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SINGLE – SIDEBAND
COMMUNICATIONS SYSTEMS
CHAPTER 6
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A form of amplitude
modulation in which thecarrier is transmitted at full
power but only one of the
sidebands is transmitted.
AM Single-sideband FullCarrier
( SSBFC )
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A form of amplitude
modulation in which thecarrier is totally suppressed
and one of the sidebands
removed.
AM Single-sidebandSuppressed Carrier
( SSBSC )
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A form of amplitude modulation
in which one sideband is totally
removed and the carrier voltage
is reduced to approximately
10% of its unmodulatedamplitude.
AM Single-sidebandReduced Carrier
( SSBRC )
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It is the reinserted carrier inSSB! for demodulation
purposes.
Pilot Carrier
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A form of amplitude
modulation in which a singlecarrier fre"uency is
independently modulated by
two different modulating
signals.
AM Independent Sideband
( ISB )
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A form of amplitude
modulation in which thecarrier and one complete
sideband are transmitted# butonly part of the second
sideband is transmitted.
AM Vestigial Sideband
( VSB )
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$$$$ is the picture portion of
a commercial television
broadcasting signal.
VSB System
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Advantages of singlesideband
suppressed and reducedcarrier transmission over
conventional double sideband
fullcarrier transmission.
Bandidt! Conser"ation
and Poer #$$iciency
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&his ratio determines thedegree of intelligibility of a
received signal.
Signal-to-%oise Ratio
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'ith doublesideband
transmission# the two sidebandsand carrier may propagate
through the transmission media
by different paths and therefore#
experience different transmission
impairments.
Selecti"e Fading
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Sideband Fading
A condition in double
sideband transmission where
one sideband is significantly
attenuated.
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A form of selective fading where
there is a reduction of thecarrier level of a 100%
modulated wave that will ma(e
the carrier voltage less than the
vector sum of the two
sidebands.
Carrier-Amplitude Fading
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A condition where the relative
positions of the carrier andsideband vectors of the received
signal change# causing a decided
change in the shape of theenvelope# causing a severely
distorted demodulated signal.Carrier or Sideband
P!ase S!i$t
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A product modulator where the
output signal is the product ofthe modulating signal and the
carrier.
AM Modulator
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)odulator circuits that
inherently remove the carrierduring the modulation
process.
&SBSC Modulators
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A circuit that produces adoublesideband suppressed
carrier signal.
Balanced Modulator
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A balanced modulator that is
constructed with diodes andtransformers. Sometimes
called balanced latticemodulator.
Balanced Ring Modulator
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&he small carrier componentthat is always present in the
output signal of a balanced
modulator.
Carrier 'ea
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&he operation of this balanced
modulator as the balanced ring
modulator# is completely
dependent on the switching
action of diodes *1 through *+under the influence of the carrier
and modulating signal voltages.Balanced Bridge
Modulator
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A doublebalanced
modulator,demodulator thatproduces an output signal that
is proportional to the productof its input signals.
'M*+, .+/
Balanced Modulator IC
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&he circuit where the carrier isreinserted.
'inear Summer
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&hree methods for singlesideband generation.
Filter0 P!ase-S!i$t0 and
1!ird Met!od
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&ypes of singlesideband
filters.
Crystal 'attice0
Ceramic0
Mec!anical0
Sa Filters
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Mec!anical Filter
A mechanically resonant
transducer that receiveselectrical energy# converts it to
mechanical vibrations# and thenconverts the vibrations bac( to
electrical energy at its output.
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-ilters that use acoustic
energy rather than electromechanical energy to provide
excellent performance forprecise bandpass filtering.
Sur$ace Acoustic 2a"e
Filters
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eflected energy that cancelsand attenuates the incident
wave energy.
&estructi"e Inter$erence
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eflected energy that aids the
incident wave energy.
Constructi"e Inter$erence
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A transducer which launchesthe acoustic wave in only one
direction.
3nidirectional
1ransducer
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Any difference between the
transmit and receive localoscillator fre"uencies
produces a $$$$$$$ in thedemodulated information
signal.
Fre4uency 5$$set #rror
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-ifty hert or more offset is
distinguishable by a normallistener as a $$$$$$$.
1onal Variation
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A narrowband / that trac(s the
pilot carrier in the compositeSSB! receiver signal and uses
the recovered carrier to generate
coherent local oscillatorfre"uencies in the synthesier.
Carrier Reco"ery Circuit
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An SSB receiver that uses a
/ carrier recovery circuitand a fre"uency synthesier
to produce coherent local andbeat fre"uency oscillator
fre"uencies.
Multic!annel Pilto Carrier
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Systems that provide narrowband
voice communications for land
mobile services with nearly the
"uality achieved with -) systems
and do it using less than onethirdthe bandwidth.
Amplitude-CompandoringSingle-Sideband
( ACSSB )
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&he process of combining
transmissions from more thanone source and transmitting
them over a common facility#
such as metallic or optical fiber
cable or a radiofre"uency
channel.
Multiple6ing
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Single-SidebandSuppressed-Carrier
1ransmission
A transmission that can be used to
combine hundreds or even
thousands of narrowband channels
into single# composite wideband
channel without the channelsinterfering with each other.
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Singlesideband transmitters
are rated in $$$$$$$$ and $$$$$$$$.
Pea #n"elope Poer
( P#P ) 7Pea #n"elope Voltage
( P#V )
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