This paper is focused on the control of the electrical characteristics of resonant type metamaterial transmission lines, that
is, transmission lines loaded with complementary split ring resonators (CSRRs). The key parameters of metamaterial
transmission lines for microwave and millimetre wave circuit design are the characteristic impedance and the phase
constant (rather than the effective magnetic permeability or dielectric permittivity). Thanks to the presence of reactive
elements loading the host line, metamaterial transmission lines exhibit a major design flexibility that can be useful for
circuit design purposes. Specifically, we can tailor the dispersion diagram and the characteristic impedance to some
extent. By virtue of this, it is possible the design of microwave and millimetre wave components with superior
performance in terms of bandwidth, or the design of multi-band components, both of interest in modern wireless
communication systems. Thanks to the small electrical size of the unit cell of such lines, the resulting metamaterial-based
components are also very small and fully compatible with planar technology (that is, no lumped elements are
used). Different examples are provided to illustrate the possibilities of resonant type metamaterial transmission lines.
This includes hybrid couplers, power dividers and phase shifters, among others. The paper includes also the theoretical
foundations of the approach.