? The first three columns are conversion tables for return loss,
reflection coefficient, and SWR.
? The last four columns are values for interactions of a small phasor X
with a large phasor (unity reference) expressed in dB related to reference.
The RF Measurement Chart can be used to determine the uncertainty due to
bridge/autotester VNA directivity. The “X dB Below Reference” column
represents the difference between the directivity and the measured reflection
(return loss). The “ref + X dB” and “ref – X dB” values are the algebraic sum
of the error signal and the measured reflected signal as their phase relationship
varies over 360°. Therefore, the peak-to-peak ripple (1 ± X) is the total
measurement uncertainty caused by the error signal.
For example, if a 30 dB return loss is measured with a 40 dB directivity