Gaps In Return Planes
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- เผยแพร่เมื่อ 22 ก.พ. 2024
- Many designers misunderstand how digital signals propagate in PC boards. These digital signals propagate as electromagnetic (EM) waves in the dielectric space between the microstrip trace and adjacent return plane. If this return plane has inadvertent gaps or slots, the return currents are disrupted and the EM wave can leak throughout the dielectric space of the board. This leakage can cause cross coupling between signals and board radiation.
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I have never seen this stuff so well explained. Usually it’s just explained as magic and people wave their hands. You clearly understand what is going on. When you routed around the gap and showed where the current was going my mind was blown.
Wow, this is how electronic engineering should be taught
And this happens already in MHz range.. There are some GHz designs out there, where the return path under the clock is interfered with other traces and power planes (so not technically a gap). I myself did also some 200MHz traces on a PCB, where the GND underneath wasn't so clean and had a big issue with crosstalk and radiated emissions. Very nice demonstration, thank you :)
Thank you for this demo! It's really comprehensive while still being simple and easy to understand.
Wow. I didn't know that. And the demo really hammers the point home!
This is an excellent demonstration, great job!
Ken, this is a great demo. I'll be showing this to all of the people that ask me about high speed design.
Excellent video!!! I love the use of current probes to demonstrate the radiated energy. Thank you for this.
The energy is in the fields, very good demonstration.
Well, this was great! Thank you for your videos, this is extremely useful for me, as I'm investigating ultra low noise techniques for an upcoming project.
Very interesting video. Can you share more information about the 10 MHz harmonic comb generator? It looks like a small handy tool for RF testing.
Really great demonstration! I can't wait to see more.
Excellent video! The best way to understand this material is to do it or watch someone do it. Thank you very much for making this video and focusing so well on the topic at hand.
Use a VNWA as well, get one if you don’t have one. Mine did cost 280€ and reaches 4,6 GHz
Very well explained the need of Uniform Ref Plane, hope more this type of demonstration vedios will come.
Great demo. Would be curious to see common mode currents explained in more detail
Awesome presentation. Could kind of use a secondary audio channel where a CTF programmer is trying to perform time slip attacks (shout outs to Dr. Amy H. Sturgis via Starship Sofa via Podcast Addict,) on low level comms or Vacuum 11.
Thanks for the detailed demonstration.
We may use a massive gnd plane and heavy Rf shield for any circuits to easyli call or work correct.
It allways had an antenna or loop somewhere, or at some point needed to slove the low inductance/high current phats/return phats.
So its like a esential thing to know and not only for an RF guy.
Indeed :)
Great knowledge. Thanks for good and detailed teaching
At 2:26, you can see the analyzer pick up emissions when the gapped line is plugged in.
Now if you could bridge that gap with a two wire links, one each side of the wire, it will be interesting to see how much performance is recovered.
We should have luck parity simulating bridging through vias, etc. (Fun acid test for the pSpice or MLSpice at hand?)
Nice demonstration!
Please make more videos! They’re great : )
This is exactly what we run into sometimes with noisy LED lighting. I wonder if there are any good ways to suppress this RFI when ferrite is ineffective.
I would have thought that if ferrites are ineffective, it is either not radiated emissions or the ferrites are the wrong mix / wrong configuration.
The problem with magnetics is that whenever you think you know the subject, there are 10 more variables to accoiunt for, with each variable having 100 variables of its own.
The math gets deep pretty fast, and one second you are just wanting to throw a balun together, the next you are conducting a PHD thesis.
@@digitalradiohacker Thanks for the thumbs up. It's so good to feel the love coming through my screen!
The first step to fixing noisy LED lighting is buying well-designed products. Unfortunately that’s tough to do without a whole lot of testing!
When you’re to the “maybe a ferrite will fix it” stage, you’re already losing the game.
Really interesting video. Thanks for sharing.
Thanks Ken!
Nice clear video, thank you very much 😃
Excellent!
great video, thanks for it!
would like to see more of these videos
neat!
With a 3D printer frame and the equipment hooked up to a computer, one can script a scan across the PCB and visualize the H field in 3D space. Wish I had one to hack it.
Lol regular free AI modeling ask?