Reading the S-Parameter Matrix and VNA Screens

Question I started with

I relabeled S11, S21, S31, and S23 by excitation and observation ports rather than treating them as curve names.

Reading the S-Parameter Matrix and VNA Screens — concept flow — I redrew the relationships before returning to the equations.

Connecting the concepts

For Sij, index j is the excited port and i is the observed response. Other ports are terminated in the reference impedance, and the matrix separates match, forward/reverse transmission, and isolation.

S11
S21
S31
isolation
VNA

Equations and assumptions

I write the reference impedance, units, and linear-versus-decibel domain before substituting numbers.

b = S aS21 = b2 / a1 when all other incident waves are zero

Worked example

Each output of an ideal equal power divider is 3.0103 dB below the input, so |S21|=|S31|≈0.707 and 20log10(0.707)≈−3.01 dB.

Reading the S-Parameter Matrix and VNA Screens — calculation relationship — This is my explanatory redraw, not an imported RFDH figure or a measurement result.

Connecting it to my coursework and projects

In my stored Cadence Wilkinson view I read S21/S31 split with S23 isolation. The branch-line amplitude curves alone do not prove 90-degree phase balance.

High-frequency engineering course hub

What I will check next

A simulation port is not automatically a calibrated VNA port. Without fixture de-embedding and reference-plane control, a plot is not described as a DUT-terminal measurement.

Pages I read

Official references I checked

Keysight: Understanding the Fundamental Principles of Vector Network Analysis