S11 of capacitor - UK Vintage Radio Repair and Restoration Discussion Forum

dmowziz · 28th Jul 2022, 7:48 pm

Hiii...

Trying to get s11 of a capacitor... This is what I did (not correct) :

I first determined the right width of strip for 50 ohms (about 3mm)

Then I used this width (first image), made the tape go abit to the other side of the board (ground)..
The sma is short circuited. I did port extension to make the trace appear as short (The closest I could get, 2nd image)

Then I cut a little bit of the tape at the end to attach the capacitor...

The data is off from expected (s parameter from manufacturer)...

Please kindly assist. GOHZU ?

Thanks!

Mark1960 · 28th Jul 2022, 8:42 pm

To measure SMT components its easier to take four SMT type SMA sockets. Leave one open, add two 100 ohm or 4 200 ohm to one as a 50 ohm load, then a blob of solder on one as a short. The fourth one can then be used to mount the component to be tested. Then calibrate the network analyser with the short open and load.

I think the loss in your stripline is probably having a big effect on your results.

dmowziz · 28th Jul 2022, 10:58 pm

Hi Mark, thanks... Didn't know there are SMT SMA sockets.

I have a calibration kit for the VNA

Mark1960 · 29th Jul 2022, 7:24 am

You can also use through hole SMA connectors and cut the pins close to the surface.

The advantage of making up a cal set with the same connectors as used to mount the capacitor is you then calibrate to the same mounting position.

You could also just use one connector for the capacitor, then after calibrating the network analyser with your cal kit, adjust the position of a short circuit across the capacitor as you did with your stripline.

28th Jul 2022, 7:48 pm	#1
dmowziz Pentode Join Date: Nov 2021 Location: Toronto, Canada Posts: 131	S11 of capacitor Hiii... Trying to get s11 of a capacitor... This is what I did (not correct) : I first determined the right width of strip for 50 ohms (about 3mm) Then I used this width (first image), made the tape go abit to the other side of the board (ground).. The sma is short circuited. I did port extension to make the trace appear as short (The closest I could get, 2nd image) Then I cut a little bit of the tape at the end to attach the capacitor... The data is off from expected (s parameter from manufacturer)... Please kindly assist. GOHZU ? Thanks! Attached Thumbnails Last edited by dmowziz; 28th Jul 2022 at 7:55 pm.

28th Jul 2022, 8:42 pm	#2
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,294	Re: S11 of capacitor To measure SMT components its easier to take four SMT type SMA sockets. Leave one open, add two 100 ohm or 4 200 ohm to one as a 50 ohm load, then a blob of solder on one as a short. The fourth one can then be used to mount the component to be tested. Then calibrate the network analyser with the short open and load. I think the loss in your stripline is probably having a big effect on your results.

28th Jul 2022, 10:58 pm	#3
dmowziz Pentode Join Date: Nov 2021 Location: Toronto, Canada Posts: 131	Re: S11 of capacitor Hi Mark, thanks... Didn't know there are SMT SMA sockets. I have a calibration kit for the VNA

29th Jul 2022, 7:24 am	#4
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,294	Re: S11 of capacitor You can also use through hole SMA connectors and cut the pins close to the surface. The advantage of making up a cal set with the same connectors as used to mount the capacitor is you then calibrate to the same mounting position. You could also just use one connector for the capacitor, then after calibrating the network analyser with your cal kit, adjust the position of a short circuit across the capacitor as you did with your stripline.