Problems on CTFT/ FT - Part -1

This video deals with finding CTFT of a continuous time signal and plotting the Magnitude and Phase spectrum for some cases. It also helps to understand how to use the properties of CTFT to find the Fourier Transform of signals in time domain.

[@priyankams62]

your approach to analyze and explain the problems is great. Thank you for making it easy.

[@vaniv81]

Very good ...recommended for all ECE students

[@SunilKumar-eo3lp]

Sir, too good. Good one sir. Helping me a lot. Thank you sir. Indebted 🙏🏻👌🏻

[@archanapanigrahi348]

I wish we could have a teacher like u,coz we are still afraid of this subject. Thank u so much sir

[@tilaksrraghunath5774]

it's helpful for mechanical students as well . Vibration analysis requires Fourier transform .

[@vaishnavrengan1286]

Very good lecture !! U made things easy for me. THANKS A LOT! 😊

[@marklee1194]

Thank you sir. Plotting magnitude and phase spectra was not thoroughly covered in class when I took Signals and Systems 1. At least everything is clearer now.

[@techjunkiejdb5476]

That's great 😊

[@shethnisarg3049]

Sir in the last problem 7, if we differentiate on both the sides and then take the fourier transform as we did in problem 6 then we will get fourier transform of u(t) as 1/jw and the pi*delta(w) term is missing .. why we are getting two different answers with two different methods?

[@aykut1]

Yes I need a answer for this (I found answer, answer ise because of dc value)

[@malavikadborkar6209]

Omg !!Even I understood the problem 👌

[@raniwaghmode5239]

This video is very useful to me and sir your teaching style is very nice .but video is not clear to see what you wrote on the board.

[@techjunkiejdb5476]

rani waghmode try to view it in HD mode. 😊

[@seshasankar1892]

i thought it will not get into my mind, when my lecturer took this concept finally i got it because of you sir , thank you so much!!! is there such videos for sequential circuits also in digital circuits and system course ?

[@techjunkiejdb5476]

I have not done yet . I'll do it soon .

[@seshasankar1892]

ok sir thank you so much!

[@limweihan2185]

very good teaching but why did not fixed you camera? ??

[@techjunkiejdb5476]

I have fixed in the next of the videos

[@shivaprasadnayak9186]

Good one👍

[@rashmikumari3863]

How to remember all Fourier formulas ? Any tips or tricks coz sometimes it is integration sometimes summation. Even the ranges are different

[@techjunkiejdb5476]

Rashmi Kumari there are only 4 formulae . Two for Fourier series and two for Fourier transform. Please check my introduction videos on frequency domain representation. For discrete time signals we have summation and for continuous time signal we have integration 😊

[@vnnchetana]

Sir In problem 6 can we directly take sig(x) = 1 for t>0 -1 for t

[@techjunkiejdb5476]

Since there is discontinuity at t=0 . We can’t directly integrate

[@THUNDER-kw3wq]

Sir why cant we solve the last ques by directly differentiating it like we did in the previous question

[@techjunkiejdb5476]

You can’t differentiate u(t) directly . Need to represent it in terms of standard functions and then take its transform . If u differentiate directly and use the differentiation property you won’t be getting the residual term which we get here .

[@THUNDER-kw3wq]

@@techjunkiejdb5476 ohhh but why so?

[@akashjagtap2784]

Sir Why cant we apply differenciation property while solving FT of u(t) signal?

[@techjunkiejdb5476]

Yes we can use. I have made a mistake here.

[@rudreshpandey9006]

sir can u please tell what is the ft of rect function? I am not able to find that.

[@techjunkiejdb5476]

It exists from -1 to 1 with an amplitude of 1 . So just integrate

[@techjunkiejdb5476]

It's sinc function

[@ullalind6137]

Why can't we use the same principle from problem 6. in problem 7. mathematically (since the result is different)?

[@techjunkiejdb5476]

I have used the same principal of equation of sgn(t) . 😊

[@ullalind6137]

@@techjunkiejdb5476 Thank you!

[@musaahmad1097]

Sir for problem 5 is it possible to write x(t) =1 as sgn(t) +u(-t) and plug into analysis eqn and just alter the integral limits?

[@techjunkiejdb5476]

Your addition of two signals will fetch you u(t).

[@musaahmad1097]

I meant to write 2*u(-t)

[@muhammadalirana370]

nice lacturs sir ......

[@SunilKumar-eo3lp]

🙏🏻 thank u sir

[@kirankumarh351]

Thankyou sir❤🙏

[@techjunkiejdb5476]

Welcome

[@waelabulafi7566]

i think problem 3 has a mistake... you didnt count when t=0 the take the derivative of 1 as x(t)

[@techjunkiejdb5476]

wael abulafi it’s an integral . Not a derivative .

[@akshathanayak7954]

best explanation :)

[@techjunkiejdb5476]

Thanks

[@sushanthreddy9672]

Where is applications of Fourier represantations

[@chaithranayak1634]

nicely explained 👍

[@techjunkiejdb5476]

Thanks

[@noahnelson8387]

if you could turn off the autofocus on your camera so that it stops zooming out and in every time your hand comes in the shot that would be great

[@techjunkiejdb5476]

Noah Nelson yes . I have taken care of it in my future videos . 😊 Thank you .

[@bestskateboardsclub6147]

how to plot magnitude and phase of question 2

[@techjunkiejdb5476]

Fix the value of a to be some constant . Then apply omega value in the equation . U will get the magnitude plot . Phase plot would be zero !

[@bestskateboardsclub6147]

@@techjunkiejdb5476 thank you I fixed the value of a to be a and omega starting from zero to a

[@techjunkiejdb5476]

@@bestskateboardsclub6147 welcome !

[@bestskateboardsclub6147]

can you help me draw the phase and magnitude of the last question please?

[@techjunkiejdb5476]

Sinc function u r talking about . U get the CTFT and then follow the same procedure as I had told previously . Magnitude would be 2/omega . Plot this by giving different values to omega . Phase is -90

[@techjunkiejdb5476]

Integrating is finding the area under the curve . So if it’s discontinuous at t=o , then integration would be from minus infinite to zero and then zero to infinity . ! Only in case of discrete signals the summation is shifted form minus infinity to -1 and then 0 to infinity if there is a case of discontinutity 👍

[@bestskateboardsclub6147]

@@techjunkiejdb5476 for sinc functions do we have to apply L'hospital rule?

[@techjunkiejdb5476]

@@bestskateboardsclub6147 what r u finding ? Why differentiation ?

[@bestskateboardsclub6147]

@@techjunkiejdb5476 phase and magnitude spectrum of the sinc function

[@veggie_dose]

Thank you so much sir

[@techjunkiejdb5476]

Welcome

[@SUDHANSHUKUMAR-cw8lv]

I think your camera man is " LOL " , some time some good things are by default converted in to the worst things , only due to small mistake ( the mistake your camera man is doing ) , all time he is zooming in and zooming out the camera focus, i am unable to understand why he is doing so.... it's too irritating yr . BUT your teaching style is so pretty....

[@techjunkiejdb5476]

I had recorded using a tripod . 😷

[@patronarti5745]

Its trying to autofocus whenever there is a difference in the lighting 😅 not zoom in and out

[@akashjagtap2784]

Differenciation of u(t)=delta(t) hence X(jw)=1/jw

[@techjunkiejdb5476]

Exactly .

[@akashjagtap2784]

@@techjunkiejdb5476 but sir our teacher also give same answer that you have given So which is right 1/jw. Or the answer you have given

[@techjunkiejdb5476]

It's is addition of both .

[@akashjagtap2784]

@@techjunkiejdb5476 means final answer is pi*delta(jw)+1/jw

[@techjunkiejdb5476]

@@akashjagtap2784 yes . That's right . I have done wrong here

[@NikhilSwamiExperimental]

fix camera man....

[@techjunkiejdb5476]

Nikhil Swami ok shaktimaan 🤟🏻

[@webpage3870]

shortcut sucks

[@techjunkiejdb5476]

Thanks 👍