[SI-LIST] Re: TDR vs. VNA? Which to purchase?
- From: "Lars Juul" <write2larsj@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 19 Feb 2008 16:21:48 +0100
Hi Tom.
For characterization and validation of new board designs, I'd personally go
for the TDR, as the hunt for discontinuities and other impedance mismatches
on a board is far more easy in the time domain. I believe some models also
show the excess capacitance/inductance.
But again, there are exceptions, depending on the interface you want to
characterize. Take the XFP interface for instance. It has some of the
electrical interconnect parameters defined in terms of DS11, DS21. If you
want to demonstrate compliance you really do need a VNA to measure it.
For video applications, I'm not sure what the requirements are, but I doubt
a VNA is the answer to your questions, unless RF is involved.
Hope this helps.
Lars
2008/2/19, Tom Cipollone <tom_cip_11551@xxxxxxxxx>:
>
> Hi,
>
> I realize that this thread has been done before, but as we all know,
> technology changes pretty fast, and what might have been true a year or two
> ago, may not still be true today.
>
> I am ready to make a large investment in signal integrity test equipment
> for my company. I'm probably no more than a week away from the decision. As
> some of you will no doubt suggest to get both, let me just say that I can
> not afford both. I will have one or the other.
>
> I have had the demos and seen the equipment.
>
> What I do for a living is design boards for digital video, that are
> comprised of many differential pairs, routed closely together. Rising edges
> are in the neighborhood of 100 ps. I want to be able to find and modify
> discontinuities (either capacitive or inductive), determine crosstalk
> between the pairs and measusre jitter (yes, I will need a signal source for
> that).
>
> If this were as little as two years ago I would have believed that the
> VNA solution would have been the most versatile. However, Tektronix has made
> a lot of progress with their TDR equipment and with their "Iconnect"
> software. Also, there is a big difference in price between the TDR solution
> and the VNA solution.
>
> In appealing to the SI group for opinions I am trying to go beyond my
> own predjudice and the marketing hype.
>
> Thank You
> Tom
>
>
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