Transmission Lines : part 2 | Let's take a journey with the signal inside the transmission line
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- čas přidán 30. 09. 2022
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Amazing video! I am at the moment studying telecommunications and although I had a loose idea what these concepts meant I never had such intuitive understanding that your videos provide. Also did you mean to show the Zo at 11:49 as 50 ohms? Shouldn't it be 80 or am I missing something?
yes, it should be zl=80. Here the source finally see the 80 ohms load impedance.
thank you:)
one of the best videos i have seen which explains the reflections of power signals in transmission lines.
This is the clearest explanation I've seen of this topic - thanks for taking the time to make it!
i wish i had these videos during my EE course
teachers doing on boards and replicating with real components in the lab was so hard
As a professional antenna engineer, I feel like I finally understand the mechanism of reflections instead of just memorizing this process. Thank you for the amazing video!
Congratulations! You can now call yourself a real engineer, and not only someone who has a master in engineering ;-)
But i didn't understand. How is there conductance between wires in parallel?
@@sagarrawat7203 If you consider the resistance of the wire insulation and the medium (seawater, air, etc), you can model it as an extremely large resistor. In almost all cases, it's so high that it can be treated as an open circuit. However, when dealing with extremely high voltages, the small amount of current that flows through this large resistance is not negligible in the case of per-unit-length circuits. So there is some resistance in parallel (shunt resistance), and therefore there is a conductance which is 1/R.
@@Blank-wv3uf thanks. But, then why shouldn't we take resistance R in parallel too than conductance G? This G made it complex. Is G really different?
This is gold! I really love the duality of the transmission problem from plenty’s pow. When I’ve studied it, the concept that really helped me to get to the point was the fact that nothing could travel faster than c, so the generator’s voltage phasor is actually a signal. Therefore this “signal” needs time to arrive to the end. But this visualisation had a lack on the reflections because it is not so immediate to immagine it from the signal pow. However this visualisation of the continuously correction of the capacitor’s voltage is brilliant.
This is wonderful, all the best!!
Fantastic! most intuitive explanation so far
Amazing content and a beautiful explanation!
An extremely helpful video.
Thank you
Daniel
Beautiful!
Thank you 😍❤️
Really nice illustration. I think until you appreciate the finite propagation speed of the signal, none of this transmission line stuff makes sense, but of course,it’s still really really fast, so hard to have much intuition. Your video really helps visualize the reflection due to impedance mismatch - why is there a reflected wave? Because it takes time for the input signal to reach the load! I’ve taken the coursework, understood the math, but never really understood the physics of it all until your video. Thanks!
Great video! Things become more and more clear. What I still do not get right in electricity is active and reactive power propagation.
Amazing video
Great video hours of effort put in
Great series ... I look forward to scoping your other videos. Thanks. Subscibed. Cheers ...
Nice man it helps
Amazing!
thankkkkkk you very much
Excellent video. Can you point usto the simulation software you used in this video. Thanks. Keep them coming.
Here I used keysight advanced design system (ads)
Thanks! Great video👍, but there’s one thing that I’m not sure. How do we choose appropriate capacitance and inductance when modeling the transmission line?
I think we don't insert any capacitor and inductor in wire. 🤔not it's only wire?
Hey, excellent video !!!
I just wanted to ask that in the case where load impedance matches characteristic impedance( @8:50), is the output voltage level necessary 0 before the traveling wave gets to the load? I have seen a video of veritasium in which he says that there exists a minor voltage even before the wave reaches the load.
P.S. I can give the link of the video of veritasium if you want.
Thanking you in anticipation of your respnse.
can you the veitasium link please.
@@somenmohanty9557 czcams.com/video/oI_X2cMHNe0/video.html
Arround @18:59
I will make a video soon replying to Veritasium. I think he was wrong. thank you for highlighting that point
@@TheSiGuyEN thank you so much for replying!
Eagerly waiting for your video!
this video is so amazing but I want to ask a question that if we cut the transmission of the signal after some time, the long wire is storing the charge. In lossless line how to discharge them or will they form an oscillation or not? please reply I am eagerly waiting.
The stored power will be discharged into the load
I have a question here, In the unmatched load condition, is it still correct to replace the rest of the line by the charecteristic impledence like we've done in ech of the individual "sections"
yes, as long as the signal is still travelling toward the load before reaching it. Before reaching the load, the signal doesn't know what kind of termination; it sees only the charecteristic impledence of the line.
Great video! Very clear explanation.
Why is the voltage on the 80 ohm charge not going to 320mV first? If we have the same current (4mA), the voltage on the load should be 80ohm*4mA = 320mA. What am I missing ? :D
which minute?
9:42 "same current (previously 4mA) driving higher resistance (now 80ohm) gives us higher voltage, 245mV" @@TheSiGuyEN
The forward current is the same 4mA, but 80ohm has backward (reflected) current, so total current is less than 4mA.
if you see the graph at @9:48 it effectively reaches 0.32V (look at the spike voltage). But then if you calculate the reflection coefficient gammaL(80-50)/(80+50) and you multiply it for 0.2 you get 0.245 that is the reflected voltage. So the difference is 0.45V.
Hello sir, im not quite understanding the whole concept of the video and i want to ask whats the point of examining this phenomena ? What does it do in our daily power transmission ? Does power reflect from my home back to the station ? Also if i see the generator voltage and my appliance voltage at the same synchronized clock frame, will it have a phase difference due to the signal delay ? We say power grid is in sync, but after watching those transmission line videos im in doubt. Please answer sir ty
Hope my newly uploaded video answered your questions
What a simplified lecture ╰(*°▽°*)╯
You have a deep understanding of phenomenas, this not so easy for me. I have a question : From 0 to 5ps, this is the time of the capacito charge, then before the voltage is established , I see some ripples, they are do to what? And is there a possibility that thse capacitances filter HF? also there is a condition about distance between the 2 conductors to assume a TL, physically that correspond to what? On youtube we could see that all intresting scientific videos are in english, unfortunatly in french we dont. Also I had courses on TL and never the teacher talked about all of what you are explaining. THANKS a lot for these precious videos, even I dont get it all but I get some very precious informations.
"I see some ripples, they are do to what?" there're ripples because the circuit is not first order. The approximation at 4:00 is first order rc circuit, but this is very accurate. There are inductors and they should be taken into consideration for more accurate results.
"And is there a possibility that thse capacitances filter HF?" They do filter HF. we applied a step voltage at the input, and the voltage at each section is low pass filtered as shown in the video.
Also the overall response of the TL is sort of low pass filter response 13:14 (you apply step at the input and the output will settle after some amount of time govern by reflections as well as lp filteration associated with the capacitors)
"there is a condition about distance between the 2 conductors to assume a TL, physically that correspond to what?" No, the only condition to assume a wire as a TL is that the length of the wire is much larger than the wavelength of the signal. the traces on PCB for example are considered TLs if the circuit work at high frequencies (wavelength is small).
The distance between the two conductors actually affects the capacitance per unit length, and inductance per unit length which in turn would affect the value of the characteristic impedance and propagation constant (they depend on the capacitance and inductance per unit length).
You can easily predict the effect of the change of the value of c, l, and zo (same graphs as shown in this video but with different values).
If you have any other questions or recommendations, please don't hesitate to ask :)
@@TheSiGuyEN thank you, I'm so glad to read you, your answers are very précious. I look for courses to understand deeply EM. Dovyou have références.thanks à lot
@@karielf8947 it depends on your background and what you want to learn. But in general, this is a good book:
"Microwave Engineering by David M. Pozar"
@@TheSiGuyEN thanks à lot. I m à phd in emc, and I use EM in my analysis. I need to predict what could happen, or to analyse measurements or analysis.
@@karielf8947 Great, Here're some of my favourite books:
Engineering Electromagnetics. By John A. Buck, William H. Hayt
Electromagnetics: With Applications By
John D. Kraus, Daniel A. Fleisch
Field and Wave Electromagnetics By
David Keun Cheng
This is a great course covering fundamentals of electricity and magnetism By Prof Walter Lewin:
"8.02x - MIT Physics II: Electricity and Magnetism"
czcams.com/play/PLyQSN7X0ro2314mKyUiOILaOC2hk6Pc3j.html
you can use this course to refresh your memory about the basic concepts but as an engineer, don't rely entirely on it.
I simulated thé circuit minute 4.32 on PSpice, I used DC crurent power, c 20fF, and R 50 Ohm. All crurent pass by thé resistor, thé capacitor does not charge anymore.dont know why.
you can upload a screenshot of your schematic as well as the results besides your question on the Discord server or the Reddit community (links are in the description) so that I can see where is the problem
@@TheSiGuyEN ok thanks I will try. What I see is that PSpice does not show thé transient state only thé établished state. Thé time scale is good. I should see thé curve Vc=E(1-exp(-t/to).
I just got thé answer, I had to défine initial conditions of the capacitor to 0. To indicate that thé capacitor is discharged. Youpi!!
czcams.com/video/EEP2UPVIm9o/video.html
Very good video to understand the reflections on transmission line . This is the basis and fundamental for SI analysis.