What is the cross-pol accuracy that can be achieved using a standard OEWG probe?
The OEWG has a typical cross-polarization along the two principal planes of -40 dB. If well made, it may be lower than this, but this is typical. If the OEWG is not calibrated and the analytical pattern is used in the processing, it assumes that the probe has no cross-pol. So the estimated error to signal ratio for measuring a -35 dB AUT is -5 dB. Converting this to an uncertainty in dB, gives an estimated uncertainty of 4 dB. If a lower error is required this can be achieved in two ways. If the probe is known to have a much lower cross pol level from previous measurements on this type of probe or if the manufacturer specifies a much lower level such as -60 dB, the estimated uncertainty reduces to about 1 dB. It is difficult to have high confidence in such a low cross-pol unless it is actually measured. The other way to reduce the final uncertainty is to calibrate the probe. In general, the way to reduce the AUT cross-pol uncertainty is to use a probe with the lowest cross-pol or to ca
