Istvan,
If the trace impedance is off by much more than 5% and the launch signal
integrity is bad (peak TDR impedances of >10ohms), you would have a long
resonator essentially, that could also cause the half wave resonances also I
believe. Would you agree?
- Al
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On May 23, 2016, at 4:40 AM, Istvan Novak <istvan.novak@xxxxxxxxxxx> wrote:
John,
Becasuse of the matrix inversions involved, deembedding can be very
sensitive to minor measurement errors and inaccuracies. You may see
those spikes near multiples of half wavelength frequencies of the
structure where the main diagonal elements of the S matrices go through
zeros.
Regards,
Istvan Novak
Oracle
On 5/23/2016 12:00 AM, John Lin wrote:
Dear all SI gurus,------------------------------------------------------------------
While doing de-embedding by removing 5 inch trace as fixture from 16
inch trace,
I find there are many spikes on my de-embedded S21 plot.
Here are my approaches.
1. Transfer both 5 inch and 16 inch S2P file to T paramter (matrix)
2. cut the 5inch into half by T_2p5inch *T_2p5inch = T_5inch ==>
T_2p5inch=T_5inch^ 0.5; assuming symmetry.
3. do inverse(T_2p5inch)
4. De-embedded result = inv(T_2p5inch)*T_16inch*inv(T_2p5inch)
5. Convert De-embedded T parameters back to S parameters.
I also use Delta-L for de-embedding. Both S21 plot can match well,
except the spikes.
I don't know what happen for the spikes and seek any idea from you.
Thanks,
John Lin
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