A typical poorly designed SMA resonates for >100psec, and since 1 of
microstrip prop delay is around 150psec your going to run into trouble. Since
your fixture probably goes single ended then coplanar coupled my guess is you
have a significant impedance bump on the coupling region also. Our platform
SE to coupled DIFF is not trivial to design and was a challenge.
We do not de-embed when doing crosstalk analysis like ICR, ICN, PEXT, etc.,
for compliance.
- Al
Products for the Signal Integrity Practitioner
Alfred P. Neves
Chief Technologist
Office: 503-679-2429
www.wildrivertech.com
On May 5, 2015, at 3:55 AM, Istvan Novak <istvan.novak@xxxxxxxxxxx> wrote:
An 0.6-inch long trace is very challenging to measure...
Regards,
Istvan Novak
Oracle
On 5/5/2015 3:11 AM, jun zhang wrote:
Hi experts,
I have designed a PCB test coupon to measure the impedance curve and
crosstalk curve from 0-10GHz.
My test trace is about 0.6". At each end of the trace, there is a co-planar
trace about 1" connected to SMA connector. Therefore the total length of
the coupon is about 2.6".
I have some question below:
1. When testing TDR, do you think 0.6" is too short to be displayed? If the
characteristic can be displayed, I think I need not to de-embed the
influences of the co-planar traces at both ends. Am I right?
2. When testing TDR, I have two ways. The first is using TDR instrument to
measure it directly; the second way is tranforming SDD11 obtained by VNA to
time domain.The second way is more convinient for me. Which method is more
suitable for displaying the impedance for the 0.6" test trace? .
3.When testing crosstalk, I will de-embed the co-planar trace to reveal
only the characteristic of the test trace. I plan to do de-embedding by ISD
offered by AtaiTec Co. My concern is still that whether this method can
give me accrate de-embedding result in the case that my test trace is only
0.6" long. I think if the trace is longer, maybe the influence of
multi-reflection from co-planar trace will be minor because of the loss of
the trace. Under this consideration, I think the longer the test trace
length is, the better accurate de-embedding results we can obtain. Am I
right?
Hope to your reply
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