Hi Vadim,
Have you tried the de-embedding code available from the IEEE?
https://gitlab.com/IEEE-SA/ElecChar/P370
You only need a 2x thru and it accounts for impedance discontinuities.
If you need to shift the reference plane, the one provided by Amphenol can
do that.
https://www.amphenol-icc.com/software
Again you only need a 2x-thru.
Cheers,
Jason
On Fri, Apr 12, 2019, 2:45 AM heyfitch <dmarc-noreply@xxxxxxxxxxxxx> wrote:
Thank you, Istvan.
I used 1mm pitch probes because they had to be landed on BGA pads on a 1mm
grid but diagonally and BullsEye pads. I could probably do with 750um
instead and still catch gnd. I hoped there may be some calibration trick
that would artificially shift ref plane up the probe tip.
Vadim
On Apr 11, 2019, at 22:00, Istvan Novak (Redacted sender "istvan.novak"
for DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
Vadim,
If your observation is that the measured data correlates better when you
include some small (otherwise unexplained) series inductance in the
model, yes, this has been observed. We found that the value of this
extra inductance was smaller with smaller probe pitch, so you may want
to use the smallest probe that you can make the connection with.
Best regards,
Istvan Novak
Samtec
On 4/11/2019 10:16 PM, heyfitch (Redacted sender heyfitch for DMARC)wrote:
Hello Experts -substrate and calkit from the same vendor.
When calibrating VNA to probe tip, we typically use ceramic cal
After verifying the cal (on a Thru, for example), we proceed to domeasurements on PCB. A careful look at the data suggests that the reference
plane shifts from the probe tip into the PCB; the measurement does not
include the excessive inductance of the BGA pad/via that we know should be
there. We estimate that this âmissingâ inductance would be just what is
needed to offset the BGA ball capacitance, which we estimate to be about
0.2pF/ball.
it? Is there a way âto forceâ the reference plane to stay at the probe
Here are my questions:
Have you observed such a shift of reference plane? How do you deal with
tip?
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Vadim Heyfitch
Xilinx
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