Transmission Lines: Part 1 An Introduction
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- Опубликовано: 23 авг 2022
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You just explained better than my professor at the university. I couldn't understand from the books and lectures, but after watching your video, I am just wondering, how it is possible to teach like your video! Thank you man, you made my day!
Studying this for my electrical engineering lab course, getting the visual intuition is great!
This is the 4th or 5th video on your channel I watched. Your explanations are great, straight to the point!
Always awesome to see new youtubers in the RF/EM field! Keep it up :)
sure :)
How much did RUclips pay you?
Excellent!! visualizations. I had always struggled with EM Theory and this makes me want to learn more now. I was not clear on what the characteristic impedance was.
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what a wonderful explanation and a impressive understanding !
Your presentation style is top notch, sir! Very nice! And you seem very knowledgeable. I'm just an electronics tech, but I'm supposed to understand the basic stuff, I figure. A voltage waveform makes perfect sense to me, but not a current waveform; they don't seem like different things to me. Voltage makes current flow, so the current accompanies the voltage like a side-effect, when the circuit is closed; they are inseparable. I figure I must be wrong, but I don't see where. We were taught that "drift current" is not electric current, this latter transacting at near-light speeds, whereas drift current might take an hour to travel an inch. It is current flow that engenders "resistance"; voltage, or charge, doesn't encounter the same sort of resistance. But it makes intuitive sense for me to imagine that it's this drift current that is organized and motivated by the voltage differential to become electric current flow in a complete circuit.
EXCELENT! REally you solve an old problem that I had, and no one could answer me, THANKS THANKS THANKS
DUDE! You make some AWESOME content! Thank you! I shared this with a whole BUNCH of Amateur Radio friends!
Amazing explanations! The best I've seen so far
It makes my day to hear that :)
the feedback loop at the end is dope!
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Excellent!
Explained the concept in a great way 👍. And l like the feedback network in the end
my pleasure
Neat stuff, keep it going
thanks
Thank you
Thank you.
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I wish you'd explained the meaning of the characteristic impedance. You put a formula, but didn't give the definition or explain what it means.
From how i understand it:
The characteristic impedance of a line is the resistance when placed and replaces the line will result in no reflection. Its defined as impedance because the "characteristic impedance" is only applicable to AC / waves. it arises from the construction of the line: from the capacitance to itself and from the inductance through. Because we live in a non ideal world, a single copper wire will have inductance. Two copper wires will have capacitance. Interestingly, we find the length of the transmission line is proportional to capacitance and inductance. Similar to density. A blovk of aluminum has X, Y, Z dimensions. We increase X by some small amount x, the mass will increase by x times Y times Z times density. We have a transmission line with capacitance "density" and inductance "density". When we turn the circuit on, the electric field travels very quickly. The electrons take time to move, and when they move they update their field and move other electrons (inductance). The electric field that moved very quickly affects electrons, pulling them to the other line (capacitance). Electrons are both pushing eachother and propagating a wave. At the Same time, pushing to the edge of the conductor and showing the results of a wave. Electron movement in the inductive case is "lagging" behind the electric field (its like inertia, you push a skater, the start is slow but later they are gliding without your pushing). Electron movement in the capactive case is "leading" (because the more the electrons push to the surface, they start to slow down other electrons). Remember how i said reflection - when you work with these capacitances and inductances, tou get waves/propagation. Because it is a combination of electric field and electron flow, you find there is an impedance. A reflection occurs because you supply an electric field and the line (its indutance and capacitance) determine electron flow in a propagating manner. When the line has a change in impedance (inductance or capacitance), the electron flow inherently changes. The change means it has to propagate, it propagates forward in a different manner to before (if electrons were shoving eachother before, now its like a light tap), AND it propagates backwards (equal and opposite reaction). Its behavior is identical to a wave hitting something and reflecting back. In a DC case, the line impedance means nothing. In AC or transient (connecting a switch for instance), the line impedance matters.
The reason that the resistance replacement does not cause a reflection is because characteristic impedance is defined as a single wave without reflections and is the ratio between the voltage and current. A resistor is inherently defined as a ratio between those two values. As such, the wave travels through and "sees" a resistance. Because its AC/transient, we say impedance to note that it is not static - it is periodic. because reflections happen for waves/transients, and because they happen when impedances change, replacing the line with a resistor means the electric field and electron wave will not see a change in impedance.
The line is not a resistor though, it is 2 lines that are meant to form a loop with some other thing. If there is no connection, there is a reflection. If the thing has a different impedance than the line, then there will be a reflection. If the thing has the same impedance, there is no reflection. And these are only true for AC/transient. In the DC case, there is no reflection.
Listen again starting at 5:00 in. It’s abstract in a way, but clearly explained.
Dude, this is insanely good, I was searching for such quality content for my Radio Frequency Course for 2-3 months. The 3b1b style of thumbnail made me click this. Thanks a ton !! Really helps ❤.
The lack of emphasise on conceptual depth in my college makes we wanna kill myself sometimes...
By the way, what softwares did you use to make this ?
manim. A community-maintained Python library originally created by grant sanderson (3blue1brown) for creating mathematical animations.
Great video. Keep it up
thank you
Sir, could the abbreviations or legends be updated referring to formula at the gamma. Elaboration on the single line with inductor and resistor having two parallel line where one of it was capacitor and the other is resistor on sine wave with actual numbers and maths calculating the impedence and the voltage at the start and end including the flow? If resistor on single line is higher it push back current and vote backwards flowing through to capacitor. How much is the limit on impedence or reverse current that can be stored in capacitor and what is the voltage and current within the single line inductor and resistor and capacitor with resistor circuit. (Thank you, this information helped on maths excellently)
So how much would be the wavelength of the signal in the transmission line?
I have a question, since electricity travels at light speed, we can see difference in the voltage levels after the distance of 3000km, does any transmission has the distance more than 3000km? Please help to understand!!!?
why the bottom wire has no inductance and resistance
Dont know how you get the formula of input impedance
ABCD parameters matrix multiplication
at 3.48 isnt it the opposite ? At low frequency an inductor reduces to a short and a capacitor to an open circuit
Huge capacitance has very small impedance even at low frequencies (Zc=1/jwc) where w=2.pi.f
Also huge inductance has very high impedance even at low frequencies Zl= jwL
the inductance and capacitance here (for this very very long wire) is very very huge
3:45 why would shunt capacitance become short circuit?
Huge capacitance has very small impedance even at low frequencies (Zc=1/jwc) where w=2.pi.f
Also huge inductance has very high impedance even at low frequencies Zl= jwL
🙏🙏🌹🌹🌹🌹
but when you talk about lumped circuit in low frequencies, why you say that inductance is equivalent to Open C, and capacitor to short C, is it not the inverse?
The total inductance and capacitance of this very long wire (5585 km) is huge.
Impedance of that huge inductance (j.2pi.f.l) is very large even at low frequencies (f) so it would act as an open circuit.
At the same time, impedance of that huge capacitance ( 1/(j.2pi.f.c) ) is very small so it would act as a short circuit.
Notice that this is an AC circuit not DC :)
@@TheSiGuyEN Thanks for your answer
Have we not taken into account the mutual inductance?
mutual inductance of what?
@TheSiGuyEN I apologize. I mistakenly thought that external inductance was mutual inductance. sorry 🙏
Is transmission line theory for AC currents?
I assume it must be, because we talk about frequencies.
Yes, but even many non-AC circuit situations manifest AC characteristics during state changes. Digital signals involve state changes that are essentially impulses or ramps that have AC characteristics. So transmission line analysis can apply even in highly integrated DC circuits.
@ 00:09 "SUPPOSE WE HAVE TWO LONG WIRES" (with one wire you suggest this is made up of the two lines drawn).
@ 01:01 ARE YOU TALKING ABOUT VOLTAGE-DIFFERENCES ALONG THE LINE OR BETWEEN THE TWO LINES???
Advice: Be more clear in the terminology you use!
3:41 Something must have been mixed up 🤔
Yes, the cap should be open and inductor should be shorted
Huge capacitance has very small impedance even at low frequencies (Zc=1/jwc) where w=2.pi.f
Also huge inductance has very high impedance even at low frequencies Zl= jwL
IMO, skips all the important parts... especially the math.
Yes, that’s commonplace in an introduction…
Finally someone like @3blue1brown in Electrical engineering
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