I need S Parameters

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I need S Parameters

Post by Sam » Thu Dec 09, 2010 12:29 am

For testing purposes, I need to obtain S-parameters for filters. Any reasonably selective filter, but an MCF style would be great. It would also be best if the filter is not matched to 50 ohms. The ideal filter would be an RBW-style filter. If anyone has such parameters, please email them to me.

I can use a full two-port set of parameters, or separate S11 and S21 scans.

A quick update on the software will explain what I am doing. The current release gathers a single set of reflection or transmission parameters at a time. It also graphs them as separate parameters.

The current non-released version has a new Two-Port Module. This will ultimately have many uses, but currently it allows for assembling a set of two-port parameters by retrieving them from the scan data or loading files. For example you load "S11" into S11 and S22, and "S21" into S21 and S12, an approach that would be reasonably accurate for filters.

Once you have the full two-port assembled, you can do certain calculations, such as transforming to a different reference impedance, or calculating impedance matches. Impedance matching is not simply a matter of doing a conjugate match to S11 and S22, because the actual input reflection depends on the output terminating impedance, and vice versa. So once you conjugately match the input and output, the thing you are conjugately matching changes. I'm trying to develop an automated method to find the proper match.

I could create a filter in RFSim99 and generate S-parameters, but I would prefer to use a real-world filter.

This Two-Port module is the first step in enabling the MSA to collect transmission and reflection data with a single command, and even to reverse the DUT direction and collect the full two-port parameters. I have also done considerable work on that, but that is not the immediate concern.

Sam W.

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