[SI-LIST] AW: Question about diff-probes
- From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- To: "Zaiyi Liao" <zaiyi.liao@xxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Tue, 5 Jan 2010 09:01:21 +0100
Hi Zaiyi,
Most of the handheld probes are built for oszilloscope usage only. There are
some very robust chip probes that can be positioned by hand without breaking
them at the first attempt (google: Z-Probes).
Another very nice and high bandwidth handhelt probe is available by Gigaprobes:
http://gigaprobes.com/ Unfortunately they do ot sell calibration substrates
that allow calibrating right at the tip of the probe, but you can get those
from a chip-probe vendor if needed.
Regarding your second question I think the main difference is speed or ease of
operation. The VNA gives you the S-Parameters (at least s2p) within seconds.
Going with round robin to get the differential s-parameters takes 6
measurements, which is a bit more time consuming. Multiport VNAs will give you
the differential data within seconds. Using TDR, you need 2 measurements for
s2p parameter calculation (TDR and TDT), which is done with one measurement
setup (just saving two different files). Using round robin thats 16
measurements. Then you need to do the post processing to get S-parameters from
the time domain data.
The accuracy should be the same for VNA and TDR as long as you are within the
dynamic range (which is much higher for VNAs).
Pricing might also be different. When we bought our equipment, the 4-Port VNA
was much more expensive than the 4-Port TDR Setup, but I don't know the current
pricing.
I hope this helps
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von Zaiyi Liao
Gesendet: Dienstag, 5. Januar 2010 04:46
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Question about diff-probes
Hello experts:
Now I want to test S-parameter of diff-channel on PCB.
I find it's hard to find portable low-impedance(50ohm) diff-probe for
VNA. As I know,there are some diff-probes up to 15Ghz (such as N1020A TDR
probe) for TDR test. And there are lot of high-impedance diff-probes for
eyepattern test up to 10Ghz. In chip test, there are many low-impedance
probes(GSG,GSGSG,GSSG,etc)
I want to know whether there is any portable(no need probe station)
diff-probe for VNA?? Why it's hard to find low-impedance probe for PCB test?
Another question is that what is the differences of S-parameter test by VNA and
TDR.
Thank you very much!
BR//Zaiyi Liao
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