[SI-LIST] Re: Resonance in traces?
- From: Andrew Ingraham <a.ingraham@xxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Sun, 11 Mar 2012 21:30:12 -0400
Aaditya Kandibanda wrote:
> I was wondering about the quarter
> wavelength and half wavelength concepts, can you emphasize some more
> information on it please?
For an unterminated trace or cable or transmission line with an "open"
on the far end, in the vicinity of the frequency where it is a quarter
wavelength long or an odd multiple of a quarter wavelength long, the
line behaves (as seen from the source end) about the same as a high-Q,
series resonance.
In the vicinity of frequencies where it is a half wavelength long or
whole multiples of it, it looks like parallel resonance.
It is by nature of it being a finite length transmission line without
anything there to dissipate the energy, so standing waves form which
makes the feedpoint impedance very low, or very high. Coupling with
other traces does not cause it, but coupling could modify slightly the
resonant frequencies from what they would be without coupling. By
examining those standing waves, you can determine what the signal
looks like on the trace.
Is this what you want, or do you need more detail than that?
Andy
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