Understanding the Differences between Fourier Series and Fourier Transforms

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Discussion Overview

The discussion revolves around the differences between Fourier Series and Fourier Transforms, focusing on their mathematical representations, applications, and implications in signal processing. Participants explore the nature of amplitude and phase representation in both methods.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Salil questions whether Fourier Transforms provide actual amplitude and phase information similar to Fourier Series.
  • One participant suggests that while Fourier Transforms can provide amplitude, the inverse continuous Fourier transform is an integral rather than a summation, indicating a relationship between the two methods.
  • Another participant notes that the Fourier Series is a discrete process, whereas the Fourier Transform is continuous, and warns that ignoring basic rules can lead to misleading results.
  • There is a query about the Fourier transform of a specific sum involving cosine functions, with an assumption made about the notation used for coefficients.
  • A participant proposes that the transform will yield a 'comb' of frequency components, with amplitudes determined by the coefficients, suggesting that the original function's frequency spectrum can be observed directly.
  • One participant clarifies their use of "sum" in contrast to "integral," seeking confirmation on their understanding.

Areas of Agreement / Disagreement

Participants express differing views on the nature of Fourier Series and Transforms, particularly regarding their mathematical properties and implications. No consensus is reached on the nuances of their relationship or the specifics of the Fourier transform of the given sum.

Contextual Notes

Participants mention the importance of understanding the basic rules governing Fourier Series and Transforms, indicating potential limitations in their applications if these rules are overlooked. There is also a reliance on specific mathematical definitions that may not be universally agreed upon.

salil87
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Hi
Do Fourier Transforms give us actual amplitude/phase of the particular frequency (ejωt) just like Fourier series?
Thanks
Salil
 
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sorta, yes. but the inverse continuous Fourier transform is an integral not a summation like in the Fourier series. so the actual amplitude is proportional to the product of X(f) and the width of the sliver of spectrum df.

to compare, give the (inverse) Fourier integral a finite width (with the limits of the integral) and then represent that finite width integral with a Riemann summation and then you will be able to see the relationship between the inverse Fourier transform and the Fourier series. in a loose sense, they are the same thing.
 
The series is a Discrete process where the Transform is Continuous. The series can yield 'wrong' / misleading results if you ignore the basic rules.
 
what is the Fourier transform of sum( Vhcos(hwt)) where h varies from 1 to infinity
 
Anitha Sankar said:
what is the Fourier transform of sum( Vhcos(hwt)) where h varies from 1 to infinity

Hi
I assume that when you write Vh , the h is a suffix.
The transform will be a regular 'comb' of components at frequency w, hw, 2hw etc. with amplitdes given by the coefficients V. In fact, the original function is of a form that tells you the frequency spectrum just by 'observation'.
 
http://www.infoocean.info/avatar2.jpg The series is a Discrete process where the Transform is Continuous.
 
Last edited by a moderator:
I guess I meant "sum' as against 'integral'.
Is that better?
 
Last edited:

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