But renormalization just changes the calculation for the S parameters.
It doesn't fix the change in Q.
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-----Original Message-----
From: <
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Sent: Feb 14, 2025 4:20 PM
To: <
[email protected]>
Subject: Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
Jim,
Of course the change in termination impedance changes the filter response. The point of the renormalization is that the response can be recalculated to show what it would be at the different impedance. Doing so requires knowledge of the transfer function and the impedance of both ports.
Similar case: If you know the open circuit voltage and output impedance of a source, you can compute its output level into any impedance.
--John
On Fri, Feb 14, 2025 at 09:42 AM, Jim Lux wrote:
Since most filters are a series of resonators of some kind or another,
terminating them in a resistance other than the design resistance will
probably change the filter characteristics. Consider a filter that effectively
has an input that is a RLC circuit, where the R is the terminating impedance
of the source. If you change R from, say, 300 ohms to 50 ohms, then the Q
will be different. That will certainly change the skirts, and will also
probably change the overall passband (since most filters are stacked up
responses of multiple resonances).
