Modeling of transmission lines and passive elements for multilayer circuits

Monolithic microwave integrated circuits (MMICs) include a great variety of transmission-line structures and passive components in microstrip and coplanar technique. The small dimensions of CPWs require consideration of finite conductivity and electrode thickness. Moreover, the trend for miniaturization of the elements has excited vivid research in the areas of micromachined and microelectromechanical structures. Here real three-dimensional elements with complex cross-sections including very thin-even movable-layers have been developed, For the numerical description of these structures efficient CAD tools have to be provided, which are able to consider all these above mentioned features. Very soon most of them come up against limiting factors when they meet real complex structures and circuits. However, the limits, determined by the available computer memory and calculation time, can be extended by using adequate models for the analysis. Some of the numerical methods are described here with consideration of their efficiency and accuracy, based on the analysis of coplanar elements.