Fourier Transform with both Time Delay and Frequency Shift

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP












4












$begingroup$


I know that the Fourier transform of a function with time delay can be written as: $$mathscrFbigx(t-t_0)big=X(f)e^-j2pi f t_0$$



The Fourier transform of a function with frequency shift can also be written as: $$mathscrFBigx(t)e^j2pi f_0 tBig=X(f-f_0)$$



So what if we have both shift and delay at the time domain, what will be the result in the frequency domain? E.g.:



$$mathscrFBigx(t-t_0)e^j2pi f_0 (t-t_0)Big$$



Will the result be: $$X(f-f_0)e^-j 2 pi f (t-t_0)$$



Also what will be the result of:



$$mathscrFBigx(t-t_0)e^j2pi f_0 t)Big$$



Is there an order to apply these properties?










share|improve this question











$endgroup$







  • 1




    $begingroup$
    it's really nice to see new contributors use $LaTeX$. thanks.
    $endgroup$
    – robert bristow-johnson
    Feb 5 at 20:37















4












$begingroup$


I know that the Fourier transform of a function with time delay can be written as: $$mathscrFbigx(t-t_0)big=X(f)e^-j2pi f t_0$$



The Fourier transform of a function with frequency shift can also be written as: $$mathscrFBigx(t)e^j2pi f_0 tBig=X(f-f_0)$$



So what if we have both shift and delay at the time domain, what will be the result in the frequency domain? E.g.:



$$mathscrFBigx(t-t_0)e^j2pi f_0 (t-t_0)Big$$



Will the result be: $$X(f-f_0)e^-j 2 pi f (t-t_0)$$



Also what will be the result of:



$$mathscrFBigx(t-t_0)e^j2pi f_0 t)Big$$



Is there an order to apply these properties?










share|improve this question











$endgroup$







  • 1




    $begingroup$
    it's really nice to see new contributors use $LaTeX$. thanks.
    $endgroup$
    – robert bristow-johnson
    Feb 5 at 20:37













4












4








4


2



$begingroup$


I know that the Fourier transform of a function with time delay can be written as: $$mathscrFbigx(t-t_0)big=X(f)e^-j2pi f t_0$$



The Fourier transform of a function with frequency shift can also be written as: $$mathscrFBigx(t)e^j2pi f_0 tBig=X(f-f_0)$$



So what if we have both shift and delay at the time domain, what will be the result in the frequency domain? E.g.:



$$mathscrFBigx(t-t_0)e^j2pi f_0 (t-t_0)Big$$



Will the result be: $$X(f-f_0)e^-j 2 pi f (t-t_0)$$



Also what will be the result of:



$$mathscrFBigx(t-t_0)e^j2pi f_0 t)Big$$



Is there an order to apply these properties?










share|improve this question











$endgroup$




I know that the Fourier transform of a function with time delay can be written as: $$mathscrFbigx(t-t_0)big=X(f)e^-j2pi f t_0$$



The Fourier transform of a function with frequency shift can also be written as: $$mathscrFBigx(t)e^j2pi f_0 tBig=X(f-f_0)$$



So what if we have both shift and delay at the time domain, what will be the result in the frequency domain? E.g.:



$$mathscrFBigx(t-t_0)e^j2pi f_0 (t-t_0)Big$$



Will the result be: $$X(f-f_0)e^-j 2 pi f (t-t_0)$$



Also what will be the result of:



$$mathscrFBigx(t-t_0)e^j2pi f_0 t)Big$$



Is there an order to apply these properties?







fourier-transform time-frequency






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Feb 5 at 20:36









robert bristow-johnson

10.9k31548




10.9k31548










asked Feb 5 at 13:08









tamunotamuno

235




235







  • 1




    $begingroup$
    it's really nice to see new contributors use $LaTeX$. thanks.
    $endgroup$
    – robert bristow-johnson
    Feb 5 at 20:37












  • 1




    $begingroup$
    it's really nice to see new contributors use $LaTeX$. thanks.
    $endgroup$
    – robert bristow-johnson
    Feb 5 at 20:37







1




1




$begingroup$
it's really nice to see new contributors use $LaTeX$. thanks.
$endgroup$
– robert bristow-johnson
Feb 5 at 20:37




$begingroup$
it's really nice to see new contributors use $LaTeX$. thanks.
$endgroup$
– robert bristow-johnson
Feb 5 at 20:37










2 Answers
2






active

oldest

votes


















1












$begingroup$

As an alternative to going back to the definitions, as explained in Andy Walls' answer, you can also just apply the rules as you stated them:



$$mathcalFleftx(t-t_0)e^j2pi f_0(t-t_0)right=mathcalFleftx(t)e^j2pi f_0trighte^-j2pi ft_0=X(f-f_0)e^-j2pi ft_0$$



where $X(f)$ is the Fourier transform of $x(t)$.



And, for your second example, with $tildeX(f)=mathcalFx(t-t_0)=X(f)e^-j2pi ft_0$ you get



$$mathcalFleftx(t-t_0)e^j2pi f_0tright=tildeX(f-f_0)=X(f-f_0)e^-j2pi (f-f_0)t_0$$



Of course, recognizing that the function in the second example just equals the first function scaled by $e^j2pi f_0t_0$, we could have written down its Fourier transform directly by scaling the Fourier transform of the first function by the same factor.






share|improve this answer









$endgroup$




















    5












    $begingroup$

    If you are ever unsure, just go back to the definition and work out the Fourier Transform property for the specific situation:



    $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0left(t-t_0right)right &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0left(t-t_0right) e^-j2pi f tdt\
    \
    &= int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f left(tau+t_0right)dtau \
    \
    &= e^-j2pi ft_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
    \
    &= e^-j2pi ft_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
    \
    &= e^-j2pi ft_0 X(f-f_0)\
    \
    endalign*$$



    $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0 tright &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0t e^-j2pi f tdt\
    \
    &= int_-infty^infty xleft(tauright)e^j2pi f_0(tau+t_0) e^-j2pi f left(tau+t_0right)dtau \
    \
    &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
    \
    &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
    \
    &= e^-j2pi (f-f_0)t_0 X(f-f_0)\
    \
    endalign*$$






    share|improve this answer









    $endgroup$












      Your Answer





      StackExchange.ifUsing("editor", function ()
      return StackExchange.using("mathjaxEditing", function ()
      StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix)
      StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
      );
      );
      , "mathjax-editing");

      StackExchange.ready(function()
      var channelOptions =
      tags: "".split(" "),
      id: "295"
      ;
      initTagRenderer("".split(" "), "".split(" "), channelOptions);

      StackExchange.using("externalEditor", function()
      // Have to fire editor after snippets, if snippets enabled
      if (StackExchange.settings.snippets.snippetsEnabled)
      StackExchange.using("snippets", function()
      createEditor();
      );

      else
      createEditor();

      );

      function createEditor()
      StackExchange.prepareEditor(
      heartbeatType: 'answer',
      autoActivateHeartbeat: false,
      convertImagesToLinks: false,
      noModals: true,
      showLowRepImageUploadWarning: true,
      reputationToPostImages: null,
      bindNavPrevention: true,
      postfix: "",
      imageUploader:
      brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
      contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
      allowUrls: true
      ,
      noCode: true, onDemand: true,
      discardSelector: ".discard-answer"
      ,immediatelyShowMarkdownHelp:true
      );



      );













      draft saved

      draft discarded


















      StackExchange.ready(
      function ()
      StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdsp.stackexchange.com%2fquestions%2f55307%2ffourier-transform-with-both-time-delay-and-frequency-shift%23new-answer', 'question_page');

      );

      Post as a guest















      Required, but never shown

























      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      1












      $begingroup$

      As an alternative to going back to the definitions, as explained in Andy Walls' answer, you can also just apply the rules as you stated them:



      $$mathcalFleftx(t-t_0)e^j2pi f_0(t-t_0)right=mathcalFleftx(t)e^j2pi f_0trighte^-j2pi ft_0=X(f-f_0)e^-j2pi ft_0$$



      where $X(f)$ is the Fourier transform of $x(t)$.



      And, for your second example, with $tildeX(f)=mathcalFx(t-t_0)=X(f)e^-j2pi ft_0$ you get



      $$mathcalFleftx(t-t_0)e^j2pi f_0tright=tildeX(f-f_0)=X(f-f_0)e^-j2pi (f-f_0)t_0$$



      Of course, recognizing that the function in the second example just equals the first function scaled by $e^j2pi f_0t_0$, we could have written down its Fourier transform directly by scaling the Fourier transform of the first function by the same factor.






      share|improve this answer









      $endgroup$

















        1












        $begingroup$

        As an alternative to going back to the definitions, as explained in Andy Walls' answer, you can also just apply the rules as you stated them:



        $$mathcalFleftx(t-t_0)e^j2pi f_0(t-t_0)right=mathcalFleftx(t)e^j2pi f_0trighte^-j2pi ft_0=X(f-f_0)e^-j2pi ft_0$$



        where $X(f)$ is the Fourier transform of $x(t)$.



        And, for your second example, with $tildeX(f)=mathcalFx(t-t_0)=X(f)e^-j2pi ft_0$ you get



        $$mathcalFleftx(t-t_0)e^j2pi f_0tright=tildeX(f-f_0)=X(f-f_0)e^-j2pi (f-f_0)t_0$$



        Of course, recognizing that the function in the second example just equals the first function scaled by $e^j2pi f_0t_0$, we could have written down its Fourier transform directly by scaling the Fourier transform of the first function by the same factor.






        share|improve this answer









        $endgroup$















          1












          1








          1





          $begingroup$

          As an alternative to going back to the definitions, as explained in Andy Walls' answer, you can also just apply the rules as you stated them:



          $$mathcalFleftx(t-t_0)e^j2pi f_0(t-t_0)right=mathcalFleftx(t)e^j2pi f_0trighte^-j2pi ft_0=X(f-f_0)e^-j2pi ft_0$$



          where $X(f)$ is the Fourier transform of $x(t)$.



          And, for your second example, with $tildeX(f)=mathcalFx(t-t_0)=X(f)e^-j2pi ft_0$ you get



          $$mathcalFleftx(t-t_0)e^j2pi f_0tright=tildeX(f-f_0)=X(f-f_0)e^-j2pi (f-f_0)t_0$$



          Of course, recognizing that the function in the second example just equals the first function scaled by $e^j2pi f_0t_0$, we could have written down its Fourier transform directly by scaling the Fourier transform of the first function by the same factor.






          share|improve this answer









          $endgroup$



          As an alternative to going back to the definitions, as explained in Andy Walls' answer, you can also just apply the rules as you stated them:



          $$mathcalFleftx(t-t_0)e^j2pi f_0(t-t_0)right=mathcalFleftx(t)e^j2pi f_0trighte^-j2pi ft_0=X(f-f_0)e^-j2pi ft_0$$



          where $X(f)$ is the Fourier transform of $x(t)$.



          And, for your second example, with $tildeX(f)=mathcalFx(t-t_0)=X(f)e^-j2pi ft_0$ you get



          $$mathcalFleftx(t-t_0)e^j2pi f_0tright=tildeX(f-f_0)=X(f-f_0)e^-j2pi (f-f_0)t_0$$



          Of course, recognizing that the function in the second example just equals the first function scaled by $e^j2pi f_0t_0$, we could have written down its Fourier transform directly by scaling the Fourier transform of the first function by the same factor.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Feb 5 at 17:15









          Matt L.Matt L.

          50.6k23889




          50.6k23889





















              5












              $begingroup$

              If you are ever unsure, just go back to the definition and work out the Fourier Transform property for the specific situation:



              $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0left(t-t_0right)right &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0left(t-t_0right) e^-j2pi f tdt\
              \
              &= int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f left(tau+t_0right)dtau \
              \
              &= e^-j2pi ft_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
              \
              &= e^-j2pi ft_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
              \
              &= e^-j2pi ft_0 X(f-f_0)\
              \
              endalign*$$



              $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0 tright &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0t e^-j2pi f tdt\
              \
              &= int_-infty^infty xleft(tauright)e^j2pi f_0(tau+t_0) e^-j2pi f left(tau+t_0right)dtau \
              \
              &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
              \
              &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
              \
              &= e^-j2pi (f-f_0)t_0 X(f-f_0)\
              \
              endalign*$$






              share|improve this answer









              $endgroup$

















                5












                $begingroup$

                If you are ever unsure, just go back to the definition and work out the Fourier Transform property for the specific situation:



                $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0left(t-t_0right)right &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0left(t-t_0right) e^-j2pi f tdt\
                \
                &= int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f left(tau+t_0right)dtau \
                \
                &= e^-j2pi ft_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
                \
                &= e^-j2pi ft_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
                \
                &= e^-j2pi ft_0 X(f-f_0)\
                \
                endalign*$$



                $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0 tright &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0t e^-j2pi f tdt\
                \
                &= int_-infty^infty xleft(tauright)e^j2pi f_0(tau+t_0) e^-j2pi f left(tau+t_0right)dtau \
                \
                &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
                \
                &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
                \
                &= e^-j2pi (f-f_0)t_0 X(f-f_0)\
                \
                endalign*$$






                share|improve this answer









                $endgroup$















                  5












                  5








                  5





                  $begingroup$

                  If you are ever unsure, just go back to the definition and work out the Fourier Transform property for the specific situation:



                  $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0left(t-t_0right)right &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0left(t-t_0right) e^-j2pi f tdt\
                  \
                  &= int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f left(tau+t_0right)dtau \
                  \
                  &= e^-j2pi ft_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
                  \
                  &= e^-j2pi ft_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
                  \
                  &= e^-j2pi ft_0 X(f-f_0)\
                  \
                  endalign*$$



                  $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0 tright &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0t e^-j2pi f tdt\
                  \
                  &= int_-infty^infty xleft(tauright)e^j2pi f_0(tau+t_0) e^-j2pi f left(tau+t_0right)dtau \
                  \
                  &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
                  \
                  &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
                  \
                  &= e^-j2pi (f-f_0)t_0 X(f-f_0)\
                  \
                  endalign*$$






                  share|improve this answer









                  $endgroup$



                  If you are ever unsure, just go back to the definition and work out the Fourier Transform property for the specific situation:



                  $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0left(t-t_0right)right &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0left(t-t_0right) e^-j2pi f tdt\
                  \
                  &= int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f left(tau+t_0right)dtau \
                  \
                  &= e^-j2pi ft_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
                  \
                  &= e^-j2pi ft_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
                  \
                  &= e^-j2pi ft_0 X(f-f_0)\
                  \
                  endalign*$$



                  $$beginalign*mathscrFleftxleft(t-t_0right)e^j2pi f_0 tright &= int_-infty^infty xleft(t-t_0right)e^j2pi f_0t e^-j2pi f tdt\
                  \
                  &= int_-infty^infty xleft(tauright)e^j2pi f_0(tau+t_0) e^-j2pi f left(tau+t_0right)dtau \
                  \
                  &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright)e^j2pi f_0tau e^-j2pi f taudtau \
                  \
                  &= e^-j2pi (f-f_0)t_0int_-infty^infty xleft(tauright) e^-j2pi (f-f_0) taudtau \
                  \
                  &= e^-j2pi (f-f_0)t_0 X(f-f_0)\
                  \
                  endalign*$$







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Feb 5 at 14:20









                  Andy WallsAndy Walls

                  1,459127




                  1,459127



























                      draft saved

                      draft discarded
















































                      Thanks for contributing an answer to Signal Processing Stack Exchange!


                      • Please be sure to answer the question. Provide details and share your research!

                      But avoid


                      • Asking for help, clarification, or responding to other answers.

                      • Making statements based on opinion; back them up with references or personal experience.

                      Use MathJax to format equations. MathJax reference.


                      To learn more, see our tips on writing great answers.




                      draft saved


                      draft discarded














                      StackExchange.ready(
                      function ()
                      StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdsp.stackexchange.com%2fquestions%2f55307%2ffourier-transform-with-both-time-delay-and-frequency-shift%23new-answer', 'question_page');

                      );

                      Post as a guest















                      Required, but never shown





















































                      Required, but never shown














                      Required, but never shown












                      Required, but never shown







                      Required, but never shown

































                      Required, but never shown














                      Required, but never shown












                      Required, but never shown







                      Required, but never shown






                      Popular posts from this blog

                      How to check contact read email or not when send email to Individual?

                      Bahrain

                      Postfix configuration issue with fips on centos 7; mailgun relay