[SI-LIST] Re: spatial resolution and effective rise time of VNA with TDR time-domain option
- From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Thu, 31 Oct 2002 08:38:01 -0800
This brought up a question I have:
Does anybody routinely use the "TDR option" of a VNA?
I already had a TDR when I got our VNA. I tried the "TDR option" of the =
VNA, but found it cumbersome, awkward, etc. (not to mention the sloooow =
rise-time it forced). Kinda like using a 2x4 for a hammer - it works in =
a pinch, but just barely, and not for everything. So, I'm real glad I =
have both the TDR and VNA. I can't imagine using just the TDR option of =
the VNA.
Am I missing something? Have others had different experiences?
Jeff Loyer
-----Original Message-----
From: Jan Vercammen [mailto:jan.vercammen.jv1@xxxxxxxxxxxxxxxx]
Sent: Wednesday, October 30, 2002 4:58 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] spatial resolution and effective rise time of VNA
with TDR time-domain option
Hello SI-list,
I have a question about the saptial resolution of vector 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 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). 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 measurments. The =
rule
of thumb would become: 15cm/(sqrt(dkeff) BW(GHz).
Another question concerns the relation between the VNA bandwith and the
available
effective rise time of the step or pulse of the time domain 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 an effective
rise time (10-90%)
of a VNA with a time-domain option?
Kind regards,
Jan Vercammen
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