[SI-LIST] Re: 2 questions about TRL cal

Luciano,
How about other lines?
Thanks.

Mick

On Mon, Aug 8, 2011 at 10:52 AM, Luciano Boglione <l.boglione@xxxxxxxx>wrote:

> Mick,
>
> When you enter the delay, the reference planes are set at the edges of the
> delay line (i.e. at the probe tips); if you enter a 0 delay, the reference
> planes are set at length/2 of the delay line (mid point).
>
> Take care,
> Luciano
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Jim Nadolny
> Sent: Monday, August 08, 2011 10:45 AM
> To: Mick zhou; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: 2 questions about TRL cal
>
> Hey Mick -
>
> My 2 cents...
>
> On the delays - I always measure the delay differences in the line
> standards
> first, then specify the delays in the cal kit definition.  The result has
> been pretty good success with the behavior of the extracted models.  4 or 5
> years ago I was starting to dig into all this and was told (by an industry
> colleague) that the Agilent code does not use the delay numbers...so just
> use 0 ps.  When I asked Agilent about that practice they sort of looked at
> me like I had 3 heads - yes you need to specify the delay so that is what I
> do.  To be honest - I can't really answer your question though, just my
> experience.
>
> On the overlap - I use the overlap as a safety measure to cover variations
> in substrate performance.  Gives me margin when dealing with batch to batch
> variations in FR-406.  Having the overlap also allows you a range of
> frequencies that you can use to intelligently select as a transition
> frequency.  The selection of the transition frequency can impact the
> "steps"
> in the measured RL that is characteristic of TRL/M calibration.
>
> jn
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Mick zhou
> Sent: Monday, August 08, 2011 10:19 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] 2 questions about TRL cal
>
> All,
> There are two simple questions about TRL calibration that papers/app notes
> are not very clear about.
>
> 1. Is it necessary to enter delays of lines?
>    The entries are available in the GUI. I have seen people think the
> delays are not necessary and use 0ps for all. The argument is: the delay is
> determined as part of the process.  According to the theory, S12 and
> exp(-gamma*l) are determined to a sign ambiguity. Extra infomation such as
> delay is needed to uniquely decide the sign (therefore the phase).
>  However,
> delay may not be a problem for engineers who don't care phases. because
> they
> don't "see" the difference by looking at magnitudes only.  But this could
> be
> dangerous if the models without correct phases are used in time domain
> simulations, the delays could be wrong unless you are lucky the phases are
> always within 20-160 degrees (8:1 case).
>
> 2. Is overlap of frequencies necessary in case of multi-lines? Again it is
> related to accuracy of phases. Some believe overlaps can improve phase
> accuracy. Some don't believe so. The instrument picks up either the last
> (unguided cal) or the prority set by Smartcal (guided cal). So how the
> phase
> accuracy is improved?
>
> Thanks
>
> Mick
>
>
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