Finding a Fourier representation of a signal

In summary, the signal is periodic with a period of T. It has a 0 value for time values larger than T, so graphing it would be tricky.
  • #1
Adir_Sh
22
0
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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  • #2
Hint: Is the function periodic in the time domain? What implications does that have for the answer?
 
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  • #3
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.
 
  • #4
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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FAQ: Finding a Fourier representation of a signal

1. What is a Fourier representation of a signal?

A Fourier representation of a signal is a mathematical expression that breaks down a signal into its component frequencies. It shows the amplitude and phase of each frequency component, allowing us to analyze the signal's frequency content.

2. How is a Fourier representation calculated?

A Fourier representation is calculated using a mathematical technique called the Fourier Transform. This involves breaking down a signal into its individual sinusoidal components using complex numbers and integrating over all frequencies.

3. Why is finding a Fourier representation important?

Finding a Fourier representation is important because it allows us to understand the frequency characteristics of a signal. This is useful in many applications, such as signal processing, image and sound analysis, and communications.

4. What is the difference between a Fourier representation and a Fourier series?

A Fourier representation is a continuous representation of a signal, while a Fourier series is a discrete representation. A Fourier series is used for periodic signals, while a Fourier representation can be used for both periodic and non-periodic signals.

5. Can any signal be represented by a Fourier series?

No, not every signal can be represented by a Fourier series. The signal must be periodic, and its Fourier coefficients must exist for the series to converge. If these conditions are not met, a Fourier representation may be used instead.

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