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Brief Introduction

Signal processing is much important.

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Laplace Transform (LS)

Lapace transform is an integral transformation of a function from the time domain to the complex frequency (s=¦Ä+j¦Ø) domain.

Given f(t), its Laplace transform is defined by

- one-sided(or unilateral) Laplace transform, discussed here

    -two-sided(or bilateral) Laplace transform,not discussed here

where s=¦Ä+j¦Ø has the dimensions of frequency, whose unit is 1/sec. or Hz.

 

And its inverse Laplace transform is given by

where the intergraion is performed along a line ¦Ä1+j¦Ø(-¡Þ<¦Ø<¡Þ).

 

The condition for f(t) to have a Laplace transform is

, for ¦Ä>¦Äc.

 

Properties of Laplace Transform

Linearity

Scaling

Time Shift(Time Delay)

Frequency Shift(Frequency Translation)

Time Differentiation

Time Integration

Frequency Differentiation

Time Periodicity

where F1(s) is the Laplace transform of f(t) over the 1st period.

Initial and Final Values

Convolution

Laplace Transform Pairs

 

Inverse Laplace Transform

F(s) can be written in general form as

and the roots of N(s) are called zeros of F(s) , while the roots of D(s) are called poles of F(s).

The above F(s) can be broken down to simple terms by partial fraction expansion,and obtain the inverse tranform of each them,then combine them together to obtain the final result.

Simple Poles

For below simple poles,

The parameters of k1,k2,...,kn can be calculated by residue method.

The inverse Laplace transform is

 

Repeated Poles

For below repeated poles

The inverse Laplace transform is

Complex Poles

Complex poles pair is processed by the method of 'completing the square'to simplify the analysis.

For below complex poles

where,

The inverse Laplace transform is

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Basic
  Compelx Number
  Even and Odd Function
  Fourier Series(FS)
  Fourier Transform(FT)
  Discrete Fourier Transform(DFT)
  Discrete Fourier Series(DFS)
  Laplace Transform(LT)
Technical Note
 Sinc Wave and its Spectrum