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Unformatted text preview: Signals and Signal Properties Prof. Adnan Kavak Dept. of Electrical and Computer Engineering The University of Texas at Austin EE 313 Linear Systems and Signals Fall 2008 22 Signals Signal is a set of data or information, which is a function of an independent variable (time, space, etc) E.g. Phone or TV signal, monthly sales of corporation, daily stock price, daily temperature, etc. Continuoustime signals are functions of a real argument x ( t ) where t can take any real value x ( t ) may be 0 for a given range of values of t Discretetime signals are functions of an argument that takes values from a disrete set x [ n ] where n {...3,2,1,0,1,2,3...} We sometimes use index instead of time when discussing discretetime signals 23 Signal Energy For a realvalued signal For a complexvalued signal (To make sure that energy is real, use magnitude square) Measure of the signal size as the area under its amplitude square 24 Comment: Why do we use amplitude square for energy? Instantenous power: p(t) = i(t) * v(t) (in general) f(t) = i(t) = v(t) [ Assuming 1 Ohm resistance] Then, instantenous power: p(t) = f(t) * f(t) This is why we use square of the signal amplitude (physical reason). Then, energy is integral of the instantenous power. Mathematically, if we didnt use square of amplitude, then energy may be negative which doesnt make any sense. 25 Remarks about Signal Energy Signal energy is always positive Some signals (e.g. periodic) have infinite energy....
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This note was uploaded on 02/10/2009 for the course EE 313 taught by Professor Cardwell during the Spring '07 term at University of Texas at Austin.
 Spring '07
 Cardwell

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