuneable components.