Scattered Reflections on Scattering Parameters — Demystifying Complex-Referenced S Parameters —


IEICE TRANSACTIONS on Electronics   Vol.E99-C    No.10    pp.1100-1112
Publication Date: 2016/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E99.C.1100
Type of Manuscript: Special Section INVITED PAPER (Special Section on Microwave and Millimeter-Wave Technology)
S parameters,  reflection coefficient,  transmission coefficient,  traveling waves,  pseudo waves,  power waves,  reference impedance,  renormalization transformation,  

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The most commonly used scattering parameters (S parameters) are normalized to a real reference resistance, typically 50Ω. In some cases, the use of S parameters normalized to some complex reference impedance is essential or convenient. But there are different definitions of complex-referenced S parameters that are incompatible with each other and serve different purposes. To make matters worse, different simulators implement different ones and which ones are implemented is rarely properly documented. What are possible scenarios in which using the right one matters? This tutorial-style paper is meant as an informal and not overly technical exposition of some such confusing aspects of S parameters, for those who have a basic familiarity with the ordinary, real-referenced S parameters.