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Information About

Transfer Function




A transfer function is a mathematical representation of the relation between the input and output of a ( Linear Time-invariant ) System .


EXPLANATION

The transfer function is commonly used in the analysis of single-input single-output Analog Electronic Circuits , for instance. It is mainly used in Signal Processing , Communication Theory , and Control Theory . The term is often used exclusively to refer to Linear, Time-invariant Systems (LTI), as covered in this article. Most real systems have Non-linear input/output characteristics, but many systems, when operated within nominal parameters (not "over-driven") have behavior that is close enough to linear that LTI System Theory is an acceptable representation of the input/output behavior.

In its simplest form for Continuous-time input signal x(t)\, and output y(t)\,, the transfer function is the linear mapping of the Laplace Transform of the input, X(s)\,, to the output Y(s)\,:

: Y(s) = H(s) \, X(s)
or
: H(s) = rac{Y(s)} {X(s)} = rac { \mathcal{L}\left\{y(t) ight\} } { \mathcal{L}\left\{x(t) ight\} }

where H(s)\, is the transfer function of the LTI system.

In Discrete-time systems, the function is similarly written as H(z) = rac{Y(z)}{X(z)} (see Z Transform ).


SIGNAL PROCESSING


Let x(t) \ be the input to a general Linear Time-invariant System , and y(t) \ be the output, and the Laplace Transform of x(t) \ and y(t) \ be

: X(s) = \mathcal{L}\left \{ x(t) ight \} \ \stackrel{\mathrm{def}}{=}\ \int_{-\infty}^{\infty} x(t) e^{-st}\, dt

: Y(s) = \mathcal{L}\left \{ y(t) ight \} \ \stackrel{\mathrm{def}}{=}\ \int_{-\infty}^{\infty} y(t) e^{-st}\, dt .

Then the output is related to the input by the transfer function H(s) \ as

:: Y(s) = H(s) X(s) \,

and the transfer function itself is therefore

:: H(s) = rac{Y(s)} {X(s)} .

  :<math> X(t) Xe^{j\omega t} = Xe^{j(\omega t + \arg(X))} </math>
  :where <math> X Xe^{j\arg(X)} </math>
  :<math> Y(t) Ye^{j\omega t} = Ye^{j(\omega t + \arg(Y))} </math>
  :and <math> Y Ye^{j\arg(Y)} </math>