Touchstone file types

Hello All,

I am wondering about the touchstone file types.

Is there any difference between saying DB MA or RI when referring to S-parameters(I know their difference, just a curiosity when saving s2p file through a VNA, shall I favor one over another in a specific situation)? I mostly used MA without a specific reason.

magnitude [dB] = 20 * Log(sqr(Re^2 + Im^2))

phase = arctan(Im / Re)

there are simple formulas to go from one type to another. So, I wonder what are they for?

Regards,

ktr

It's just a numerical resolution thing. If you have small dB values, the magnitude/angle or real/imag format in some files might not have enough digits resolution to represent small changes. But of course, that depends on how many decimal digits the software/device writes.

It's just that the new VNA we have in our company gives the choice between DB MA or RI and I realized, I never had much of a thought about them. Hence, I feared there may be a point I might miss. Currently I am measuring S11 and S22 of some amplifiers, so I don't think they matter much as of now; however I am curious about whether there is a rule of thumb about them(writer refers to DB MA or RI file formats here)

Generally, MA or DB is used in Transistor Data Sheet.

MA or DB is effective for grasping value's characteristics.

I prefer DB since DB/Angle is used for rectangular plot, although default of touchstone is "GHZ MA R 50".