[SI-LIST] Re: spatial resolution and effective rise time of VNA with TDR time-domain option
- From: "Lewandowski, Bob" <blewandowski@xxxxxxxxxxxxxxxxxxxx>
- To: <jeff.loyer@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 31 Oct 2002 15:45:32 -0600
In a past life I used the 8510 NWA TDR capability to spatially correlate
S-parameter data to the time domain to optimize the geometry of a low
reflection transition from coax to a small planar device. It was a slow
and tedious process, but we were able to build a structure that had 30db
return loss from dc to 18 GHz while transitioning from 7 mm coax to a 7
mil resistor.
The time domain gating capability is also very handy to extract the
S-parameters of a fixtured DUT while eliminating or reducing the
contributions of the fixture.
---Bob Lewandowski
Stratos Lightwave
> -----Original Message-----
> From: Loyer, Jeff [mailto:jeff.loyer@xxxxxxxxx]
> Sent: Thursday, October 31, 2002 8:38 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: spatial resolution and effective rise=20
> time of VNA
> with TDR time-domain option
>=20
>=20
>=20
> This brought up a question I have:
> Does anybody routinely use the "TDR option" of a VNA?
>=20
> I already had a TDR when I got our VNA. I tried the "TDR=20
> option" of the =3D
> VNA, but found it cumbersome, awkward, etc. (not to mention=20
> the sloooow =3D
> rise-time it forced). Kinda like using a 2x4 for a hammer -=20
> it works in =3D
> a pinch, but just barely, and not for everything. So, I'm=20
> real glad I =3D
> have both the TDR and VNA. I can't imagine using just the=20
> TDR option of =3D
> the VNA.
>=20
> Am I missing something? Have others had different experiences?
>=20
> Jeff Loyer
>=20
>=20
> -----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
>=20
>=20
>=20
> Hello SI-list,
>=20
> I have a question about the saptial resolution of vector network =3D
> analysers
> (VNA)
> with time-domain TDR option, that is, to resolve discontinuitites in
> space (=3D3Dlength dimension)
>=20
> 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.
>=20
> 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 measurments. The =
=3D
> rule
> of thumb would become: 15cm/(sqrt(dkeff) BW(GHz).
>=20
> 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 signals. I
> assume that one
> cannot use the rule trise=3D3D0.35/Bw because there BW refers to the =
3dB
> breakpoint
> (the effective BW is bigger). A VNA bandwith is its upper limit.
>=20
> -1- Is the above spatial resolution rule correct?
> -2- Is there a rule of thumb to convert bandwith (BW) into an=20
> effective
> rise time (10-90%)
> of a VNA with a time-domain option?
>=20
>=20
>=20
>=20
> Kind regards,
>=20
> Jan Vercammen
>=20
>=20
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