Single-Sideband communications systems (Chapter 6) Flashcards
AM Double-Sideband Communications Systems have two inherent disadvantages:
- Carrier power constitutes two-thirds or more of the total transmitted power
- it utilizes twice as much bandwidth needed with single-sideband systems
Single sideband was mathematically recognized and understood as early as _____
1914
Single sideband during _____ was the patent granted and a successful communications link established between _____ and _____
1923
England
United States
A form of amplitude modulation
in which the carrier is transmitted at full power but only one of the
sidebands is transmitted.
AM Single-sideband Full Carrier
SSBFC
SSBFC transmissions require only ____ as much bandwidth as conventional double-sideband AM.
1/2 or half
In SSBFC, with 100% modulation, the carrier power (Pc) constitutes _____ of the total power transmitted (Pt) and only _____ of the total power is in the sideband.
80% or four-fifths
20% or one-fifths
For conventional double-sideband AM with 100% modulation, ____ of the total transmitted power is in the carrier and, _____ is in the sidebands.
67% or two-thirds
33% or one-third
SSBFC requires less bandwidth than DSBFC. True or False?
True
When the bandwidth is halved, what happens to the total noise power?
the noise power is halved
With SSBFC, the repetition rate of the envelope is ____ to the frequency of the modulating signal.
equal
With SSBFC, the depth of modulation is _____ to the amplitude of the modulating signal.
directly proportional
A form of amplitude modulation
in which the carrier is totally suppressed and one of the sidebands removed.
AM Single-sideband Suppressed
Carrier ( SSBSC )
SSBSC transmissions require only ____ as much bandwidth as conventional double-sideband AM.
half
In SSBSC with 100% modulation, the sideband power makes up to ____ of the total transmitted power
100%
A form of amplitude modulation
in which one sideband is totally removed and the carrier voltage is reduced
to approximately 10% of its unmodulated amplitude. Sometimes called
single-sideband reinserted carrier.
AM Single-sideband Reduced
Carrier ( SSBRC )
In SSBRC, _____ of the total power transmitted is in the unsuppressed sideband.
96%
To produce a reduced carrier component, the carrier is ______ during modulation and then ______ at a reduced amplitude.
totally suppressed
reinserted
SSBRC is often called as _____
single-sideband reinserted carrier
reinserted carrier is often called a ______ and is reinserted for demodulation purposes
pilot carrier
To demodulate a reduced carrier waveform with a conventional peak detector, the carrier must be ______, _______ and then ______ at a higher level in the receiver.
separated, amplified, reinserted
reduced carrier transmission is sometimes called ______
exalted carrier
Consequently, the signal-to-noise ratios for single and double sideband are ______
the same
In SSBRC, the carrier is transmitted at a ______ ,which also conserves power
reduced level
A form of amplitude modulation
in which a single carrier frequency is independently modulated by two
different modulating signals.
AM Independent Sideband ( ISB )
It is a form of double-sideband transmission in which the transmitter consists of two independent single-sideband suppressed carrier modulators
ISB (Independent Sideband)
ISB conserves both ______ and ______, as two information sources are transmitted within the same frequency spectrum, as would be required by a single source using conventional double- sideband transmission.
transmit power
bandwidth
A form of amplitude modulation
in which the carrier and one complete sideband are transmitted, but only part
of the second sideband is transmitted.
AM Vestigial Sideband ( VSB )
In VSB, the lower modulating-frequencies are transmitted _____, and the higher modulating-frequencies are transmitted _____
double-sideband
single-sideband
_____ system is the picture portion of a commercial television broadcasting signal, which is designated A5C by the FCC
VSB
It determines the degree of intelligibility of a received signal
signal-to-noise ratio
The three common AM transmissions systems:
Double-sideband full carrier (DSBFC)
Double-sideband suppressed carrier (DSBSC)
Single-sideband suppressed carrier (SSBSC)
the repetition rate of the DSBFC envelop is ______ to the modulating signal frequency
equal
The repetition rate of the DSBSC envelope is ______ the modulating signal frequency
equal to twice
The SSBSC waveform forms an envelope. True or false?
False
it is not a waveform but rather a single-frequency sinusoid equal in frequency to the unsuppressed sideband frequency
A conventional AM wave with 100% modulation contains ____ unit of carrier power and ____ unit of power in each sidebands for a total transmitted peak power of 1.5 units
1
0.25
A single sideband transmitter rated at ___ unit of power will produce a the same S/N ratio at the output of a receiver as ___ units of carrier plus sideband power from a double-sideband full-carrier signal
- 5
1. 5
Advantages of Single-Sideband transmission
Power conservation
Bandwidth conservation
Selective fading
Noise reduction
Disadvantages of Single-sideband transmission
Complex receiver
Tuning difficulties
With double-sideband
transmission, the two sidebands and carrier may propagate through the
transmission media by different paths and therefore, experience different
transmission impairments. This condition is called
Selective Fading
A condition in double-sideband
transmission where one sideband is significantly attenuated.
Sideband Fading
The most common and most serious form of selective fading
A condition where the relative
positions of the carrier and sideband vectors of the received signal change,
causing a decided change in the shape of the envelope, causing a severely
distorted demodulated signal.
carrier-amplitude fading
A product modulator where the
output signal is the product of the modulating signal and the carrier.
AM Modulator
Modulator circuits that
inherently remove the carrier during the modulation process.
DSBSC Modulators
A circuit that produces a
double-sideband suppressed-carrier signal.
Balanced Modulator
A balanced modulator that is
constructed with diodes and transformers. Sometimes called balanced lattice
modulator.
Balanced Ring Modulator
The small carrier component
that is always present in the output signal of a balanced modulator.
Carrier Leak
The operation of this balanced
modulator as the balanced ring modulator is completely dependent on the
switching action of diodes D1 through D4 under the influence of the carrier
and modulating signal voltages.
Balanced Bridge Modulator
A double-balanced
modulator/demodulator that produces an output signal that is proportional to
the product of its input signals.
LM1497 / 1596 Balanced
Modulator IC
The circuit where the carrier
is reinserted.
Linear Summer
Three methods for
single-sideband generation.
Filter, Phase-Shift, and Third
Method
Types of single-sideband
filters.
Crystal Lattice, Ceramic,
Mechanical, Saw Filters
A mechanically resonant
transducer that receives electrical energy, converts it to mechanical
vibrations, and then converts the vibrations back to electrical energy at its
output.
Mechanical Filter
Filters that use acoustic
energy rather than electro-mechanical energy to provide excellent performance
for precise bandpass filtering.
Surface Acoustic Wave Filters
Reflected energy that cancels
and attenuates the incident wave energy.
Heterodyne
Reflected energy that aids the
incident wave energy.
Constructive Interference
A transducer which launches the
acoustic wave in only one direction.
Unidirectional Transducer
Any difference between the
transmit and receive local oscillator frequencies produces a _______ in the
demodulated information signal.
frequency offset error
Fifty hertz or more offset is
distinguishable by a normal listener as a _______.
tonal variation
A narrowband PLL that tracks
the pilot carrier in the composite SSBRC receiver signal and uses the
recovered carrier to generate coherent local oscillator frequencies in the
synthesizer.
Carrier Recovery Circuit
An SSB receiver that uses a PLL
carrier recovery circuit and a frequency synthesizer to produce coherent
local and beat frequency oscillator frequencies.
Multichannel Pilot Carrier
Systems that provide narrowband
voice communications for land-mobile services with nearly the quality
achieved with FM systems and do it using less than one-third the bandwidth.
Amplitude-Compandoring Single-Sideband
ACSSB
It is the process of combining transmissions from more than one source and transmitting them over a common facility, such as metallic or optical fiber cable or a radio frequency channel
Frequency-Division Multiplexing (FDM)
It is a multiplexing method that uses double-sideband suppressed-carrier transmission to combine two information sources into a single composite waveform that is then transmitted over a common facility without the two channels interfering with each other
Quadrature Multiplexing (QM)
A transmission that can be used
to combine hundreds or even thousands of narrowband channels into single,
composite wideband channel without the channels interfering with each other.
Single-Sideband
Suppressed-Carrier Transmission
Single-sideband transmitters
are rated in ________ and ________.
Peak Envelope Power ( PEP )
& Peak Envelope Voltage ( PEV )
