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    difference between laplace and fourier transform

    What are the differences?
    I mean when we will make a decision "hmm now i must use laplace transform or now i must use fourier transform".

    What are the absences in laplace transform so fourier design a new transfom?

    I want to know these transforms' main idea, differences.

    I am looking for your answers.

    Thanks .
    Sincerely;

    •   Alt23rd May 2006, 09:17

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    laplace vs fourier

    for all signals we can have laplace transform but we can have fourier transform only for ceratin cases...Fourier transform needs certain conditions caled as Dirchlet conditions whereas laplace wont need anything like this....


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    •   Alt23rd May 2006, 10:15

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    difference between laplace and fourier

    Quote Originally Posted by electronics_kumar
    for all signals we can have laplace transform but we can have fourier transform only for ceratin cases...Fourier transform needs certain conditions caled as Dirchlet conditions whereas laplace wont need anything like this....
    Can you explain this concept please?I need some details..

    Thanks...



    •   Alt23rd May 2006, 11:07

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    fourier vs laplace

    Quote Originally Posted by serimc
    Quote Originally Posted by electronics_kumar
    for all signals we can have laplace transform but we can have fourier transform only for ceratin cases...Fourier transform needs certain conditions caled as Dirchlet conditions whereas laplace wont need anything like this....
    Can you explain this concept please?I need some details..

    Thanks...
    http://lofi.forum.physorg.com/Laplac...urier_403.html

    http://www.dsprelated.com/showmessage/39243/1.php

    http://www.physicsforums.com/showthread.php?t=40770


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    laplace vs. fourier

    in a simple expression:

    Laplas Transform does a real transformation on complex data but Fourier Tranform does a complex transformation on real data.
    it means:

    L(σ1+jω1)=σ2+jω2
    F(ω1)=|ω2|<ω2

    at the presence of some condition you can take the Fourier transformation by placing instead of s in Laplas tranform.



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    laplace vs fourier transform

    theoretically..laplace represents σ + jw and is in all of the s-plane while in fourier its only in the jw axis of this s-plane..so basically we are setting the real part of the exponenntial to 0 and hence
    it will give you the features for steady state for a sinusoidal input
    and in the case of laplace it will tel u for rising or fallin sinusoidal.
    i hope that shud answer ur question..


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    laplas transform

    For a good explanation you can consult the book PLL, or Roland E. Best, that you can find in this forum.

    As my colegees said Laplace transform translate f(t) to σ + ωi domain, while Fourier translate f(t) to w domain.

    that means Laplace has information of time and frequency that's why we use to study transitory circuits. But Fourier dosn't have all the information i this case fase and wave forms only frecquency and amplitude.



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    fourier versus laplace

    Quote Originally Posted by shivamrules
    theoretically..laplace represents σ + jw and is in all of the s-plane while in fourier its only in the jw axis of this s-plane..so basically we are setting the real part of the exponenntial to 0 and hence
    it will give you the features for steady state for a sinusoidal input
    and in the case of laplace it will tel u for rising or fallin sinusoidal.
    i hope that shud answer ur question..


    for lapalce transform, it is (σ + jw) when you are going to Fourier transform it become (0 + jw )..i mean σ =0 no attenuation in the system...



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