The s parameters of a balun ( three port) are:

s12 = -s13 = s21 = -s31 and,

s11 = -infinity.

What does this mean in terms of conceptual understanding? The interpretation of these s parameter statements are:

1. A balun is a three port device with a matched input and differential outputs.
2. A balun is a three port power splitter
3. The two outputs from a  balun are equal in amplitude but opposite in phase.
4. The voltage of one balanced output is the negative of the other balanced output.
5. The input is matched to the input transmission line.
6. The usual impedance is 50 Ohms. But it could be something else.
7. A balun is a reciprocal device. Its output and inputs may be exchanged

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