s-params help

Post by john larkin
We might design an RF switch gadget. We work in time domain, but we
probably should specify VSWR or s-params or something. We have no gear
to do those sorts of measurements.
If someone has equipment to do reasonably accurate VNA measurements
(and I don't think they are usually super accurate!) we could use some
help.

an NanoVNA V3 is ~$100 on amazon

Cursitor Doom

2024-02-08 21:50:53 UTC

On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

There are other less inaccurate more expensive VNAs around these days.
And they can be had for a fraction of what you had to pay for a HP or
R&S VNA 30 years ago.
A relatively small expense could be justified on this occasion, I'd
have thought.

john larkin

2024-02-08 23:46:06 UTC

On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

Anthony William Sloman

2024-02-09 02:10:10 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

Bearing in mind that John Larkin won't be a particularly attractive customer. He isn't too specific about what he is asking for, or why he is asking for it - it looks as if he wants to be able to answer questions from customers who are better-informed than he is.

S-parameters are measured at single frequency and current, and time domain operation implies changing current and non-sinusoidal waveforms.

Delivering what he wants will involve a large chunk of educating him to point where he could ask the right questions, and he doesn't strike me as all that educatable.

--
Bill Sloman, Sydney

Cursitor Doom

2024-02-09 08:56:02 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

John Larkin

2024-02-09 15:52:32 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!

So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.

This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see.

https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

Cursitor Doom

2024-02-09 16:18:06 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see.
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

$880 wow! I can see why you would want to get a piece of that action.
I'm afraid my 2 VNAs top out at 1.3 and 3Ghz respectively. They're
both full-blown lab jobs made by HP but the frequency range is
virtually DC by today's standards. If you want to look at how switches
perform above 3Ghz then there's not much I can do, I'm afraid. I was
thinking about buying a third VNA to go up to 6Ghz, but I think that
would be a waste of money as I'm really not interested in anything
above 1.
I don't see how $1 telecom relays can *possibly* provide that kind of
bandwidth. Are you sure of your testing methodology?

John Larkin

2024-02-09 16:44:13 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see.
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

We might specify our switches for, say, 2.5 or 3 GHz, and only spec
VSWR up to there.

Post by Cursitor Doom
I don't see how $1 telecom relays can *possibly* provide that kind of
bandwidth. Are you sure of your testing methodology?

I'm looking at the TDR step response. I'm seeing about 117 pS rise
time. Correcting for the scope, that's 113 ps, 3.1 GHz.

https://www.dropbox.com/scl/fo/tryhmxo9krr52vfr94hjq/h?rlkey=fbgz789m4bo1e847tqe70fl8d&dl=0

The common port path looks a bit inductive, as you'd expect, so maybe
a tiny RC somewhere would help.

Cursitor Doom

2024-02-09 17:55:40 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see.
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

We might specify our switches for, say, 2.5 or 3 GHz, and only spec
VSWR up to there.

Post by Cursitor Doom
I don't see how $1 telecom relays can *possibly* provide that kind of
bandwidth. Are you sure of your testing methodology?

I'm looking at the TDR step response. I'm seeing about 117 pS rise
time. Correcting for the scope, that's 113 ps, 3.1 GHz.
https://www.dropbox.com/scl/fo/tryhmxo9krr52vfr94hjq/h?rlkey=fbgz789m4bo1e847tqe70fl8d&dl=0
The common port path looks a bit inductive, as you'd expect, so maybe
a tiny RC somewhere would help.

I know you know what you're doing so I won't argue on that point.
However, I personally wouldn't dream of using a TDR for this purpose.
I would sweep the switch across say 100khz through 3Ghz with a VNA and
if any impedence discontinuity showed up, *then* use the TDR to find
where it is.

Anthony William Sloman

2024-02-10 01:09:33 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see.
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

It the part is small and more or less coaxial it can provide that kind of bandwidth. I knew about that in the 1980s, though we never exploited it.
The parts were never designed for the application - they just happened to have good high frequency performance.

--
Bill Sloman, Sydney

Lasse Langwadt Christensen

2024-02-09 16:21:19 UTC

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

Cursitor Doom

2024-02-09 17:52:45 UTC

On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

Yes, it'll do that, but not to commercial standard accuracy, of
course. I bought one a while ago just out of curiosity to compare it
with the lab ones and was quite frankly *amazed* that they've done all
that for under a hundred bucks. It's not a serious instrument, but a
huge shot across the bows of the traditional manufacturers
nevertheless. They need to up their game or they won't survive.

bitrex

2024-02-09 18:27:11 UTC

Post by Cursitor Doom
On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

I was doing some measurements late last year of microstrip,
experimenting with using the NanoVNA-H4 port extension feature to
flatten the S21 phase response and using that to estimate the relative
permittivity of the microstrip substrate, and comparing against a
university lab Keysight 5080.

In that role the NanoVNA looks pretty good up to about 800 MHz but at 1
GHz and above it starts to be pretty suspect and everything above 1.5 is
complete nonsense. Haven't tried the NanoVNA 2, the -H4 has about 40dB
dynamic range on a good day at 1 GHz and the version 2 claims 90.

The Keysight is IIRC specced at about 130 or something there but a 6 GHz
class 5080 cost what, $100,000 new?

Cursitor Doom

2024-02-09 18:41:31 UTC

Post by Cursitor Doom
On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

I was doing some measurements late last year of microstrip,
experimenting with using the NanoVNA-H4 port extension feature to
flatten the S21 phase response and using that to estimate the relative
permittivity of the microstrip substrate, and comparing against a
university lab Keysight 5080.
In that role the NanoVNA looks pretty good up to about 800 MHz but at 1
GHz and above it starts to be pretty suspect and everything above 1.5 is
complete nonsense. Haven't tried the NanoVNA 2, the -H4 has about 40dB
dynamic range on a good day at 1 GHz and the version 2 claims 90.
The Keysight is IIRC specced at about 130 or something there but a 6 GHz
class 5080 cost what, $100,000 new?

My main HP VNA (can't recall the model number off hand) did cost
around 100k - and that was over 30 years ago! I've no idea what the
equivalent would be today; no idea whatsoever.
It's a fascinating hobby. You can characterize all sorts of things
with a VNA: cables, adaptors, filters, dummy loads, microstrip,
transformers, switches. Basically anything you might find in a signal
path of a transmission line. It became something of an obsession in my
case. Fortunately there are worse things one can get obsessed over and
this is a totally harmless pursuit.

bitrex

2024-02-09 18:50:42 UTC

Post by Cursitor Doom
On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

I was doing some measurements late last year of microstrip,
experimenting with using the NanoVNA-H4 port extension feature to
flatten the S21 phase response and using that to estimate the relative
permittivity of the microstrip substrate, and comparing against a
university lab Keysight 5080.
In that role the NanoVNA looks pretty good up to about 800 MHz but at 1
GHz and above it starts to be pretty suspect and everything above 1.5 is
complete nonsense. Haven't tried the NanoVNA 2, the -H4 has about 40dB
dynamic range on a good day at 1 GHz and the version 2 claims 90.
The Keysight is IIRC specced at about 130 or something there but a 6 GHz
class 5080 cost what, $100,000 new?

My main HP VNA (can't recall the model number off hand) did cost
around 100k - and that was over 30 years ago! I've no idea what the
equivalent would be today; no idea whatsoever.

Used examples of the 6 GHz machine (they go up to 50!) are going for
about 30k USD so probably not far off, they're a few year old now.

They seem to run Windows 7. Crash to Windows 7, too!

Post by Cursitor Doom
It's a fascinating hobby. You can characterize all sorts of things
with a VNA: cables, adaptors, filters, dummy loads, microstrip,
transformers, switches. Basically anything you might find in a signal
path of a transmission line. It became something of an obsession in my
case. Fortunately there are worse things one can get obsessed over and
this is a totally harmless pursuit.

I can use the NanoVNA 1.0 to tell you from a ~30 cm piece of microstrip
on FR4, that FR4 has a relative permittivity somewhere between 3 and 5!

Not exactly earth-shaking information but to do better in theory with
that box you'd need a longer strip, but then errors from other sources
start coming in..

john larkin

2024-02-09 18:59:29 UTC

Post by Cursitor Doom
On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

I was doing some measurements late last year of microstrip,
experimenting with using the NanoVNA-H4 port extension feature to
flatten the S21 phase response and using that to estimate the relative
permittivity of the microstrip substrate, and comparing against a
university lab Keysight 5080.
In that role the NanoVNA looks pretty good up to about 800 MHz but at 1
GHz and above it starts to be pretty suspect and everything above 1.5 is
complete nonsense. Haven't tried the NanoVNA 2, the -H4 has about 40dB
dynamic range on a good day at 1 GHz and the version 2 claims 90.
The Keysight is IIRC specced at about 130 or something there but a 6 GHz
class 5080 cost what, $100,000 new?

One can buy cheap multilayer PCBs these days, and could pack many
experiments onto one board.

I spent a bit of time playing with pcb layouts for edge-launch SMA
connectors. I did that with ATLC and TDR. There are some pretty good
$2 connectors.

Cursitor Doom

2024-02-09 20:29:34 UTC

Post by john larkin

Post by Cursitor Doom
On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

I was doing some measurements late last year of microstrip,
experimenting with using the NanoVNA-H4 port extension feature to
flatten the S21 phase response and using that to estimate the relative
permittivity of the microstrip substrate, and comparing against a
university lab Keysight 5080.
In that role the NanoVNA looks pretty good up to about 800 MHz but at 1
GHz and above it starts to be pretty suspect and everything above 1.5 is
complete nonsense. Haven't tried the NanoVNA 2, the -H4 has about 40dB
dynamic range on a good day at 1 GHz and the version 2 claims 90.
The Keysight is IIRC specced at about 130 or something there but a 6 GHz
class 5080 cost what, $100,000 new?

One can buy cheap multilayer PCBs these days, and could pack many
experiments onto one board.
I spent a bit of time playing with pcb layouts for edge-launch SMA
connectors. I did that with ATLC and TDR. There are some pretty good
$2 connectors.

This is the main one I have:
https://disk.yandex.com/i/EzucNyjT8vRbtA

It is extendable up to 6Ghz but there's no point since both the S
parameter test sets I have are limited to 3. The fixture on the front
is for testing RF transistors, which was the last thing I used it for.
If you want me to check out your switch, I'm happy to help. It's just
that the postage to Yurp from SF will be a bit of a killer I'd
imagine. If you plan on doing much of this kind of thing you're going
to have to bite the bullet and splash out on one to keep, because
doing the necessary tweaks to get your DUT in spec will necessitate
repeated testing which is impractical if you don't have a VNA to hand
and have to send the thing to someone else every single time!

john larkin

2024-02-09 18:22:23 UTC

On Fri, 9 Feb 2024 08:21:19 -0800 (PST), Lasse Langwadt Christensen

Post by Cursitor Doom
On Thu, 8 Feb 2024 13:27:10 -0800 (PST), Lasse Langwadt Christensen

an NanoVNA V3 is ~$100 on amazon

I just want someone to do this for me.

What frequency range? I might be able to assist here.

My switches seem to have about a 3 GHz bandwidth, based on their TDR
response. I'm using $1 telecom relays!
So I might want to measure a few s-params from some lowish frequency
to, say, 5 GHz. I'd only want a few S11 S21 and S22's to put on a data
sheet.
This one just specifies three simple params, presumably over its freq
range. Maybe that's all people want to see. z
https://www.pasternack.com/bnc-electromechanical-ab-coaxial-switch-1ghz-5watts-12volts-pe7100-p.aspx

I'm quite sure the NanoVNA can give you S11, S21, that's what's plotted on the curves
I think I have one laying around somewhere, so I might try it

Looks like a lot of people who make RF switches just specify VSWR and
isolation. That's probably all I'd need to measure.

Jeroen Belleman

2024-02-08 22:57:19 UTC