A n analytical load model is derived for capacitive coupled on-chip interconnect buses. @an estimation of the wire length is available, the driver output can be estimated using the load model and take coupling effects on the interconnect tree into account. The load is modeledas a a-networkwhich depends on the j r s t three moments of the exact admittance function ofthe bus system. Simulations with spectres has shown, that the model represents a good approximation for the driver load of a distributed interconnect bus tree. It is proven mathematically that the model remains passive.

Abstract. Complex integrated systems contain more and more on-chip components which exchange data and access memories via buses. To consider parasitic effects on bus structures during the early design phase appropriate models and wiring methods must be available. A RC-Pi model is proposed to model the load of a bus driver cell that also considers capacitive coupling between the signal lines. On the basis of simple estimations it is shown under what conditions the influence of inductance on the bus is negligible. Furthermore a method to consider inductive effects is shown. An early consideration of parasitic effects on global interconnect structures and an assertion which effects have to be considered is mandatory to effectively estimate the behavior of wires. Hence it also helps to avoid wrong assumptions.

Zusammenfassung:In der industriellen Anwendung kapazitiver Sensoren ist die kontaktlose Detektion leitfähi-ger Schichten flüssiger Medien von Bedeutung. Dabei ist die Sensorimpedanz abhängig von der Frequenz und Eigenschaften des Mediums. Um den Einfluss dieser Parameter zu ermitteln, wurde ein zweidimensionales, rotationssymmetrisches Modell erstellt, mit dem sich eine gute Übereinstimmung mit einer FEM-Simulation erzielen lässt. Aus den durchgeführten Untersuchungen geht hervor, dass sich aus den Parametern eines geeigneten Ersatzschaltbildes ein Maẞ für Leitfähigkeit und Schichtdicke des Mediums ableiten lässt.Schlüsselwörter: Impedanzsensoren, kapazitive Sensoren, Schichtdetektion, analytische Modellierung, FEMModellierung.Abstract: In many industrial applications of capacitive sensors, it is important to detect layers of conductive fluids. The sensor impedance depends on the frequency and properties of the fluid. To determine the influence of these parameters, a two-dimensional, rotationally symmetric model with variable dimensions and material properties is derived. The analytical calculations correspond well with FEM simulations. The parameters of a suitable equivalent circuit can be utilized to approximate conductivity and layer thickness of the fluid.

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