Option 48 is an enhancement of, and exclusive of, Option 41 for noise figure discussed in Noise Figure (Option 41). Option 48 includes the ability to handle 3- and 4-port DUTs in a single-ended sense, differential and common mode noise figure for all DUTs with a variety of processing options, and the inclusion of a level of vector match correction to enhance accuracy. The menu system is augmented to help speed the calibration procedures. The measurement premise, that of cold source analysis, remains the same, as do most of the guiding principles on the receiver preamplifier/filtering discussed in Noise Figure (Option 41).

Much work has been published in the area of differential noise figure (e.g., [1]-[7]) although there is still some inconsistency on terminology and on measurement approaches. This chapter does not attempt to resolve these issues, but is instead intended to suggest one way forward that potentially has some practical advantages, is largely self-consistent, and can lead to some reasonable measurement results in a wide range of DUT configurations.