HP 8753E User Manual page 666

Transmission Magnitude Uncertainty (Etm)
An analysis of the error model, located at the end of this appendix, yields an equation for
the transmission magnitude uncertainty. The equation contains all of the first order terms
and some of the significant second order terms. The terms under the radical are random in
character and are combined on an RSS basis. The terms in the systematic error group are
combined on a worst case basis. In all cases, the error terms are treated as linear absolute
magnitudes.
Transmission magnitude uncertainty (forward direction) = Etm =
Systematic = Efc + (Eft + EfsSll + EflS22 + EfsEflSBlSl2 + Ab2) S21
where
Efnt = effective noise on trace
Efnf = effective noise floor
Crtl = connector repeatability (transmission)
Ctml = cable 1 transmission magnitude stability
Dmsl = drift magnitudePC source to port
Efs = effective source match error
Eft = effective transmission tracking error
Efl = effective load match error
Efc = effective crosstalk error
The detailed equation for each of the above terms is derived from the signal flow model,
located at the end of this appendix.
Random = &Ct)2 + (Rt)2 + (Nt)2
Nt = -\/(EfntS21)2 + Efnf2
Drift and Stability = Dm2b2 S21
Determining System Measurement Unseertsinties