FAQs from Rohde & Schwarz

How to use the User Def. Math functionality


Can you please give me a general description of the User Def. Math functionality in the ZVA/B/T


If you want to use User Def. Math on an active trace, you don't have to add an additional trace because you can directly use it on the active trace.

For example: trc1 = trc1^0.5

User Def. Math always works on the linear voltage level, i.e. it works on "U".

Example: If the network analyzer is to show S11 in dB, the analyzer calculates the following:

10*log (P/1mW) = 10*log(U²/R/1mW) = 20*log(U) - 10 log(R) - 10log(1mW)

If you now want U -> U/2 (this means trc1 = trc1/2) =>

20*log(U/2) - 10log(R) - 10log(1mW)=

20*log(U) - 10log(R) - 10log(1mW) - 20*log(2) = P - 6 dB

If you want to bisect the power =>

P (log)= 10log(U²/2 / 1mW)

With P->P/2 =>

10log [ 1/2 [U²/2) / 1mW ] = P - 10log(2) = P - 3 dB