Behaviour Study of Low-Loss Slow-Wave Coplanar Transmission Lines for RFIC Applications

Slow wave coplanar transmission lines (S-CPW), based on conventional coplanar CPW transmission lines with a floating patterned ground plane, consisting in floatting strips below the line, are good candidates for the integration of distributed RF circuits for front-end modules. They offer high quality factors when compared to conventional coplanar transmission lines. In this paper, guidelines are carried out for the design of such transmission lines. Simulations are first compared to already published measurements thus validating the simulation method used throughout the paper. Next, considering a standard 0.35 µm CMOS process, a design guideline is drawn in order to determine the characteristic impedance, the phase velocity and the dielectric effective constant of the S-CPW transmission lines, along with the attenuation loss and the quality factor. The effects of the floating strips duty cycle, the floating strip width and the ground plane width are studied.