Fourier Transform in the Form of Dirac-Delta Function

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SUMMARY

The Fourier transform of the function x(t)=8cos(70πt)+4sin(132πt)+8cos(24πt) is expressed in terms of Dirac delta functions. The derived formula is X(f)=4π(δ(ω+70π)+δ(ω−70π)) + (2π/j)(δ(ω+132π)−δ(ω−132π)) + 4π(δ(ω+24π)+δ(ω−24π)). This result utilizes the properties of the Fourier transform for cosine and sine functions, specifically the integrals involving delta functions.

PREREQUISITES
  • Understanding of Fourier Transform concepts
  • Familiarity with Dirac Delta Function properties
  • Knowledge of trigonometric identities in complex form
  • Experience with integral calculus
NEXT STEPS
  • Study the properties of the Fourier Transform in detail
  • Learn about the applications of Dirac Delta Functions in signal processing
  • Explore the derivation of Fourier Transform pairs for various functions
  • Investigate the implications of Fourier analysis in real-world signals
USEFUL FOR

This discussion is beneficial for students and professionals in electrical engineering, signal processing, and applied mathematics, particularly those focusing on Fourier analysis and its applications in analyzing periodic signals.

Captain1024
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Homework Statement


Given x(t)=8cos(70\pi t)+4sin(132\pi t)+8cos(24\pi t), find the Fourier transform X(f) in the form of \delta function.

Homework Equations


X(f)=\int ^{\infty}_{-\infty}x(t)e^{-j\omega _0t}dt
cos(\omega t)=\frac{e^{j\omega t}+e^{-j\omega t}}{2}
sin(\omega t)=\frac{e^{j\omega t}-e^{-j\omega t}}{2j}
\int ^{\infty}_{-\infty}cos(\omega _0t)e^{-j\omega t}dt=\frac{\pi}{2}(\delta (\omega +\omega _0)+\delta (\omega -\omega _0))
\int ^{\infty}_{-\infty}sin(\omega _0t)e^{-j\omega t}dt=\frac{\pi}{j2}(\delta (\omega +\omega _0)-\delta (\omega -\omega _0))

The Attempt at a Solution


X(f)=\frac{8\pi}{2}(\delta (\omega +70\pi)+\delta (\omega -70\pi))+\frac{4\pi}{j2}(\delta (\omega +132\pi)-\delta (\omega -132\pi))+\frac{8\pi}{2}(\delta (\omega +24\pi)+\delta (\omega -24\pi))

Simplifying: X(f)=4\pi (\delta (\omega +70\pi)+\delta (\omega -70\pi))+\frac{2\pi}{j} (\delta (\omega +132\pi)-\delta (\omega -132\pi))+4\pi (\delta (\omega +24\pi)+\delta (\omega -24\pi))
 
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All clear, Captain!
(You could changew +1/2j to -j/2 but that would be quibbling!)
Nice work.
 

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