but if someone says that the referred paper is reliable to describe RF signals and to give pcb guidelines, then he is wrong because the paper is covering signals up to 1GHz, which are a low side of the RF spectrum and the easy part… in my experience signals up to 1GHz are just referred as high speed signals…
I’m not saying that Ti engineers are writing their guidelines without scientific data as someone else in the thread… the opposite!
I just said:
you can easily test your signal loss from the in/out path without the need to measure any EMC radiation at all…
so your model could even not exists, but your data can be scientific anyway…
If you can reach your professor, I would be glad to have an academic point of view in this post referred to signal from 1GHz up to hundreds…
but stop pulling me in this thread… as I already stated out I don’t like to be in anymore …
arcs are almost a must for flat-flex boards. Because sharp concave corners create stress concentrations, making a perfect starting point for fatigue cracks. Sure, 45 degree turn is much better than 90 degree turn, but it does not eliminate the problem.
arcs are very desirable in high voltage boards. There, sharp convex corners are places where corona discharge is likely. Not only does it reduce the breakdown voltage, it can be a long-term reliability problem. If there is a subtle corona discharge, it causes insulator degradation nearby, which can lead to carbonized short after a long period of time. Similar to what happens in this video: https://youtu.be/QRHNZaVLSh4
No? It’s already well established that vias create signal integrity problems for signals in the GHz range. Vias being worse than right angle bends doesn’t mean right angle bends aren’t a problem also.
The thing that gets me is that a HUGE number of high speed dev boards out there, from ADCs to DACs to comparators to flip flops, from every manufacturer, use rounded traces. So either rounded traces are a myth and the hardware designers from every major IC manufacturer in the industry have bought into the lie, or there’s something to it. Either way, I don’t understand why there’s this resistance to add that functionality to KiCad. It can’t hurt.
Hmm, adding code always creates new bugs, more complexity for users and developers. It’s always a question of cost/benefits, economics applies to free software as well. If you look at the other 350 or so feature requests, which features are more or less important? Everyone will have their own view.
There is a sort of voting system, if you click “also affects me” it adds to the bug “heat” index. If we sort by that we get most popular wishlist requests
The top one is teardrops. Curved tracks is not very high, but in the top 75. However, there is not much relation to the popularity and what gets implemented, that depends on whether it’s an itch developers also wish to scratch.
[quote=“suicidaleggroll, post:34, topic:658”]
The thing that gets me is that a HUGE number of high speed dev boards out there, from ADCs to DACs to comparators to flip flops, from every manufacturer, use rounded traces. So either rounded traces are a myth and the hardware designers from every major IC manufacturer in the industry have bought into the lie, or there’s something to it. Either way, I don’t understand why there’s this resistance to add that functionality to KiCad. It can’t hurt.
[/quote]I remember reading, pre-internet, about some researchers coaxing single electrons down traces. That had to be curved ‘like sine waves’. I’ve searched and can find no reference to this research now. It may have been debunked or it could be I’m old enough to remember anything I want, factual or not.
It does make me wonder if pushing certain speed and boundary sizes will make this kind of thing necessary.
In school we learned electric fields are stronger at sharp turns. The way to look at it is the perpendicular lines of force get closer together. There is a reason spark generators have pointed ends. Also lightning rods a are pointed for similar reason.
Who said anything about radiation? Electric fields are what determines capacitance Capacitance affects transmission line speed and impedance. Adding trace delay has curves for a reason. Not to look pretty.
That’s a tautological argument, people use curved traces because they think it is important. That only proves people generally follow the herd, it is not proof of any measureable effect.
The reason why this feature is not in kicad is not because it is unnecessary in general but because nobody bothered to create a mergeable patch that adds this functionality.
Currently kicad is not particularly well suited for high frequency design. (From reading the forum i get the feeling that there are a lot of missing or half added features. Maybe a this will be better in v5 but i guess some things might still be missing in it.)
Using “free angle mode” routing in OpenGL I made this. My mind cannot handle seeing RF traces with angles even though I’m fully convinced it doesn’t matter. If you want, you can measure up the turning points in your trace using drawing elements for visual help while routing. If you need this exact same trace again you can simply copy it and assign it a new net.
I am guessing that curved traces started with crepe tape or ink resist pen designs.
It would be an interesting experiment with a field solver to see how high frequencies have to be for corners to show
Going in circles? All I can say is that we called schematics lumped models. When you get into higher frequencies you need a distributed model. Capacitor coupling do to electric fields causes cross talk to adjacent traces. Adding trace delay tuning and differential pairs is needed so I guessed someone knows the problems. As far as measuring, sometimes you get flaky errors that are hard to measure.
The frequent regurgitation of this topic often requires that you just let people believe what they want to believe as it seems no amount of empirical evidence, or even common sense, is going to convince them otherwise. But it is also quite comical to read the various explanations for why we should avoid right angle corners. This time around they’ve included comparisons to spark gaps and lightning rods, causing plasma and corona, and some new form of capacitor created by electric fields. Not to mention the single electron travelling along a sinusoidal trace. And don’t ask me what lumped and distributed models have to do with any of this.
This topic clearly highlights the vast misconceptions surrounding not only electricity in general but also the propagation of signals through conductors such as on a PCB. The only credible reason given above for avoiding right angle corners is the mention of mechanical stress in flex PCBs. Some people still seem to have this image of electrons racing down a track and trying to negotiate a right angle corner at near the speed of light, some of them fail, hit the edge of the track and bounce back. Imagine their surprise when they learn that, although the signal might propagate at near the speed of light, not only is the velocity of the electrons themselves quite slow (relatively speaking), but they barely move at all, orders of magnitude less than a millimeter (at 500MHz).
That’s not to say that right angle corners never cause any problems but when they do, two 45 degree corners are almost always sufficient. It stands to reason that rounded corners therefore must be even better, and they probably are, but not likely enough to make any difference in most cases.
Cold winter, so let’s throw a log into the fire…
I’d love to have at hand one of the books mentioned on the first slides of this presentation
as I suspect they would explain somewhere the gory details of drawings on page 47 (slide 93)…
I won’t try explaining them myself, as I’m just a humble lumberjack
All I can say is that we called schematics lumped models. When you get into higher frequencies you need a distributed model. Capacitor coupling do to electric fields causes cross talk to adjacent traces. Adding trace delay tuning and differential pairs is needed so I guessed someone knows the problems. As far as measuring, sometimes you get flaky errors that are hard to measure.