I've been trying to understand the principle of trace impedance (single ended and differential) for a while, read several articles (all the best google has to offer), but I have still some serious issues finalizing my understanding of it.
First of all, all this talk of fields around conductors made perfect sense for me, completely understandable on intuitive level in terms of where fields come from and what things affect it (trace width, distance to ground path etc.), no problem understanding physics principles behind it there (trace as inductors, resistors and capacitors - totally reasonable).
The problem starts when I hear the word "ohm" when talking about this impedance.
Pardon my ignorance, but when I hear the word "ohm", I understand it as resistance (or impedance) between two points when there is voltage applied to them. So if I see "the trace has 50 ohm impedance", I just don't understand it. To me, "50 ohm" means that if I apply 1 V (DC or some specific frequency or something), I will have 20 mA current.
I understand all the talk about the fields, but I fail to connect this understanding of how fields interact to the word "ohm". For now, it looks like measuring length with kilograms to me.
While writing this question, I was proposed by ee stackexchange to take a look at this: questions similar to what I have on ee stackexchange answered
And it did answer some questions (most of them, actually, such as why the trace impedance characteristic is frequency-independent), so if I get it right, these "ohms" are simply a trace geometry characteristic and have nothing to do with actual voltage and current in the circuits (no 20 mA current when I apply 1 volt?). Then why are they even called Ohms...(rhetorical question, I do realize it's just a final unit that comes out after mathematical operations no matter how counterintuitive for understanding it is).
So, if anyone could confirm or debunk my way of understanding trace impedance as something that has nothing to do with volts over amps and is just a geometrical characteristic (basically, "ohms that are not really ohms?"), I would be very glad.
I would be even more grateful if anyone had any good article or a book chapter that covers exactly that, preferably something that explained this to you personally; maybe it will help me to wrap up my understanding of it. I feel like I kinda get it, but I need some final "aha, now I get it!", and it's best when someone with knowledge answers it, I don't trust my own interpretation of things without anyone's confirmation on this matter.