Criteria for the evaluation of linear two-port stability using two geometrically derived parameters

Chin-Chun Meng*, Hung Ju Wei, Po Hsing Sun

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Two geometrically derived stability parameters,μ' (or μ) and ν' (orν ), are used to analyze the stability of a two-port network. The magnitudes of both μ' (or μ ) and ν'(or ν) parameters determine geometrical relations between the stability circle and the unit Smith chart in the ⌈S (or ⌈L) plane. |μ'| (or |μ|) is defined as the minimum distance from the stability circle to the origin of the unit Smith chart in the ⌈S (or ⌈L) plane, while |ν'|(or |ν|) is defined as the maximum distance. Moreover, the signs of ν'(or ν) and μ'(orμ ) parameters determine which region of the stability circle is stable (inside or outside) and whether the stable region includes the origin of the Smith chart, respectively. There are totally 12 situations between the stability circle and the unit Smith chart in the ⌈S (or ⌈L) plane by using μ' (or μ) and (orν ) parameters. This paper classifies 12 situations in the ⌈S plane and also presents the corresponding practical two-port networks.

Original languageEnglish
Pages (from-to)65-72
Number of pages8
JournalInternational Journal of Microwave and Wireless Technologies
Issue number1
StatePublished - 1 Feb 2009


  • Linear circuit
  • S parameters
  • Stability criteria
  • Two-port network

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