PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

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Time Domain Representation of Continuous

and Discrete Signals

This time, like all time, is a very good one, if we know what to do with it. Time is the

most valuable and the most perishable of all possessions.

Ralph Waldo Emerson

1.1 Introduction

Signals are physical variables that carry information about a particular process or event
of interest. Signals are defi ned mathematically over a range and domain of interest, and
constitute different things to different people.

To an electrical engineer, it may be

• A current


• A voltage


• Power


• Energy
  To a mechanical engineer, it may be


• A force


• A torque


• A velocity


• A displacement
  To an economist, it may be


• Growth (GNP)


• Employment rate


• Prime interest rate


• Infl ation rate


• The stock market variations
  To a meteorologist, it may be


• Atmospheric temperature


• Atmospheric humidity


• Atmospheric pressures or depressions


• Wind speed
  To a geophysicist, it may be


• Seismic waves


• Tsu na m is


• Volcanic activity