Demystifying Cable Antenna - Can Ferrite Increase Emissions?
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- Опубликовано: 11 апр 2022
- In this short video, we showed you that sometimes, when placing a ferrite core on a cable, noise at certain frequency increase. Why is that the case? You will find out!
Excellent explanation. Thank you, Sir!
Nice on-the-fly debugging. Thx for video!
Great explanation. Also, I enjoyed your interview with Feranec that made a cameo in this video, congrats on your work.
That was amazing. Do more of these videos. Thank you
Thanks for giving a super great demo! Did not consider what happens when you have a ferrite only on one side :O
hi Antalife, yes, most of the time, ferrite on the enclosure side will just do the job. This is one of the few occasions where troubles came. I would not demonstrate a normal case coz it is not as interesting as this case.
Move your current probe along the cable and you'll probably see a variety of different signatures. Radiated antenna measurements tell the true story.
Hi Julia, great pleasure here that my humble video gained your attention. Indeed, the problem I was trying to demonstrate came from a radiated emission failure of a client's product(But I cannot use their product for demo for confidential reasons). And as you said, current probe measurement on the cable does not necessarily translate into radiated emissions (simply because of the standing waves and the cable antenna pattern).
Great work Dr Zhang! This is a helpful explanation, I would not have considered the added impedance mismatch.
Thanks Jon. Yes, in the field, we did see a few cases where using ferrite to suppress noise, targeted noise decreased while other noise increased. This is particularly true when f1=2f2, because the same cable length is half wavelength for one and a quarter wavelength for the other.
@@MachOneDesignEMC how the noise level relates if half or quarter wavelength? is that related to impedance of far/near field?
Thanks a lot, great work.
why the first time you put ferrite on the the cable condition got worse? we build a high impedance path for noise, didn't we?
we changed the impedance at one end of the cable, so that cable (same length, same cable) becomes a quarter-wave length antenna
Can ferrite increase SNR when receiving a signal?
If there is common mode current on a cable, then there must be standing waves on the cable. As far as I can tell , you lined the ferrite up where there was maximum current density on the cable. That doesnt tell us which device is the problem. The problem is in the interaction of the components. Please let me know if I am wrong.
Hi You are right. The standing waves will be present on cables. Hence, using RF current probe to predict radiated emission can only be partial, because of the same reason you mentioned. It is therefore recommended to move the RF current probe along the cable to find where the maximum current is and use it as a reference, which is what we did in this demo. Of course, in a real troubleshooting case, I would always have an antenna placed to cross check the performance. I do believe the RF current measurement CAN tell us which device is the problem, especially both devices have a metal enclosure. The key point we are trying to make in this case, is that for a cable antennas to be effective, one would need some impedance difference at the end of the cable
@@MachOneDesignEMC Thanks.. I like your method because at least you can show your boss that its ok to spend another 2500 for chamber time and then not be surprised. Do you use a preamp with your antenna?
@@NE-Explorer Sometimes, I used a LNA (low noise amplifier) between the antenna and the SA, sometimes not.
Hi! There is a large portion of people in the E-Sports world of gaming who seems to suffer from rather unusual stuff with Emi/RF/EMF.
Would you mind joining our discord to try helpout our current situation?
There is a bunch of research already done but no one is working in EMC industry so it would be extremely helpful to get your input for our research.
Hi Jörgen, that is a very valid point. I am not a gamer, but i understand that one would need to assemble a high performance PC and this newly assembled PC perhaps never goes through the compliance EMC tests. That is a conern, isn't it!
I am willing to give you some help. Please contact me through email. you should be able find my email address on our website.
how do the "suffer" from it?