Lengths Much Greater than One Wavelength

If the length of the calibration standard is more than one wavelength, incorrect Eeff results might be seen. However, the S-parameters are still completely valid.

Em’s calculation of Eeff is based on phase length. If the calibration standard is, say, 365 degrees long, em first calculates Eeff based on a phase length of 5 degrees. However, if a non-physical result is seen, em increases the calculated phase length by 360 degrees at a time until physical (i.e., Eeff ≥ 1.0) results are obtained. This usually corrects the problem.

Thus, it takes a particularly long calibration standard before the Eeff calculation fails. When it does fail, it suddenly jumps down to a value just above 1.0. Z0 and the de-embedded S-parameter data still have full validity. This failure mode is rarely seen.