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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