Abstract
This paper presents geometrical-based wideband circuit models for different configurations of loaded slotline and loaded coplanar waveguide (CPW). It investigates, first, the strip-loaded slotline and then extends the developed model to strip and split-ring resonator (SRR)-loaded CPW. The proposed models successfully describe the behavior of several structures of interest in the literature and provide new insights on the design procedure. They operate over the entire frequency range if higher order modes are not generated without the need for fitting parameters. This paper also presents three applications, of which the design relies on the proposed modeling methodology. They are a third order maximally flat low-pass filter with 1.4-GHz cutoff frequency, a 3-GHz slow wave structure with a slow wave factor larger than 2 in the linear range of the dispersion relation, and a balanced composite right-/left-handed SRR-loaded CPW with 100% (2.31-7.1 GHz) fractional bandwidth. Experimental results, which are in a very good agreement with the electromagnetic simulations, confirm the proposed theory.