Dispersion analysis of capacitive loaded negative-refractive-index transmission lines and associated applications

Metamaterial or left-handed lines are synthesized by adding a series capacitance and a shunt inductance as loading elements to the host transmission lines. In this paper, we present analysis and design of a left-handed metamaterial line which is loaded with an extra shunt capacitor. Traditional metamaterial lines exhibit an inherent high-pass backward-wave response in their lowest harmonics. The additional shunt loading gives a tighter control on the band-pass response of the periodic structure. Moreover, shunt varactors can be used to tune the frequency response in the desired range. Dispersion properties of the structure are studied and design equations are presented for a generalized capacitive loaded left-handed transmission line structure. A practical compact tunable Wilkinson power divider based on the proposed structure is synthesized and simulation and experimental results are shown.