Various TEM transmission line structures have been proposed in the literature, and their electrical parameters have been computed in many cases with reference to simplified models. These models have been already validated for more conventional structures, and were expected to lead again to good results. Some comparison with accurate general purpose computation procedures are presented, using numerical inversion of the Schwarz-Christoffel formula, and successive over-relaxation procedures on transformed geometries in case of an inhomogeneous dielectric.

Inhomogeneous dielectric transmission line geometries analysed by combining conformal mapping-finite difference procedures

Due to features useful in microwave and millimeter wave integrated circuit design, unconventional planar transmission line geometries deserve large attention in the present technical literature. In particular, V-shaped and elliptic or circular-shaped microshield lines have been analysed in previous works. In this paper, accurate conformal mapping procedures are used to compare and to complete previous results on quasi TEM propagation characteristics, and to investigate useful coupled-line geometries.

http://ieeexplore.ieee.org/iel3/3556/10650/00498032.pdf

Conformal mapping analysis of microshield transmission lines

Conformal mapping analysis (of microshield transmission lines

On the magnetic-wall approximation for their slots, shielded coplanar waveguides (SCPWs) and semienclosed CPWs (SECPWs) are analyzed through an intensive use of elliptic function transformation. CAD-oriented formulas for the quasi-TEM parameters of SCPWs and SECPWs, including their coupled versions, are derived. The comparison of the results calculated here with previous ones show 2% accuracy for formulas in the practical situation where the slots are not too wide, e.g., s / (s + 2w) ≥ 0.2 for an SCPW. © 1994 John Wiley & Sons, Inc.

Changhua Wan

Papers

CAD-oriented formulas for the quasi-tem parameters of shielded and semi-enclosed (coupled) coplanar waveguides