Comprehensive Study of the Spurious Effects on the Signal Guidance in Coplanar Waveguides

A study of the propagation characteristics and several signal integrity aspects of a conventional coplanar waveguide (CPW) is presented here. The study considers the bound and leaky modes supported by this structure up to high frequencies. The analysis of the dispersion characteristics of the structure is complemented with the study of the voltage excited along the line when fed by a delta-gap source of current. The results thus obtained allow us to discuss on the physical meaning of the modes and the relevance of the residual wave, which is key to link the practical role played by the different modal solutions with the spurious effects that may appear in the structure. The analysis of the eye-diagram performance also reveals that the signal integrity in CPW systems basically relies on the excitation of the parasitic fundamental coupled slotline mode as well as the high-frequency excitation of the continuous spectrum. These aspects have been studied in detail.