In this paper, a novel technique for constructing a design-oriented multi-layer coplanar waveguide (CPW) transmission line model is proposed. The technique uses a novel method to determine the conductive losses of an arbitrary CPW line, based on the losses of a limited set of measured reference lines, with a constant ground-to-ground spacing and a closed-form formula derived for standard CPW lines, to predict the geometric dependancy of the conductive losses. The characteristic impedance and effective dielectric constant are easily and accurately predicted using a quasi-TEM program. The final model contains a look-up table for Z_c and ε_eff and closed-form expressions for the losses. It can be easily implemented in commercial design software, and provides the designer with an accurate multi-layer CPW transmission line model which is fully scalable in strip- width, slot and length. The method has been verified by 3-D simulations and measurements of CPW lines on thin-film multi-layer MCM-D with very good accuracy. It is shown that the performance of the loss-scaling method is superior to the results obtained by 3-D simulations or by implementing conventional CAD formulas.
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