Re: [SI-LIST] : Diff measurements with VNA

John V Fitzpatrick (John.Fitzpatrick@ln.cit.alcatel.fr)
Wed, 25 Feb 1998 18:31:29 +0100

If you've a HP8753A, this should work:

Say you're measuring S21 for a diff pair (A+,A-) to (B+,B-).

- Terminate A-, B-. Measure S21 A+ -> B+. Store in memory.
- Terminate A-, B+. Measure S21 A+ -> B-.
- Subtract data from memory to get differential S21 for the pair.

John

fabrizio zanella wrote:
>
> Katie,
> how many ports are you trying to measure, two or four? What is your
> frequency range?
> If you need more than 2 ports, multiport measurements with a VNA is not an
> easy task. I had looked into it a few years ago, and at the time you could
> only take 2 port measurements with a VNA. None of the manufacturers (HP,
> Wiltron) could support multiport measurements with a VNA, so you could only
> measure return loss, insertion loss, and coupling between 2 lines.
> I do know that a couple of engineers have written software and created
> hardware to create a multiport network analyzer, but I believe these were
> internal efforts, so you'd have a hard time purchasing an off the shelf
> solution.
> If you only need two ports, to measure differential reflection of the pair,
> you will still need to find some software which can take one of the VNA
> signals and invert it in phase, to create a differential pair. Any
> thoughts on this?
> I remember there used to be a newsletter on VNA measurement techniques
> called 'MAMA's Notes', I don't recall who published it. I would try your
> HP sales rep, ask for application notes and companies they may be working
> with that have done this before.
>
> Hope this helps
> Fabrizio Zanella
> Hardware Engineering
> email: fzanella@emc.com
> (508) 435-1000 Ext. 4645
> Fax: (508) 435-8949
> EMC Corporation
> 171 South Street
> Hopkinton, MA 01748-9103
>
> -------------
> Original Text
> From: "Katie Rothstein" <Katie_Rothstein@notes.teradyne.com>, on 2/25/98
> 11:10 AM:
> To: smtp@Eng@EMCHOP1[<si-list@silab.Eng.Sun.COM>]
>
> If anyone could point me in some direction regarding differential
> measurements
> with a Network Analyzer I would greatly appreciate it. I'm starting from
> the
> ground floor here, so thoughts, information, or possible sources would be
> helpful! Thank you!
> -Katie Rothstein
> Teradyne, Inc.
> (603) 791-3488