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Jim, I had the same thoughts myself, and earlier today I decided not to pursue graphical matching any further. My first impulse for a design problem of any complexity is to implement an optimizer. I

At some point, too, it's addressing a pretty niche need (essentially lumped component multisection filters). I would think that most people today designing a multi section filter use some sort of tool

Don, this sound like high values for the constant-Q curves would be necessary. Is that right? I'm trying to avoid keyboard input, such as specifying Q for one of these curves. So far the only keyboard

When making a graphical multi-section matching network solution, the constant-Q curves guide your component choices, to avoid unnecessarily constraining the bandwidth. The idea is to have each

A phase vs frequency plot helps identify where the middle of the transition is. Sometimes that's easier than trying to find the -3dB points. A classic S curve from +90 to -90 degrees phase, and 0 is

Thanks for all the details, Alan. My program does have group delay, which is differential phase shift. It does extract Q from S11 or S21 when measuring inductance. I've changed to displaying SWR

The rectangular plot of the one port S data is insufficient to determine Q. You will need the differential phase shift of the reflection coefficient as well. Taken together with the appropriate

Thanks for reminding me, Jim. I've been meaning to look into log scales, both x and y. Right now everything is linear only. Brian

OK, I see you calculated Q from the marker frequency values. Interpolation would be easy and would improve accuracy. Maybe I could add interpolated Q calculation to the marker. Looks like I would need

There's lots of different ways to plot the same data, and people develop their approaches based on the ones they're familiar with. I guess, too, in the "bad old days" when plots were done by hand (or

Thanks for the illustration. How did you get Q = 145.8? Why does the rectangular plot needs phase slope added to discern? Is the dip it too broad and shallow? A rectangular phase plot is available.

Here is an illustration... attached.

This is true for some measurements but not all... Consider a one port measurement, only S11, for a shunt series resonator.

The jig is made using one section of the commercially available NanoVNA test board. Available on eBay, Amazon and from Chinese sellers. You can find discussions about this board on several posts in

Alan, I don't understand what you're suggesting. If I wanted to find center frequency and Q, I'd just look at the rectangular plot, which is available. Brian

Thank you.

A useful addition to your bag is a constant Q contour. The Q = 1 contour permits resonator unloaded Q to be determined from S11 or S21 data overlaid on the chart. Three dB bandwidth and center

Hi Roger Apologies for resurrecting an old post I was just wondering if you could provide any details on the S11 / S21 test jig, it looks pretty much ideal for the matching tests I would like to try.

Nizar, The renormalization makes some assumptions that may not apply to your balun, in particular that S11=S22. This is often close to true for things like ceramic filters, but is probably not close

More Smith chart tricks: https://k6sti.neocities.org/splot.htm Brian