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Chapter 4

Signals

 Analog and Digital

Periodic and Aperiodic Signals

 Analog SignalsDigital Signals

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Analog and Digital

Information can be in the form of data, voice, picture, etc.

To be transmitted, information must be transformed into

media-transmittable signals.

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Analog and Digital

 Analog and digital clocks

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Analog and Digital

 Analog and digital signals  Analog signal – a continuous ave form that changes smoothl!

over time" as the ave moves from value A to value #, it passes

through and includes an infinite number of values along its path.

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Analog and Digital

 Analog and digital signals $cont% Digital signal – discrete" has limited number of defined values,

often as simple as & and '.

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Periodic and Aperiodic

Signals Aperiodic $non-periodic% Signals  An aperiodic signal has no repetitive pattern.

*an be decomposed into an infinite number of periodic signals.

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Analog Signals

Simple analog signals The sine ave is the most fundamental form of a periodic analog

signal.

Three characteristics of sine ave – amplitude,  period  or

frequency ,  phase

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Analog Signals

Simple analog signals $cont%  Amplitude – the value of the signal at an! point on the ave

+easured in volts $voltage%, amperes $current%, atts $poer%

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Analog Signals

Simple analog signals $cont% Period – the amount of time $in second% it takes a signal to

complete one c!cle $T%

re(uenc! – the number of c!cles per second $f% $in hert, %

f / &0T, T/ &0f 

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Digital Signals

Data can also be represented b! a digital signal & as a positive voltage and ' as ero voltage

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Digital Signals

#it interval $instead of period% Time re(uired to send one bit

#it rate $instead of fre(uenc!%

The number of bits sent in one second – bits per second$bps%

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Time and Frequency

DomainsTime-domain plot instantaneous amplitude ith respect to time

re(uenc!-domain plot  ma)imum amplitude ith respect to fre(uenc!

1)ample2

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Time and Frequency

Domains

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Composite Waveform

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Composite Signals

re(uenc! spectrum $of a signal% The combination of all sine ave signals that make up

that signal $shon using a fre(uenc!-domain graph%

#andidth $of a signal% The idth of the fre(uenc! spectrum

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Composite Signals

#andidth