A symmetric coupled line equivalent circuit model for asymmetric coupled lines

Abstract

A new equivalent circuit model is proposed for an asymmetric coupled line based on a symmetric coupled line. The proposed equivalent circuit consists of a symmetric coupled line and two ideal transformers to represent an asymmetric coupled line and can be easily incorporated into the existing microwave and RF circuit simulators. This makes it easier to model and simulate the asymmetric coupled line circuits in terms of simple symmetric coupled lines. Using the proposed equivalent circuit model, it is shown that an asymmetric coupled line coupler is electrically equivalent to a symmetric coupled line coupler with transformed port impedances and the relation between the two couplers is investigated through the established equivalence. The validity of the proposed model is confirmed through the analysis of the directional couplers and the impedance transformers involving the asymmetric coupled lines. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:277–282, 2016.