[SI-LIST] Re: spatial resolution and effective rise time of VNA with TDR time-domain option
- From: "D G" <dgun@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 06 Nov 2002 00:25:03 +0800
The higher the bandwidth of the VNA, the faster the rise time of the step mode,
or the narrower the pulse for impulse mode. However, 110GHz for FR4
measurements is probably not realistic, since your high-frequency losses will
limit the available bandwidth.
On the other hand, it is very useful for low-loss DUTs (fault location, tuning,
reducing discontinuities) if you can afford the bandwidth.
- Daniel
From: "Daniel, Erik S., Ph.D." <Daniel.Erik@xxxxxxxx>
>
> All-
>
> According to the HP8510C manual, the effective risetime achievable in low
> pass time step mode is as follows:
>
> rise time = (1/fmax)*0.45 * F
>
> Where fmax is the max frequency, and F is a windowing factor =1.0 for the
> "minimum" window (which produces a step with some noticeable ring), F=2.2
> for the "normal" window (which seems to get rid of the vast majority of the
> ringing), and F=3.3 for "max" window mode (which suppresses ringing even
> further).
>
> Using our 0.045 - 110 GHz VNA system (Agilent HP8510XF), we have performed
> some measurements that do seem to indicate a 4-9 ps risetime(!!) can in fact
> be achieved as the equations would suggest for the minimum and normal window
> modes respectively. This, plus the availability of good calibration methods
> and structures up to these frequencies, makes for quite an impressive TDR
> tool, though it is in some ways more cumbersome than a scope with a TDR
> head.
>
> - Erik
>
> ==================================================================
> Erik Daniel, Ph.D. Voice: (507) 538-5461
> Mayo Foundation Fax: (507) 284-9171
> 200 First Street SW E-mail: daniel.erik@xxxxxxxx
> Rochester, MN 55905 Web: www.mayo.edu/sppdg/
> ==================================================================
>
>
> > -----Original Message-----
> > From: Lewandowski, Bob [mailto:blewandowski@xxxxxxxxxxxxxxxxxxxx]
> > Sent: Wednesday, October 30, 2002 5:24 PM
> > To: istvan.novak@xxxxxxxxxxxxxxxx;
> > jan.vercammen.jv1@xxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: spatial resolution and effective rise
> > time of VNA with TDR time-domain option
> >
> >
> >
> > I think the bandwidth for the .35/Tr estimate is
> > significantly narrower
> > than the NWA stop frequency would indicate. The end of the sweep is
> > effectively a filter with infinite attenuation beyond the stop
> > frequency. If this band shape is converted to the time
> > domain something
> > called Gibbs phenomenon occurs and produces ringing artifacts in the
> > time domain. As a result the measured response is filtered to
> > essentially reduce the amplitude response at the stop
> > frequency to have
> > no effect on the time domain response. I believe the filter shape can
> > be selected and it will dramatically effect the time response.
> >
> > ---Bob Lewandowski
> > Stratos Lightwave
> >
> >
> > > -----Original Message-----
> > > From: istvan novak [mailto:istvan.novak@xxxxxxxxxxxxxxxx]
> > > Sent: Wednesday, October 30, 2002 5:47 AM
> > > To: jan.vercammen.jv1@xxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: spatial resolution and effective rise=20
> > > time of VNA
> > > with TDR time-domain option
> > >=20
> > >=20
> > >=20
> > > Hi Jan,
> > >=20
> > > My 2 cents:
> > > As you noted, the spatial resolution is different for=20
> > > different Dk media,
> > > so probably it is more effective to stay with
> > bandwidth/risetime. The
> > > complications there are that VNAs
> > > - do not work all the way down to DC
> > > - usually have a range of windowing options for IFFT
> > >=20
> > > The fact that VNAs dont include DC in their frequency range is
> > > less of a problem when you want to resolve closely spaced
> > > discontinuities, but it creates an uncertainty of baseline if you
> > > have to do post processing.
> > >=20
> > > Windowing options may include flat, Hamming-like and Bessel-like
> > > windows. Their leakage is different, and it will directly
> > affect the
> > > spatial resolution.
> > >=20
> > > With a 'typical' windowing, the first approximation of BW=3D0.35/tr
> > > is a good start, and you could substitute the upper frequency end
> > > of the sweep to BW, and get the equivalent tr.
> > >=20
> > > The benefit of using VNAs for TDR is that you can do a full
> > > calibration up to the probe tips, if you want to, otherwise it is
> > > usually more limited in resolution compared to true TDR.
> > >=20
> > > regards
> > >=20
> > > Istvan novak
> > > SUN Microsystems
> > >=20
> > >=20
> > > ----- Original Message -----
> > > From: "Jan Vercammen" <jan.vercammen.jv1@xxxxxxxxxxxxxxxx>
> > > To: <si-list@xxxxxxxxxxxxx>
> > > Sent: Wednesday, October 30, 2002 7:57 AM
> > > Subject: [SI-LIST] spatial resolution and effective rise time=20
> > > of VNA with
> > > TDR time-domain option
> > >=20
> > >=20
> > > >
> > > > Hello SI-list,
> > > >
> > > > I have a question about the saptial resolution of vector=20
> > > network analysers
> > > > (VNA)
> > > > with time-domain TDR option, that is, to resolve
> > discontinuitites in
> > > > space (=3Dlength dimension)
> > > >
> > > > Is there a rule of thumb for estimating the spatial=20
> > > resolution of a VNA
> > > > with a
> > > > TDR time-domain option from knowlegde of its bandwith BW.
> > > >
> > > > I have found one rule in an application note: 15cm/BW(Ghz).=20
> > > For example,
> > > > for a 6GHz
> > > > BW the spatial resolution is about 2.5cm for an effective
> > dielectric
> > > > (dkeff) of 1.0.
> > > > You probably get better resolution for PCB or cable=20
> > > measurments. The rule
> > > > of thumb would become: 15cm/(sqrt(dkeff) BW(GHz).
> > > >
> > > > Another question concerns the relation between the VNA=20
> > > bandwith and the
> > > > available
> > > > effective rise time of the step or pulse of the time domain=20
> > > signals. I
> > > > assume that one
> > > > cannot use the rule trise=3D0.35/Bw because there BW
> > refers to the =
> > 3dB
> > > > breakpoint
> > > > (the effective BW is bigger). A VNA bandwith is its upper limit.
> > > >
> > > > -1- Is the above spatial resolution rule correct?
> > > > -2- Is there a rule of thumb to convert bandwith (BW) into=20
> > > an effective
> > > > rise time (10-90%)
> > > > of a VNA with a time-domain option?
> > > >
> > > >
> > > >
> > > >
> > > > Kind regards,
> > > >
> > > > Jan Vercammen
--
Daniel
ZZZ-dgun-ZZZ-@xxxxxxxxxxxxxxx
(remove the Z-'s to reply--they're what I do when I read spam)
--
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