|
W. Reeve, T. Hagen, K. Poulsen published some data from and described their techniques of measuring ferrite beads in "Radio Astronomy Magazine" in 2013. They did a lot of work developing test fixtures and error analysis. You can find their papers at :
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Hi Starsekr and others Pay special attention to Part III. Part I and Part II are describing out learning process. The toroide measurements are "handicap'ed" by the wire loop inductance which you only can eliminate by mesurmetn in a closed chamber where the inductance of the wire/rod passing thru the toroide can be subtracted in a spreadsheet calculation. In Part II the is a reference to a HP document which explain the mathematic on page 21 / 22 but the link I here provide is for the new version which is far poorer writing than the "old one" I used when we wrote the articles and which has some errors as well. I also provide a link to an excellent article far better understandable. Ling to where a pdf file can be downloaded for the document "Method for measuring complex permeability at radio frequencies" Link to the document "Measurement of Complex Permeability Using Short Coaxial Line Reflection Method" Have fun Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af Starsekr via Groups.Io Sendt: 19. oktober 2019 09:35 Til: [email protected]Emne: [nanovna-users] Measuring ferrite beads #test-jig W. Reeve, T. Hagen, K. Poulsen published some data from and described their techniques of measuring ferrite beads in "Radio Astronomy Magazine" in 2013. They did a lot of work developing test fixtures and error analysis. You can find their papers at :
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Wondeful, that is exactly what I was looking for !!
Thanks for the link !!!
?TypeApp for Android herunterladen ?
Am 19. Okt. 2019, 09:35, um 09:35, "Starsekr via Groups.Io" <starsekr@...> schrieb:
toggle quoted message
Show quoted text
W. Reeve, T. Hagen, K. Poulsen published some data from and described
their techniques of measuring ferrite beads in "Radio Astronomy
Magazine" in 2013. They did a lot of work developing test fixtures
and error analysis. You can find their papers at :
|
Hi Starsekr and All,
Another test jig for measuring Ferrite is shown here:
There is also a section describing process for plotting Complex Permeability using SimSmith. The example compares measured complex permeability to Fair-Rite published data.
John KN5L
|
Hello Kurt,
that is a wonderful description of what you three did a while go when measuring the performance of ferrite materials. Very cool stuff and because I'm just looking in exactly that topic I have a few questions questions to your fixture. I'm still on a "beginner level" using VNA for measuring ferrite impedances, so sorry for any stupid questiosn.
When you have inserted the ferrite bead and turning the adjustment knob it will contact the SMA F connector at some point. What type of SMA connector did you use? I would imagin that the inner conductor gets damaged pretty fast after using the fixture a few times? Or is that a "special" type of SMA with more robust inner-conductor design ?
Do you know if something similar is commercially available?
Secondly, I like to characterize the ferrits with DC-BIAS current from 0 up to 10 Amps.. That changes ferrite impedance and frequency, depending on saturation of the material.
See
For relatively large ferrite cores it might be easy just adding an additional wire through the inner dimeter, with a DC-current. That way the RF- and DC wires are separated.
But for smaller components like wound-beads (e.g. Fair-Rite 2961666671) I need to "inject" the DC current into the signal line of the VNA. Do you have any experience how to do that best? What kind of RF-filtering / DC-blocking needs to be build ? How is calibration performed then? The additional filtering will definitely change the overall S11 response, but I want to see only the ferrite effect on the Impedance and not any effect of that filter. The intended frequency range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz.
|
I have had good luck with this home brew fixture using copper clad, N panel mount connectors, BNC adapters and a flexible conductor wire that can be detached on on side using some old cannon connector pins. I did modify my idea several months ago from reading the three articles mentioned in other posts. It definitely works to distinguish ferrite types.
My findings are that type 31 mix will work as great common mode chokes down to 160 meters and up. Type 43 will attenuate common mode from mid HF up.
Spent a few hours going through the door with about 50 mystery ²ú±ð²¹»å²õ/²õ²Ô²¹±è-´Ç²Ô¡¯²õ.
My method of marking the beads with a grey marker is finding the 3 dB and 6db points on any given bead and writing the frequency next to them.
Run the cal routine with fixture installed. I use the bottom two bnc¡¯s that are pass throughs for the 50 and short load cal.
Gary
KT7AZ
|
I do one more thing when I finish the sorting, I stand them up close
together and spray paint the end gently with a color matching the first
number of the mix. 31 is orange, 43 is yellow etc. The marking on the
sides get worn off some times but the paint holds up really well and easy
to physically sort later.
Mel, K6KBE
toggle quoted message
Show quoted text
On Sun, Oct 20, 2019 at 7:29 AM KT7AZ <kt7az.v69@...> wrote: I have had good luck with this home brew fixture using copper clad, N
panel mount connectors, BNC adapters and a flexible conductor wire that can
be detached on on side using some old cannon connector pins. I did modify
my idea several months ago from reading the three articles mentioned in
other posts. It definitely works to distinguish ferrite types.
My findings are that type 31 mix will work as great common mode chokes
down to 160 meters and up. Type 43 will attenuate common mode from mid HF
up.
Spent a few hours going through the door with about 50 mystery
²ú±ð²¹»å²õ/²õ²Ô²¹±è-´Ç²Ô¡¯²õ.
My method of marking the beads with a grey marker is finding the 3 dB and
6db points on any given bead and writing the frequency next to them.
Run the cal routine with fixture installed. I use the bottom two bnc¡¯s
that are pass throughs for the 50 and short load cal.
Gary
KT7AZ
|
Hi Ulrich First of all I give you the link to another document not published but in small "circles" and it will interest you I am sure to the Test Chamber and Measurements above 500MHz.pdf It might be entered in the browser directly as the io groups messages does no like my notation ? Regarding the adaptor, to which the male centerpin is engaging, is a straight forward threaded SMA female female adaptor with a hex nut on either side of the top plate, with a toothed washer on the top side. For the male centerpin to find the female center bushing I just press inserted a small 2mm long section of the Teflon part for a male SMA adaptor. It has a hole of 1 mm and that is enough guidance for the male pin to home in on the female bushing. I insert an image of both sides, and in my case it was a bulkhead adaptor used but it does not matter what you use. No wear to consider. Just for the fun of it I show you my mico-chamber Regarding the DC biasing I have no experience, but I do not see a big problem in that either. The center pin resistance is very low so not much DC blocking required to protect the VNWA TX out. The biggest problem is to know the impedance of the RF isolation between the DC supply and the center pin to be high enough. I imagine a SMA T adaptor and some sort of resistive or inductive impedance to block the low impedance of the DC supply. The impedance of the T adaptor seen from the RF isolation is removed by the calibration on the output side of the T-adaptor connected to the test chamber (with no DC current applied). So the impedance for determining the inductance of the internal ground rod without the toroid and with toroid is straight forward measurement as such. How many Amps the SMA adaptors can carry is a matter for studying. In my last mail I said some nonsense about the spreadsheet, which is used for determining the rod impedance and that only. How to subtract the inductance for the measurement with toroid is a matter of some mathematics I think is covered by already available material else revert to the matter Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af UlrichKraft Sendt: 20. oktober 2019 15:25 Til: [email protected]Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Hello Kurt, that is a wonderful description of what you three did a while go when measuring the performance of ferrite materials. Very cool stuff and because I'm just looking in exactly that topic I have a few questions questions to your fixture. I'm still on a "beginner level" using VNA for measuring ferrite impedances, so sorry for any stupid questiosn. When you have inserted the ferrite bead and turning the adjustment knob it will contact the SMA F connector at some point. What type of SMA connector did you use? I would imagin that the inner conductor gets damaged pretty fast after using the fixture a few times? Or is that a "special" type of SMA with more robust inner-conductor design ? Do you know if something similar is commercially available? Secondly, I like to characterize the ferrits with DC-BIAS current from 0 up to 10 Amps.. That changes ferrite impedance and frequency, depending on saturation of the material. See For relatively large ferrite cores it might be easy just adding an additional wire through the inner dimeter, with a DC-current. That way the RF- and DC wires are separated. But for smaller components like wound-beads (e.g. Fair-Rite 2961666671) I need to "inject" the DC current into the signal line of the VNA. Do you have any experience how to do that best? What kind of RF-filtering / DC-blocking needs to be build ? How is calibration performed then? The additional filtering will definitely change the overall S11 response, but I want to see only the ferrite effect on the Impedance and not any effect of that filter. The intended frequency range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz.
|
Sorry the link does not open???
Mel, K6KBE
toggle quoted message
Show quoted text
On Sun, Oct 20, 2019 at 8:54 AM Kurt Poulsen <kurt@...> wrote: Hi Ulrich
First of all I give you the link to another document not published but in
small "circles" and it will interest you I am sure
to the Test Chamber and Measurements
above 500MHz.pdf
It might be entered in the browser directly as the io groups messages does
no like my notation ?
Regarding the adaptor, to which the male centerpin is engaging, is a
straight forward threaded SMA female female adaptor with a hex nut on
either side of the top plate, with a toothed washer on the top side.
For the male centerpin to find the female center bushing I just press
inserted a small 2mm long section of the Teflon part for a male SMA
adaptor. It has a hole of 1 mm and that is enough guidance for the male pin
to home in on the female bushing. I insert an image of both sides, and in
my case it was a bulkhead adaptor used but it does not matter what you use.
No wear to consider.
Just for the fun of it I show you my mico-chamber
Regarding the DC biasing I have no experience, but I do not see a big
problem in that either. The center pin resistance is very low so not much
DC blocking required to protect the VNWA TX out. The biggest problem is to
know the impedance of the RF isolation between the DC supply and the center
pin to be high enough. I imagine a SMA T adaptor and some sort of resistive
or inductive impedance to block the low impedance of the DC supply. The
impedance of the T adaptor seen from the RF isolation is removed by the
calibration on the output side of the T-adaptor connected to the test
chamber (with no DC current applied). So the impedance for determining the
inductance of the internal ground rod without the toroid and with toroid is
straight forward measurement as such. How many Amps the SMA adaptors can
carry is a matter for studying.
In my last mail I said some nonsense about the spreadsheet, which is used
for determining the rod impedance and that only. How to subtract the
inductance for the measurement with toroid is a matter of some mathematics
I think is covered by already available material else revert to the matter
Kind regards
Kurt
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af
UlrichKraft
Sendt: 20. oktober 2019 15:25
Til: [email protected]
Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig
Hello Kurt,
that is a wonderful description of what you three did a while go when
measuring the performance of ferrite materials. Very cool stuff and because
I'm just looking in exactly that topic I have a few questions questions to
your fixture. I'm still on a "beginner level" using VNA for measuring
ferrite impedances, so sorry for any stupid questiosn.
When you have inserted the ferrite bead and turning the adjustment knob
it will contact the SMA F connector at some point. What type of SMA
connector did you use? I would imagin that the inner conductor gets damaged
pretty fast after using the fixture a few times? Or is that a "special"
type of SMA with more robust inner-conductor design ?
Do you know if something similar is commercially available?
Secondly, I like to characterize the ferrits with DC-BIAS current from 0
up to 10 Amps.. That changes ferrite impedance and frequency, depending on
saturation of the material.
See
For relatively large ferrite cores it might be easy just adding an
additional wire through the inner dimeter, with a DC-current. That way the
RF- and DC wires are separated.
But for smaller components like wound-beads (e.g. Fair-Rite 2961666671) I
need to "inject" the DC current into the signal line of the VNA. Do you
have any experience how to do that best? What kind of RF-filtering /
DC-blocking needs to be build ? How is calibration performed then? The
additional filtering will definitely change the overall S11 response, but I
want to see only the ferrite effect on the Impedance and not any effect of
that filter. The intended frequency range is up to 500 MHz for #61
material, but ideally for full span of nanovna up to 1 GHz.
|
Hi Urrich I think it is worth mentioning that only when a toroid/clamp is measured in a closed chamber the true charcteristics of the material is measured. Using an open air loop you are "fooling yourself" as field lined are escaping. This statement might get someone to protest, as they have so and so good experience but fact is fact. We got Fair Rite to admit it was not the true characteristics for the material they published, but that was the best they could do (at that time) using a short wire thru a test core. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af UlrichKraft Sendt: 20. oktober 2019 15:25 Til: [email protected]Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Hello Kurt, that is a wonderful description of what you three did a while go when measuring the performance of ferrite materials. Very cool stuff and because I'm just looking in exactly that topic I have a few questions questions to your fixture. I'm still on a "beginner level" using VNA for measuring ferrite impedances, so sorry for any stupid questiosn. When you have inserted the ferrite bead and turning the adjustment knob it will contact the SMA F connector at some point. What type of SMA connector did you use? I would imagin that the inner conductor gets damaged pretty fast after using the fixture a few times? Or is that a "special" type of SMA with more robust inner-conductor design ? Do you know if something similar is commercially available? Secondly, I like to characterize the ferrits with DC-BIAS current from 0 up to 10 Amps.. That changes ferrite impedance and frequency, depending on saturation of the material. See For relatively large ferrite cores it might be easy just adding an additional wire through the inner dimeter, with a DC-current. That way the RF- and DC wires are separated. But for smaller components like wound-beads (e.g. Fair-Rite 2961666671) I need to "inject" the DC current into the signal line of the VNA. Do you have any experience how to do that best? What kind of RF-filtering / DC-blocking needs to be build ? How is calibration performed then? The additional filtering will definitely change the overall S11 response, but I want to see only the ferrite effect on the Impedance and not any effect of that filter. The intended frequency range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz.
|
Hi Mel Please copy from .. Until pdf and paste into your URL in a browser. Watch out for the inserted > Then it works Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af Mel Farrer, K6KBE Sendt: 20. oktober 2019 18:05 Til: [email protected]Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Sorry the link does not open??? Mel, K6KBE
On Sun, Oct 20, 2019 at 8:54 AM Kurt Poulsen <kurt@...> wrote: Hi Ulrich
First of all I give you the link to another document not published but
in small "circles" and it will interest you I am sure
to the Test Chamber and Measurements
above 500MHz.pdf It might be entered in the browser directly as the io
groups messages does no like my notation ?
Regarding the adaptor, to which the male centerpin is engaging, is a
straight forward threaded SMA female female adaptor with a hex nut on
either side of the top plate, with a toothed washer on the top side.
For the male centerpin to find the female center bushing I just press
inserted a small 2mm long section of the Teflon part for a male SMA
adaptor. It has a hole of 1 mm and that is enough guidance for the
male pin to home in on the female bushing. I insert an image of both
sides, and in my case it was a bulkhead adaptor used but it does not matter what you use.
No wear to consider.
Just for the fun of it I show you my mico-chamber Regarding the DC
biasing I have no experience, but I do not see a big problem in that
either. The center pin resistance is very low so not much DC blocking
required to protect the VNWA TX out. The biggest problem is to know
the impedance of the RF isolation between the DC supply and the center
pin to be high enough. I imagine a SMA T adaptor and some sort of
resistive or inductive impedance to block the low impedance of the DC
supply. The impedance of the T adaptor seen from the RF isolation is
removed by the calibration on the output side of the T-adaptor
connected to the test chamber (with no DC current applied). So the
impedance for determining the inductance of the internal ground rod
without the toroid and with toroid is straight forward measurement as
such. How many Amps the SMA adaptors can carry is a matter for studying.
In my last mail I said some nonsense about the spreadsheet, which is
used for determining the rod impedance and that only. How to subtract
the inductance for the measurement with toroid is a matter of some
mathematics I think is covered by already available material else
revert to the matter Kind regards Kurt
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af
UlrichKraft
Sendt: 20. oktober 2019 15:25
Til: [email protected]
Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig
Hello Kurt,
that is a wonderful description of what you three did a while go when
measuring the performance of ferrite materials. Very cool stuff and
because I'm just looking in exactly that topic I have a few questions
questions to your fixture. I'm still on a "beginner level" using VNA
for measuring ferrite impedances, so sorry for any stupid questiosn.
When you have inserted the ferrite bead and turning the adjustment
knob it will contact the SMA F connector at some point. What type of
SMA connector did you use? I would imagin that the inner conductor
gets damaged pretty fast after using the fixture a few times? Or is that a "special"
type of SMA with more robust inner-conductor design ?
Do you know if something similar is commercially available?
Secondly, I like to characterize the ferrits with DC-BIAS current from
0 up to 10 Amps.. That changes ferrite impedance and frequency,
depending on saturation of the material.
See
cable-emi-suppression-cores/ For relatively large ferrite cores it
might be easy just adding an additional wire through the inner
dimeter, with a DC-current. That way the
RF- and DC wires are separated.
But for smaller components like wound-beads (e.g. Fair-Rite
2961666671) I need to "inject" the DC current into the signal line of
the VNA. Do you have any experience how to do that best? What kind of
RF-filtering / DC-blocking needs to be build ? How is calibration
performed then? The additional filtering will definitely change the
overall S11 response, but I want to see only the ferrite effect on the
Impedance and not any effect of that filter. The intended frequency
range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz.
|
Mel, sometimes Kurt¡¯s links don¡¯t complete properly, even though all the words are there. Let¡¯s see if this works:
to the Test Chamber and Measurements above 500MHz.pdf
If not, try this :
Jeff
|
That worked, thanks.
Mel, K6KBE
toggle quoted message
Show quoted text
On Sun, Oct 20, 2019 at 9:14 AM Kurt Poulsen <kurt@...> wrote: Hi Mel
Please copy from .. Until pdf and paste into your URL in a
browser. Watch out for the inserted >
Then it works
Kind regards
Kurt
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af Mel
Farrer, K6KBE
Sendt: 20. oktober 2019 18:05
Til: [email protected]
Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig
Sorry the link does not open???
Mel, K6KBE
On Sun, Oct 20, 2019 at 8:54 AM Kurt Poulsen <kurt@...> wrote:
Hi Ulrich
First of all I give you the link to another document not published but
in small "circles" and it will interest you I am sure
to the Test Chamber and Measurements
above 500MHz.pdf It might be entered in the browser directly as the io
groups messages does no like my notation ?
Regarding the adaptor, to which the male centerpin is engaging, is a
straight forward threaded SMA female female adaptor with a hex nut on
either side of the top plate, with a toothed washer on the top side.
For the male centerpin to find the female center bushing I just press
inserted a small 2mm long section of the Teflon part for a male SMA
adaptor. It has a hole of 1 mm and that is enough guidance for the
male pin to home in on the female bushing. I insert an image of both
sides, and in my case it was a bulkhead adaptor used but it does not matter what you use.
No wear to consider.
Just for the fun of it I show you my mico-chamber Regarding the DC
biasing I have no experience, but I do not see a big problem in that
either. The center pin resistance is very low so not much DC blocking
required to protect the VNWA TX out. The biggest problem is to know
the impedance of the RF isolation between the DC supply and the center
pin to be high enough. I imagine a SMA T adaptor and some sort of
resistive or inductive impedance to block the low impedance of the DC
supply. The impedance of the T adaptor seen from the RF isolation is
removed by the calibration on the output side of the T-adaptor
connected to the test chamber (with no DC current applied). So the
impedance for determining the inductance of the internal ground rod
without the toroid and with toroid is straight forward measurement as
such. How many Amps the SMA adaptors can carry is a matter for studying.
In my last mail I said some nonsense about the spreadsheet, which is
used for determining the rod impedance and that only. How to subtract
the inductance for the measurement with toroid is a matter of some
mathematics I think is covered by already available material else
revert to the matter Kind regards Kurt
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af
UlrichKraft
Sendt: 20. oktober 2019 15:25
Til: [email protected]
Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig
Hello Kurt,
that is a wonderful description of what you three did a while go when
measuring the performance of ferrite materials. Very cool stuff and
because I'm just looking in exactly that topic I have a few questions
questions to your fixture. I'm still on a "beginner level" using VNA
for measuring ferrite impedances, so sorry for any stupid questiosn.
When you have inserted the ferrite bead and turning the adjustment
knob it will contact the SMA F connector at some point. What type of
SMA connector did you use? I would imagin that the inner conductor
gets damaged pretty fast after using the fixture a few times? Or is that a "special"
type of SMA with more robust inner-conductor design ?
Do you know if something similar is commercially available?
Secondly, I like to characterize the ferrits with DC-BIAS current from
0 up to 10 Amps.. That changes ferrite impedance and frequency,
depending on saturation of the material.
See
cable-emi-suppression-cores/ For relatively large ferrite cores it
might be easy just adding an additional wire through the inner
dimeter, with a DC-current. That way the
RF- and DC wires are separated.
But for smaller components like wound-beads (e.g. Fair-Rite
2961666671) I need to "inject" the DC current into the signal line of
the VNA. Do you have any experience how to do that best? What kind of
RF-filtering / DC-blocking needs to be build ? How is calibration
performed then? The additional filtering will definitely change the
overall S11 response, but I want to see only the ferrite effect on the
Impedance and not any effect of that filter. The intended frequency
range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz.
|
Kurt, Just read your comment above. I think you said it works by Magic, Which I believe. I will have to get a bit of experimenting experience before I try ferrite beads I think.
Jim, KA6TPR
|
Hi Jim There is no substitute to hard work. Besides I have a Magic Wand ? Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af Starsekr via Groups.Io Sendt: 21. oktober 2019 10:28 Til: [email protected]Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Kurt, Just read your comment above. I think you said it works by Magic, Which I believe. I will have to get a bit of experimenting experience before I try ferrite beads I think. Jim, KA6TPR
|
Kurt, thanks again for your explanations and pictures.
Now I have to experiment for a while and build a suitable fixture and see what the resuts are. I don't want to overdo it too much, primarily I need a good and reasonabe accuracy to compare ferrits for EMC applications of various manufactureres.
Once more thanks, and I'm sure at some point of time I will have more questions.... or even results.
Always great help to have someone experienced here.
|
Hi Ulrich Great. Looking forward to follow the progress Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af UlrichKraft Sendt: 21. oktober 2019 20:33 Til: [email protected]Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Kurt, thanks again for your explanations and pictures. Now I have to experiment for a while and build a suitable fixture and see what the resuts are. I don't want to overdo it too much, primarily I need a good and reasonabe accuracy to compare ferrits for EMC applications of various manufactureres. Once more thanks, and I'm sure at some point of time I will have more questions.... or even results. Always great help to have someone experienced here.
|
Hello Kurt, and others,
I still haven't build a robust fixture, but experimetally taking some measurements on EMC bead, or right now on a wire-wound inductor with a 3mm ferrite core for EMC application.
I was assuming that the results of measuring Z (S11 channel 0) will closely match the results on measuring Gain (S21 channel 1).
So basically I soldered the coil between two SMA connectors and have the SMA cables connected to Ch0 and Ch1.
For some reason the frequencies of max. Impedance S11 Z (Ch0) do not even closely match the frequency of min. S21 Gain (Ch1).
Z on Ch0 shows max. Impedance at around 140 MHZ, but min. gain is around 260 MHz.....
When connecting Ch0 and Ch1 directly the S21 gain looks pretty good (flat at 0db)
What am I doing wrong or let's say, what is my misinterpretation of S11 Z and S21 Gain?
Or is something wrong with the VNA ?
|
Hi Ulrich That is probably easy to explain. When doing the Ch0 S11 measurement I anticipate you are using a female bulkhead/PCB SMA adaptor to which you solder the coil. Then there are two likely errors. First the calibration might be wrong is you calibrate at the end of the test cable using the female female adaptor and the SMA male kit as assumed ideal. If that is the case and removing the female female adaptor for being able to fit the SMA female adaptor with coil your calibration plane is "out in the blue air" as you calibrated at the end of the female female adaptor no longer fitted. If the female adaptor and the SMA female adaptor with the coil has same delay it is just fine but no likely and probably shorter for the coil adaptor so you have a residual capacity shunt to the coil lowering the resonance frequency. If you however used my data for the female calibration kit published when calibration at the end of test cable then the calibration plane would be correct at the SMA male adaptor but now the full capacitance of the coil SMA adaptor will lower the true resonance frequency probably even more. The NanoVNA can pull the calibration plane backward by setting a positive delay and if calibrated with the male cal kti at the end of the female female adaptor and the coil adaptor has a shorter delay than the female female adaptor, then you can tune the delay with the coil adaptor without coil fitted to a phase trace showing 0 degree phase for Ch0. The mount the coil and measure S11 reflection. All in all measuring coil with S11 reflection is very difficult and the only way is to create 3 calibration standards using identical SMA adaptors as the one used for soldering the coil to. These three calibration standard having for the short a 2 mm thick rigid shorting disk, for the open the center conductor grinded down to Teflon surface and the for the load 2x100ohm SMD resistor with the center conductor reduced to 0.mm length. Even then the solder used for the SMD resistor represent a fringe C of some 50 to 100fF incl. the fringe C for the center conductor and the open has a small fringe C of maybe 25-50 fF. It all has effect on the resonance frequency. Well the S21 measurements is far better but the condition for a correct measurement is that the source impedance for Ch0 and the load impedance for Ch1 must be 50 ohm clean, neither the case but still closer to reality. You have still some impact from the two SMA adaptor to which you fit the coil which should be modelled away. A trick is to mount a small 2 way pin socket to the two center conductor of the SMA adaptor and create 3 calibration pin pin adaptor with two 100 ohm SMD resistor for load, for open a pin pin adaptor in open condition and for short a shorted pin pin adaptor. The do a standard Refelction calibration in "S21" serial condition and solder the coil to a fourth pin pin adaptor. The you are done and has compensated all the fringe elements. I am pretty sure the NAnoVNA will work in the special reflection calibration mode I "invented" several years ago. During calibration not calibrate isolation but thru is OK (as far as I remember) I have not tested this with the NanoVNA. Else you can converter the S21 measurement saved as a s1p file to S11 with the formula (3*S21-2)/(S21-2) in a spreadsheet. Remember s1p files are pure txt file and show the S parameter data as real and imag numbers and when the math result is present in the spreadsheet save these two columns as a text file and rename to s1p extension. You must create the header line manually in a text editor That was a long story to a short question ? Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af UlrichKraft Sendt: 3. november 2019 15:15 Til: [email protected]Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Hello Kurt, and others, I still haven't build a robust fixture, but experimetally taking some measurements on EMC bead, or right now on a wire-wound inductor with a 3mm ferrite core for EMC application. I was assuming that the results of measuring Z (S11 channel 0) will closely match the results on measuring Gain (S21 channel 1). So basically I soldered the coil between two SMA connectors and have the SMA cables connected to Ch0 and Ch1. For some reason the frequencies of max. Impedance S11 Z (Ch0) do not even closely match the frequency of min. S21 Gain (Ch1). Z on Ch0 shows max. Impedance at around 140 MHZ, but min. gain is around 260 MHz..... When connecting Ch0 and Ch1 directly the S21 gain looks pretty good (flat at 0db) What am I doing wrong or let's say, what is my misinterpretation of S11 Z and S21 Gain? Or is something wrong with the VNA ?
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Kurt,
Thanks for your detailed explanation.
I will have to read a few times to fully understand the background. But what you said makes sense and I will try to change my calibration process according to your recommendation.
That VNA stuff appears to be more critical to what I was aware of.
I hope my rusty knowledge from university a couple of decades ago will help.....
Thanks again !
?TypeApp for Android herunterladen ?
Am 3. Nov. 2019, 16:51, um 16:51, Kurt Poulsen <kurt@...> schrieb:
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Show quoted text
Hi Ulrich
That is probably easy to explain. When doing the Ch0 S11 measurement I
anticipate you are using a female bulkhead/PCB SMA adaptor to which you
solder the coil. Then there are two likely errors. First the
calibration might be wrong is you calibrate at the end of the test
cable using the female female adaptor and the SMA male kit as assumed
ideal. If that is the case and removing the female female adaptor for
being able to fit the SMA female adaptor with coil your calibration
plane is "out in the blue air" as you calibrated at the end of the
female female adaptor no longer fitted. If the female adaptor and the
SMA female adaptor with the coil has same delay it is just fine but no
likely and probably shorter for the coil adaptor so you have a
residual capacity shunt to the coil lowering the resonance frequency.
If you however used my data for the female calibration kit published
when calibration at the end of test cable then the calibration plane
would be correct at the SMA male adaptor but now the full capacitance
of the coil SMA adaptor will lower the true resonance frequency
probably even more.
The NanoVNA can pull the calibration plane backward by setting a
positive delay and if calibrated with the male cal kti at the end of
the female female adaptor and the coil adaptor has a shorter delay than
the female female adaptor, then you can tune the delay with the coil
adaptor without coil fitted to a phase trace showing 0 degree phase for
Ch0. The mount the coil and measure S11 reflection.
All in all measuring coil with S11 reflection is very difficult and the
only way is to create 3 calibration standards using identical SMA
adaptors as the one used for soldering the coil to. These three
calibration standard having for the short a 2 mm thick rigid shorting
disk, for the open the center conductor grinded down to Teflon surface
and the for the load 2x100ohm SMD resistor with the center conductor
reduced to 0.mm length. Even then the solder used for the SMD resistor
represent a fringe C of some 50 to 100fF incl. the fringe C for the
center conductor and the open has a small fringe C of maybe 25-50 fF.
It all has effect on the resonance frequency.
Well the S21 measurements is far better but the condition for a correct
measurement is that the source impedance for Ch0 and the load impedance
for Ch1 must be 50 ohm clean, neither the case but still closer to
reality. You have still some impact from the two SMA adaptor to which
you fit the coil which should be modelled away. A trick is to mount a
small 2 way pin socket to the two center conductor of the SMA adaptor
and create 3 calibration pin pin adaptor with two 100 ohm SMD resistor
for load, for open a pin pin adaptor in open condition and for short a
shorted pin pin adaptor. The do a standard Refelction calibration in
"S21" serial condition and solder the coil to a fourth pin pin adaptor.
The you are done and has compensated all the fringe elements. I am
pretty sure the NAnoVNA will work in the special reflection calibration
mode I "invented" several years ago. During calibration not calibrate
isolation but thru is OK (as far as I remember) I have not tested this
with the NanoVNA.
Else you can converter the S21 measurement saved as a s1p file to S11
with the formula (3*S21-2)/(S21-2) in a spreadsheet. Remember s1p
files are pure txt file and show the S parameter data as real and imag
numbers and when the math result is present in the spreadsheet save
these two columns as a text file and rename to s1p extension. You must
create the header line manually in a text editor
That was a long story to a short question ?
Kind regards
Kurt
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af
UlrichKraft
Sendt: 3. november 2019 15:15
Til: [email protected]
Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig
Hello Kurt, and others,
I still haven't build a robust fixture, but experimetally taking some
measurements on EMC bead, or right now on a wire-wound inductor with a
3mm ferrite core for EMC application.
I was assuming that the results of measuring Z (S11 channel 0) will
closely match the results on measuring Gain (S21 channel 1).
So basically I soldered the coil between two SMA connectors and have
the SMA cables connected to Ch0 and Ch1.
For some reason the frequencies of max. Impedance S11 Z (Ch0) do not
even closely match the frequency of min. S21 Gain (Ch1).
Z on Ch0 shows max. Impedance at around 140 MHZ, but min. gain is
around 260 MHz.....
When connecting Ch0 and Ch1 directly the S21 gain looks pretty good
(flat at 0db)
What am I doing wrong or let's say, what is my misinterpretation of S11
Z and S21 Gain?
Or is something wrong with the VNA ?
|
Starsekr
Kurt Poulsen
KT7AZ
