The reason I refer to the speed of light is because all signals on a PCB are propagating electromagnetic waves, and all electromagnetic waves travel at the speed of light. The speed of a signal on a PCB is equal to the speed of light in the dielectric (for striplines), or it is the speed of light as determined through a dispersion relation at the air-dielectric interface (for microstrips).
Thank you for your leture. Is there a way to make stub vias or stub traces useful as equalizer? For instace, shorting the open end of the stub to ground.
If your goal is to use a via stub as a transmission line stub then yes it will act like that but it will only serve that function at very high frequencies, like into long-range radar bands. This is due to the typically very short size of via stubs. Also the stubs will only provide that type of action over a narrow bandwidth. So if you are only working at a single frequency or very narrow bandwidth (about 3% of the carrier frequency), then you would have the desired stub effect.
@@Zachariah-Peterson Thank you for your reply. I am not familir with frequency range. What do you mean by "it will only serve that function at very high frequencies?" Is the transmission line with the data rate of 10Gbps considered as very high frequency or very high bandwidth?
As far as I know, backdrilling can cause reliability and manufacturing issues and is really expensive. I think backdrilling should only be considered after evaluating HDI as an option. Please correct me if I'm wrong.
Yes it is expensive, also sometimes you might not need it. If you're not doing blind/buried you can always use thin laminates on surface layers are route into those instead of routing into the middle of the board and you'll have a smaller stub. I'm not aware of anything surrounding hole wall reliability, but there is a reliability challenge from increased clearances required to completely backdrill that hole. If there is misregistration or wander the drill could cut into nearby copper if the clearances are too tight.
Please more videos on how to use Altium designer in some aspect. There are endless teaching videos on all this high speed digital stuff. Try something different to distinguish your content.
Please make a video series on eye diagram.
Awesome, can you do some info on microvias.
Just curious about your use of speed of light C instead of speed of signal on the PCB material in your calculation.
The reason I refer to the speed of light is because all signals on a PCB are propagating electromagnetic waves, and all electromagnetic waves travel at the speed of light. The speed of a signal on a PCB is equal to the speed of light in the dielectric (for striplines), or it is the speed of light as determined through a dispersion relation at the air-dielectric interface (for microstrips).
Thank you for your leture. Is there a way to make stub vias or stub traces useful as equalizer? For instace, shorting the open end of the stub to ground.
If your goal is to use a via stub as a transmission line stub then yes it will act like that but it will only serve that function at very high frequencies, like into long-range radar bands. This is due to the typically very short size of via stubs. Also the stubs will only provide that type of action over a narrow bandwidth. So if you are only working at a single frequency or very narrow bandwidth (about 3% of the carrier frequency), then you would have the desired stub effect.
@@Zachariah-Peterson Thank you for your reply. I am not familir with frequency range. What do you mean by "it will only serve that function at very high frequencies?" Is the transmission line with the data rate of 10Gbps considered as very high frequency or very high bandwidth?
@masa mizuno I created a video about this and it is in editing, it will be ready in a couple weeks.
@@Zachariah-Peterson Thank you. I am looking forward to your video.
As far as I know, backdrilling can cause reliability and manufacturing issues and is really expensive. I think backdrilling should only be considered after evaluating HDI as an option.
Please correct me if I'm wrong.
Yes it is expensive, also sometimes you might not need it. If you're not doing blind/buried you can always use thin laminates on surface layers are route into those instead of routing into the middle of the board and you'll have a smaller stub. I'm not aware of anything surrounding hole wall reliability, but there is a reliability challenge from increased clearances required to completely backdrill that hole. If there is misregistration or wander the drill could cut into nearby copper if the clearances are too tight.
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Please more videos on how to use Altium designer in some aspect. There are endless teaching videos on all this high speed digital stuff. Try something different to distinguish your content.