Coef N (Curve-fit Coefficients) (Graph)
The last section in the Graph Results panel lists the curve-fit coefficients that are used to create the curve-fit line shown in the Graph trace.
The name of the coefficients depends on the type of trace (AM Amplitude Modulation - CW modulation using amplitude variation in proportion to the amplitude of the modulating signal. Usually taken as DSB-LC for commercial broadcast transmissions and DSB-SC for multiplexed systems./PM Coef N, AM/AM Coef N, etc.). The number following the coefficient name indicates which term in the polynomial the coefficient multiplies.
The curve-fit line is represented by the following equation:
f(x) = s * ( a0 + a1*x + a2*x2 + ... + an*xn )
where
x = stimulus voltage (Vpk)
s = scale factor (from GraphPolyScaleFactor in the Graph trace's Data Header)
See following table for f(x) and an.
|
AM/AM |
f(x) = response voltage (Vpk) an = AM/AM Coef n |
|
AM/PM |
f(x) = differential phase between stimulus and response (in degrees) an = AM/PM Coef n |
|
Gain Compression |
f(x) = gain from stimulus to response an = Gain Compression Coef n |
The polynomial coefficients can also be read from the GraphPoly Data Header of the Graph trace.
To export the curve-fit line, you can use the Copy to register button on the dialog to create a separate trace containing the curve-fit line. If you need more flexibility, you can use the CopyGraphPolynomial macro (which basically does the same thing as the button) as a starting point and modify as desired.
See Also
