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A theoretical justification is presented of the partial-capacitance (PC) approach, widely exploited in the modeling of coplanar waveguides on finite-thickness and multilayered substrates. The analysis is based on the static spectral-domain approach to the computation of the capacitance of a set of planar conductors embedded into a multilayered substrate. It is shown that the PC method can be derived from approximating the static Green's function of a multilayered dielectric as the sum of partial contributions; such a decomposition can be applied to the Green's function either in parallel (admittance) or series (impedance) form. The resulting (parallel or series) PC approaches are shown to be accurate with substrates having layers of decreasing or increasing permittivity, respectively. Lines backed by magnetic or electric walls are introduced as limiting cases of multilayered structures. [ABSTRACT FROM AUTHOR]

An efficient finite-element reduced-order quasi-TEM model for the frequency-dependent characteristics of lossy multiconductor transmission lines is presented. Conductor losses are evaluated as functions of frequency through a magneto-quasi-static model. Numerically generated problem-matched basis functions reduce the problem size and, therefore, the CPU time required by frequency sweeps without appreciable loss of accuracy. The proposed approach is applied to complex coplanar waveguides and to multiconductor interconnects; its results are compared with quasianalytical techniques and with the full-wave finite-element method. [ABSTRACT FROM AUTHOR]

Examines coplanar waveguides with arbitrary polygonal geometry using conformal mapping approach. Estimation of capacitance, inductance, impedance and skin-effect attenuation; Application in electrooptic modulators; Electrode geometry optimization; Comparison of conformal mapping with full-wave finite element method.

Focuses on microwave modeling and characterization of thick coplanar waveguides on oxide-coated lithium niobate substrates for electrooptical applications. Cross section of coplanar waveguide for electrooptic modulator applications; Extraction of the characteristics impedance.

The computer-aided design and optimization of Ge-on-Si pin waveguide photodetectors is usually performed by a multiphysics analysis, where carrier transport is described with the drift-diffusion model. This paper addresses the shortcomings of this approach when applied to the study of the n-on-p detector configuration, ascribes them to the overly simplified model of the Si/Ge heterojunction, and proposes an enhanced description of the interfacial region. Starting from technological considerations, a thin buffer layer is introduced between Si and Ge, with a graded composition profile that mimics the initial low-temperature epitaxial growth process and mitigates the sharp discontinuity of the abrupt Si/Ge heterojunction in the band diagram. The benefits of this more realistic model on the determination of the electrooptic response are demonstrated and discussed. [ABSTRACT FROM AUTHOR]