Characteristic impedance of multilevel, multiconductor hybrid mode microstrip

Two definitions of modal characteristic impedance for multiconductor, hybrid-mode microstrip are compared. The sensitivity of each to numerical inaccuracies is discussed. The plausibility of negative values of modal characteristic impedance is shown for two-mode (three-line) asymmetric geometries, and numerical results are presented for dual-plane, asymmetric, coupled microstrip.<
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