Equivalent Circuit Model Development Accounting for Mutual-Coupling Effects

Mutual-coupling effects are of utmost importance in the development of high-frequency circuits and systems. However, it is a common practice to ignore those couplings when establishing equivalent circuit models. Neglecting these couplings leads to inaccurate circuit modelling. Therefore, it becomes imperative to account for mutual couplings in the development of accurate equivalent circuit models. This work presents a holistic process for synthesizing the equivalent circuit model of an electromagnetic (EM) field structure that incorporates mutual couplings of varying orders. The proposed high-order framework begins by developing equivalent circuit models for each individual transmission line discontinuity within the target circuit. Subsequently, the mutual couplings of different orders are extracted in a step-by-step manner. Throughout this process, full-wave EM simulations are deployed, along with a circuit parameter extraction method that utilizes de-embedded circuit responses. By combining these techniques, a comprehensive and accurate equivalent circuit model is generated, enabling a detailed analysis of the target field model structure, and facilitating a deeper understanding of its electrical and magnetic behavior and performance. This paper utilizes a three-step microstrip discontinuity structure and a third-order parallel coupled microstrip filter as examples for theoretical and experimental demonstration of the proposed technique.