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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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24 TheFouriertransform

Contents 24.1 Introduction 757

24.2 TheFouriertransform--definitions 758

24.3 SomepropertiesoftheFouriertransform 761

24.4 Spectra 766

24.5 Thet−ω dualityprinciple 768

24.6 Fouriertransformsofsomespecialfunctions 770

24.7 TherelationshipbetweentheFouriertransformandthe

Laplacetransform 772

24.8 Convolutionandcorrelation 774

24.9 ThediscreteFouriertransform 783

24.10 Derivationofthed.f.t. 787

24.11 Usingthed.f.t.toestimateaFouriertransform 790

24.12 Matrixrepresentationofthed.f.t. 792

24.13 Somepropertiesofthed.f.t. 793

24.14 Thediscretecosinetransform 795

24.15 Discreteconvolutionandcorrelation 801

Reviewexercises24 821

24.1 INTRODUCTION

Wehaveseenthatalmostanyperiodicsignalcanberepresentedasalinearcombination

ofsineandcosinewavesofvariousfrequenciesandamplitudes.Allfrequenciesareintegermultiplesofthefundamental.However,manypracticalwaveformsarenotperiodic.

Examples are pulse signals and noise signals. The function shown in Figure 24.1 is an

example of a non-periodic signal.

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