We introduce a novel parameterization scheme based on the generalized method of characteristics (MoC) for macromodels of transmission-line structures having a cross section depending on several free geometrical and material parameters. This situation is common in early design stages, when the physical structures still have to be finalized and optimized under signal integrity and electromagnetic compatibility constraints. The topology of the adopted line macromodels has been demonstrated to guarantee excellent accuracy and efficiency. The key factors are propagation delay extraction and rational approximations, which intrinsically lead to a SPICE-compatible macromodel stamp. We introduce a scheme that parameterizes this stamp as a function of geometrical and material parameters such as conductor-width and separation, dielectric thickness, and permettivity. The parameterization is performed via multidimensional interpolation of the residue matrices in the rational approximation of characteristic admittance and propagation operators. A significant advantage of this approach consists of the possibility of efficiently utilizing the MoC methodology in an optimization scheme and eventually helping the design of interconnects. We apply the proposed scheme to flexible printed interconnects that are typically found in portable devices having moving parts. Several validations demonstrate the effectiveness of the approach.

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This paper presents a systematic procedure for optimizing the geometry of high-speed data links based on Signal Integrity constraints. The structures under consideration are flexible printed circuits typically found in mobile devices having moving parts. Since the geometry of such interconnects is approximately translation-invariant, we adopt multiconductor transmission line models, characterized by broadband frequencydependent per-unit-length parameters that implicitly account for losses and dispersion. Each interconnect is characterized by several geometrical and material parameters, which constitute the free variables for optimization of the link. Signal integrity constraints such as return loss, impedance, attenuation, or ultimately eye diagram opening are used as goals in a closed-loop optimization process. We employ an efficient model parameterization scheme based on the Generalized Method of Characteristics to reduce the number of RLGC computations and to convert the parameterized model into a SPICE-ready deck for transient simulation and eye diagram generation under realistic loading conditions. Several numerical results illustrate the feasibility of the approach.