Two Port Rollett Stability Calculator
Calculate the Rollett K factor and determinant magnitude from complex two-port S parameters.
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Result
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Calculation steps
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How to calculate
Use all four complex S parameters at one common reference impedance, frequency and bias point.
Δ=S11S22−S12S21; K=(1−|S11|²−|S22|²+|Δ|²)/(2|S12S21|)
Worked example
S11=.2,S12=.05,S21=2,S22=.3 give delta−.04 and K4.358.
Assumptions and input details
Nonzero S12S21 required for finite K. K>1 and |delta|<1 are the classical small-signal two-port test; they do not establish broadband, nonlinear, internal-mode or practical hardware stability.
References: Keysight: Rollett expression
Using this calculator
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Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
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