Calibration Standards and Phase Offset

There are two reasons why some types of reference standards show phaseshift after calibration:1. The reference plane of the standard is electrically offset from the mating plane of the test port. Such devices exhibit the properties of a small length of transmission line, and include a certain amount of phase shift. The amount of phase shift can be calculated with the formula:phi = (360 x f x l)/c8 meters/second)2. The standard is an open termination, which by definition exhibits a certain amount of fringe capacitance (and therefore phase shift). Open terminations which are offset from the mating plane will exhibit a phase shift due to the offset in addition to the phase shift caused by the fringe capacitance.The important point to remember is that these properties will not affect your measurements if the standards are properly defined in the analyzer. The analyzer compensates for them during measurement.