Hello

I have a matching network that has a source impedance of 4 ohms and a terminating impedance of 50 ohms.

The circuit is basically a filter.

I can do a single port S11 measurement of the circuit if I cal the VNA for 50 Z and just terminate the source with

a 4z load. I am trying to figure out how can I look at the response or shape of the filter so I can be sure that it

rolls off at the desired frequency. My problem is that while one port of my circuit is 50 Z the other is 4 Z so I am

unsure how to handle the 4 Z from the perspective of doing a one port 2port cal.

I am using a HP8753A with a HP778D Directional Coupler

Any suggestions most welcome

Thanks Paul

I have a matching network that has a source impedance of 4 ohms and a terminating impedance of 50 ohms.

The circuit is basically a filter.

I can do a single port S11 measurement of the circuit if I cal the VNA for 50 Z and just terminate the source with

a 4z load. I am trying to figure out how can I look at the response or shape of the filter so I can be sure that it

rolls off at the desired frequency. My problem is that while one port of my circuit is 50 Z the other is 4 Z so I am

unsure how to handle the 4 Z from the perspective of doing a one port 2port cal.

I am using a HP8753A with a HP778D Directional Coupler

Any suggestions most welcome

Thanks Paul

Alternatively, cal and measure in 50 ohms and download S2P file and look at things in a simulator.

More modern VNAs allow you to cal in 50 ohms then re-define a port impedance. That's the best way.