The author of the article uses a shielded box partition with a wall between them for isolation, so it could easily double the size of the nanoVNA, so the idea of an external add on for bench use makes more sense I think. See the second graphic below.
This would be a useful add on for the many of us with these small VNAs.
It could also be incorporated into a nanoVNA case. If it was permanently there, it would make sense to calibrate the vna for its presence permanently and add its presence to the FW. People could plug the calibration into the routines. Not very difficult. That would eliminate another source of error.
...
I think its possible to use relays to extend the functionality of a two port VNA to make an effective four port VNA too. (Or so I read in QEX a while ago)
Joe, the same relays are used as the tiny low voltage Omron ones you use in your switch box.
I think those were $10-$20 each. They work alright but the isolation was poor. I have an old Transco relay that I made up a really crappy DC-DC to drive it from the USB port. My software supports it. I plan to mount that along with a couple of bias-t's and maybe a decent step attenuator. But then I think, I should really add some mixers and some better couplers and maybe a wide band amp...... Reality always steps in.
The idea is that by reversing the two ports available with the very minimal differences possible, all four sets of S-parameters of a DUT become measurable.
(Thats what I meant by "four port" - I meant that the more VNA functionality is exploitable).
"While beta-testing his VNWA2.1 vector
network analyzer, Andreas Zimmermann,
DH7AZ, came up with a brilliant idea: He
took two RF relays and built a simple switch,
which could commutate the VNWA TX and
RX ports. (see refs below) Thus, a two port device wouldn't
have to be disconnected and turned manu-
ally any longer in order to measure its two
port S-parameters".
"Surprising to me, his first veroboard prototype already showed
good isolation values. Even more surprising
to me, the relay data sheet indicated that at
1.5 GHz, isolations of 60 dB could still be
expected. 2 That's when I decided to build
such a switching unit myself, and modify
my VNWA software so it would auto-
matically control the relays. This way, the
VNWA2 is turned into a full-featured two
port network analyzer. The most charming
aspect is the simplicity of the circuit, which
only requires two relays."This is from the article "A Simple S-Parameter Test
Set for the VNWA2 Vector Network Analyzer" in
QEX May 2009 by Dr. Thomas C. Baier, DG8SAQ
References he cites:
1 Professor Dr. Thomas C. Baier, DG8SAQ,
"A Small, Simple, USB-Powered Vector
Network Analyzer Covering 1 kHz to 1.3
GHz," QEX, Jan/Feb 2009, ARRL, pp 32 -
36. See also
www.arrl.org/qex/2009/01/Baier.pdf
2 Omron G6Y Relay, see w w w . o m r o n . c o m /
ecb/products/pdf/en-g6y.pdf
3 See, for example, Agilent AN 1287-3,
"Applying Error Correction to Network
Analyzer Measurements," Application Note,
http://cp.literature.agilent.com/litweb/pdf/5965-7709E.pdf
4 See
www.mydarc.de/DG8SAQ/NWA.html5 The VNWA software current as of the pub-
lication date of this article is available for
download from the ARRL QEX Web site. Go
to
www.arrl.org/qexfiles and look for the
file 5x09_Baier.zip
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There is a 3.3v version of the Omron relays.