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Describing the stop bandwidth of a filter using S11 and S12 parameters

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snkhan

snkhan

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while considering the stop bandwidth of a filter one should describe in terms of S11 or S21.
 

Re: S11 Vs S21 @ Filters

It basically depends on the application. S21 provides the description of the filter, while S11 (matching) in the stop is upon the application specifications.
 

Re: S11 Vs S21 @ Filters

S21 provides the description of the filter
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So if i want to describe the bandwidth of a filter, should it be describe in term of S11 or S2
 

Re: S11 Vs S21 @ Filters

Both.
In an ideal two-port loss-free network |S11|^2=1-|S21|^2.
You must just check the band in which the |S11| is below a specified value
(e.g. |S11| < -26 dB).
That range of frequency is the passing band.
 

Re: S11 Vs S21 @ Filters

Filter bandwidth is defined by S21. To match filter in a circuit you should use a filter by low S11, (S11 ~ 0). I agree with Aleksej.
 

Re: S11 Vs S21 @ Filters

s11 characterizes the filter when looking at the input. s21 is a characterization of the through and insertion loss. To add more confusion, there are numerous definitions of bandwidth that are often applied. Decide which one you want.
 

Re: S11 Vs S21 @ Filters

I think the bandwidth be measured in S21 similar as group delay
 

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