General Analysis of Coupled Nonuniform Transmission Lines Based on State Transition Matrix

This letter presents an equation-based solution for the analysis of coupled nonuniform transmission lines (CNUTLs) in the frequency domain. The proposed methodology, which is based on state-transition matrix, models the Telegrapher's equations in form of linear position varying (LPV) system. Solving these equations with the Peano-Baker series (PBSs) provides the sought for closed-form far-end/near-end voltages and currents in the CNUTLs. Unlike the previous methods, due to the unique advantages of PBSs, such as versatility, performing with low-order terms, and subsequently, the high convergence rate, the proposed method is very fast and reliable. In order to validate the method, two practical CNUTLs of relevance in electromagnetic compatibility applications, namely, lossy/lossless exponentially and linearly tapered microstrips, are analyzed. Simulation results show that the proposed method is very accurate and fast in comparison to traditional methods.