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Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

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Page 1: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Discrete-Time Fourier Methods

M. J. Roberts - All Rights Reserved. Edited

by Dr. Robert Akl

1

Page 2: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Discrete-Time Fourier Series Concept

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Page 3: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 4: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 5: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 6: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 7: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 8: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 9: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 10: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Discrete-Time Fourier Series Concept

Page 11: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Discrete-Time Fourier Series

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Page 12: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Discrete Fourier Transform

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Page 13: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Discrete Fourier Transform

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Page 14: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Discrete Fourier Transform

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Page 15: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DFT Example

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Page 16: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 17: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 18: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 19: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 20: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 21: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 22: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl

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Page 23: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 24: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 25: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The DFT Harmonic Function

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Page 26: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Convergence of the DFT

• The DFT converges exactly with a finite number of terms. It does not have a “Gibbs phenomenon” in the same sense that the CTFS does

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Page 27: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Discrete Fourier Transform

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Page 28: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DFT Properties

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Page 29: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DFT Properties

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Page 30: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DFT Properties

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Page 31: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Dirichlet Function

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Page 32: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DFT Pairs

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Page 33: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Fast Fourier Transform

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Page 34: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Fast Fourier Transform

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Page 35: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Generalizing the DFT for Aperiodic Signals

Pulse Train

This periodic rectangular-wave signal is analogous to thecontinuous-time periodic rectangular-wave signal used toillustrate the transition from the CTFS to the CTFT.

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Page 36: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DFT of Pulse Train

As the period of the rectangular wave increases, the period of the DFT increases

Generalizing the DFT for Aperiodic Signals

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Page 37: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

NormalizedDFT of

Pulse Train

Generalizing the DFT for Aperiodic Signals

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Page 38: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The normalized DFT approaches this limit as theperiod approaches infinity.

Generalizing the DFT for Aperiodic Signals

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Page 39: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Definition of the Discrete-Time Fourier

Transform (DTFT)

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Page 40: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Discrete-Time Fourier Transform

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Page 41: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Pairs

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Page 42: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Generalized DTFT

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Page 43: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Generalized DTFT

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Page 44: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Generalized DTFT

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Page 45: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Forward DTFT Example

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Page 46: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Forward DTFT Example

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Page 47: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Forward DTFT Example

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Page 48: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

More DTFT Pairs

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Page 49: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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DTFT Properties

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Page 51: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 52: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 53: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 54: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 55: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 56: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 57: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

DTFT Properties

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Page 58: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Transform Method Comparisons

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Page 59: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Transform Method Comparisons

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Page 60: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Transform Method Comparisons

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Page 61: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Transform Method Comparisons

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Page 62: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Transform Method Comparisons

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Transform Method Comparisons

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Transform Method Comparisons

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Transform Method Comparisons

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Transform Method Comparisons

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Transform Method Comparisons

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Page 68: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

The Four Fourier Methods

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Page 69: Discrete-Time Fourier Methods M. J. Roberts - All Rights Reserved. Edited by Dr. Robert Akl 1

Relations Among Fourier Methods

Multiplication-Convolution Duality

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Relations Among Fourier Methods

Parseval’s Theorem

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Relations Among Fourier Methods

Time and Frequency Shifting

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Relations Among Fourier Methods

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