20-11-2012, 06:25 PM
Signals and Systems
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SIGNALS
Signals are functions of independent variables that carry information. For example:
•Electrical signals ---voltages and currents in a circuit
•Acoustic signals ---audio or speech signals (analog or digital)
•Video signals ---intensity variations in an image (e.g. a CAT scan)
•Biological signals ---sequence of bases in a gene
THE INDEPENDENT VARIABLES
•Can be continuous—Trajectory of a space shuttle—Mass density in a cross-section of a brain
•Can be discrete—DNA base sequence—Digital image pixels
•Can be 1-D, 2-D,
••• N-D
•For this course: Focus on a single (1-D) independent variable which we call“time”. Continuous-Time (CT) signals: x(t), t—continuous valuesDiscrete-Time (DT) signals: x[n], n—integer values only