DFT Symmetry Property: Why Does the Answer Not Void This Property?

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SUMMARY

The discussion centers on the Discrete Fourier Transform (DFT) symmetry property, specifically addressing the DFT of the sequence x[n]={1,1,0,1}, resulting in X(m)={3,1,-1,1}. The symmetry property states that for real data, X_k equals the complex conjugate of X_{N-k}. In this case, with N=4, the values X_0=3, X_1=1, X_2=-1, and X_3=1 satisfy the symmetry condition, confirming that the DFT does not violate this property.

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  • Understanding of Discrete Fourier Transform (DFT)
  • Familiarity with complex numbers and their conjugates
  • Knowledge of symmetry properties in signal processing
  • Basic grasp of summation notation and exponential functions
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This discussion is beneficial for students and professionals in electrical engineering, signal processing, and applied mathematics, particularly those studying Fourier analysis and its properties.

Shaheers
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Homework Statement



As an example, if we find a DFT of x[n]={1,1,0,1}
the result will be X(m)={3,1,-1,1}


Homework Equations



My Question is that as we know DFT holds symmetry property, why this answer does not void for that property?
 
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Let's take the definition from Wikipedia:
[tex]X_k=\sum_{n=0}^{N-1}x_n\,e^{-i2\pi kn/N}[/tex]
For real data you have then the symmetry:
[tex]X_k=\bar{X}_{N-k},\, (k=1,...,N).[/tex]
In your case [itex]N=4[/itex], and you have [itex]X_0=3,X_1,=1,X_2=-1,X_3=1,[/itex] all real.

From the symmetry property you should have [itex]X_4=X_0,X_3=X_1,X_2=X_2[/itex].
And you have it ([itex]X_4[/itex] can be thought of as defined by the symmetry property).
 
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