Fourier Transforms Flashcards

1
Q

What does a Fourier series do?

A

Represents a periodic function as a sum of sines and cosines to find frequency/wavelength components

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2
Q

What does a0 represent?

A

The average of the function

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3
Q

What does a square wave consist of?

A

Sine terms and the odd harmonics

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4
Q

Definition of odd function

A

Reflection in y-axis with an inversion f(x)=f(-x)

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5
Q

Definition of even function

A

Reflection in y-axis f(x)=-f(-x)

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6
Q

FS of an even function

A

Only contains cos terms (bn’s are zero)

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7
Q

FS of an odd function

A

Only contains sin terms (an’s are zero)

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8
Q

Way of simplifying with symmetry

A

Don’t need to split integration, just multiply by 2

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9
Q

What does a Fourier transform do?

A

Represents a non periodic function

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10
Q

What does the FT of a single pulse look like

A

A continuum

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11
Q

Type of function produced by a FT

A

a sinc(x) function - sinx/x

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12
Q

Relationship with top hat and its FT

A

The width of the FT is inversly proportional to the width of the top hat

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13
Q

FT of even and odd functions

A

Even - Real Transform Odd - Complex Transform

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14
Q

Definition of convolution

A

Mathematical function taking two functions and outputting a third

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15
Q

Physical Application of convolution

A

One function is being measured One function is the response of the measuring system The output is the combination and what we actually receive as the measurement

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16
Q

What is the convolution theorem?

A

The fourier transform of the convolution is the product of the Fouriers of the original functions

17
Q

What does convolution show?

A

How measurement distorts the system

18
Q

How to deal with convolution

A

Introduce dummy variable u

19
Q

Integrating function with a delta gives

A

Gives original function centred on delta