00826833IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 48, NO. 3, MARCH 2000 347 Accurate Circuit Model of Interdigital Capacitor and Its Application to Design of New Quasi-Lumped Miniaturized Filters with Suppression of Harmonic Resonance Lei Zhu, Member, IEEE, and Ke Wu, Senior Member, IEEE Abstract―A general-purpose circuit model of microstrip interdigital capacitor (IDC) is presented in this paper for use in the design of new quasi-lumped miniaturized filters. This computeraided-design-oriented model is developed as a versatile admittance -network with the short-open calibration technique that we have recently proposed for accurate parameter extraction of a circuit from its physical layout. This technique is self-contained in our method of moments, which accounts for frequency di……