Finding a Fourier representation of a signal

AI Thread Summary
The discussion focuses on finding the Fourier representation of a piecewise signal defined over specific intervals. Participants debate whether to use a Fourier series or Fourier transform, ultimately leaning towards the Fourier transform due to the signal's characteristics. The signal is noted to be periodic with a period T, but confusion arises regarding its behavior outside this period. There is acknowledgment that the Fourier transform will yield both real and imaginary components, complicating the sketching of V(jf). The conversation highlights the importance of correctly interpreting the signal's periodicity and the implications for its Fourier representation.
Adir_Sh
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Given the following signal, find the Fourier representation, ##V(jf)= \mathfrak{F}\left \{ v(t) \right \}##:

##
v(t)=\left\{\begin{matrix}
A, & 0\leqslant t\leqslant \frac{T}{3}\\
2A, & \frac{T}{3}\leqslant t\leqslant T\\
0, & Else
\end{matrix}\right.
##

Then sketch ##V(jf)##.

Homework Equations

:[/B]
I don't know whether in such a given form of a signal (apparently looks quite simple, involving constants only) I should use a Fourier SERIES representation or a Fourier TRANSFORM representation. If it's a Fourier Transform representation, then I don't know how would the signal look like in the frequency domain. I tried to Calculate the Transform according to its definition, yet couldn't quite get to anything "sketchable", at least not something I can see it.

The Attempt at a Solution

:[/B]
Given below:
https://lh3.googleusercontent.com/RyZyGteipLYWd0P_Wp-lIOTGLqc2ZhrSdu22MgjI_S65ul7lYjivK5Tt5dOd-P-DdAdEztuVWdfy-2BK3FOEufhfdNqACycPa3pLYl1NGUjqFphMDJfK0MxlqSJKlM3Nhx1FlHIYCypqTekUrmj0y4sGwWpHWwuuIQMKlcck8aY8jJkEzv71Rg9AxcYheJ-Nr2lVLTnZ1jXf2FPQhbsTBR5aX1xDc3RyFYbmPHddMUAn0YA0xVL7hkejWtD6SEK_0ZP_qd2mUiW0STSbKE5bfHaypjezUVle-t8WBNz-WpVmCs8n12_bkKHpN2VPI3PQSAHE3VF9oJwa4iuTBiX0SQZc1FFcjzMrqy86xtEt_8r8v1qVKz2a8UpF_2g_86Tszy-ANPbwb25SuS41kk85QGpKJjjm0CKKoEyLaBFVisFIWQwIhNb9bDsEBfvl_nTTz8OISX88diDUyhbrN7rV7gcVxHvugexaZ2IVHkpbmXm2hYRI1lxOX21OEuxP4VoTbZAWcFXhl5b3Q4yo565BuF1ea3yQSH77PT0-mhQdWj2V=w1144-h643-no


Thanks in advance for your help,

Adir.
 
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Hint: Is the function periodic in the time domain? What implications does that have for the answer?
 
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Dr. Courtney said:
Hint: Is the function periodic in the time domain? What implications does that have for the answer?
It is periodic in the sense that it has a period ##T##. However, It has a 0 value for time values larger than T, so that's a bit tricky to determine the signal's periodicity. But that's the first "mine" in finding my way here.
 
Adir_Sh said:
It is periodic in the sense that it has a period ##T##. However, It has a 0 value for time values larger than T, so that's a bit tricky to determine the signal's periodicity. But that's the first "mine" in finding my way here.
Either it's periodic or it's zero for t > T. Can't have it both ways.
It sure looks like you're supposed to find the Fourier transform (integral).
Don't know about "graphing" V(jf). It may have real and imaginary parts; I don't have the time to look at your math in detail but if you did it right there are indeed real and imaginary parts to the transform. Which means I don't know about graphing the function. But maybe you messed up somewhere & there are only real or imaginary parts so then you could graph that.
Ther is an expression for the energy spectral density between two frequencies f1 and f2, given the Fourier integral of a pulse, but it's kind of advanced. But that can be graphed since it's a real number.
 
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