Network analyzer output

[giangriff88]

Hallo everyone,

I was wondering how the S parameters are measured.
In particular, if I attach the network analyzer to a variable resistor which varies over frequency let´s say from 50 to 5 Ohm, will I have constant output power at the output of the network analyzer? What I am interested in understanding is what will the voltage drop on the resistor be, and if I can assume it to be constant or not.

Thank you very much

 

[ge]

Very gray area giangriff88. When measuring the output "power" of a VNA with a power meter, you will get a reasonably constant output across a good 50ohm load. For non-50 ohm loads, your voltage drop across your resistor proportional to the reflected energy. Review a VSWR/Return Loss table.

 

[volker@muehlhaus]

Agreed. And because S-parameter measurement is a measurement of ratios of incident and transmitted or reflected wave, there is no technical requirement for constant incident power.

 

[Raghav Kapur]

There are a couple of good white papers that can help you

1. Fundamentals of Vector Network Analysis - Primer from Rohde & Schwars: https://www.everythingrf.com/whitepapers/details/447-fundamentals-of-vector-network-analysis-primer

2. Understanding Vector Network Analysis from Anritsu - https://www.everythingrf.com/whitepapers/details/375-understanding-vector-network-analysis

You can also find more white papers on Network Analyzers here - https://www.everythingrf.com/whitepapers/search/?q=network%20analyzer