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EST (Electronics System and Technologies) > Single-Sideband communications systems (Chapter 6) > Flashcards

Single-Sideband communications systems (Chapter 6) Flashcards

1
Q

AM Double-Sideband Communications Systems have two inherent disadvantages:

A
  1. Carrier power constitutes two-thirds or more of the total transmitted power
  2. it utilizes twice as much bandwidth needed with single-sideband systems
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2
Q

Single sideband was mathematically recognized and understood as early as _____

A

1914

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3
Q

Single sideband during _____ was the patent granted and a successful communications link established between _____ and _____

A

1923
England
United States

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4
Q

A form of amplitude modulation
in which the carrier is transmitted at full power but only one of the
sidebands is transmitted.

A

AM Single-sideband Full Carrier

SSBFC

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5
Q

SSBFC transmissions require only ____ as much bandwidth as conventional double-sideband AM.

A

1/2 or half

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6
Q

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.

A

80% or four-fifths

20% or one-fifths

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7
Q

For conventional double-sideband AM with 100% modulation, ____ of the total transmitted power is in the carrier and, _____ is in the sidebands.

A

67% or two-thirds

33% or one-third

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8
Q

SSBFC requires less bandwidth than DSBFC. True or False?

A

True

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9
Q

When the bandwidth is halved, what happens to the total noise power?

A

the noise power is halved

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10
Q

With SSBFC, the repetition rate of the envelope is ____ to the frequency of the modulating signal.

A

equal

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11
Q

With SSBFC, the depth of modulation is _____ to the amplitude of the modulating signal.

A

directly proportional

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12
Q

A form of amplitude modulation

in which the carrier is totally suppressed and one of the sidebands removed.

A

AM Single-sideband Suppressed

Carrier ( SSBSC )

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13
Q

SSBSC transmissions require only ____ as much bandwidth as conventional double-sideband AM.

A

half

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14
Q

In SSBSC with 100% modulation, the sideband power makes up to ____ of the total transmitted power

A

100%

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15
Q

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.

A

AM Single-sideband Reduced

Carrier ( SSBRC )

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16
Q

In SSBRC, _____ of the total power transmitted is in the unsuppressed sideband.

A

96%

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17
Q

To produce a reduced carrier component, the carrier is ______ during modulation and then ______ at a reduced amplitude.

A

totally suppressed

reinserted

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18
Q

SSBRC is often called as _____

A

single-sideband reinserted carrier

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19
Q

reinserted carrier is often called a ______ and is reinserted for demodulation purposes

A

pilot carrier

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20
Q

To demodulate a reduced carrier waveform with a conventional peak detector, the carrier must be ______, _______ and then ______ at a higher level in the receiver.

A

separated, amplified, reinserted

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21
Q

reduced carrier transmission is sometimes called ______

A

exalted carrier

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21
Q

Consequently, the signal-to-noise ratios for single and double sideband are ______

A

the same

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22
Q

In SSBRC, the carrier is transmitted at a ______ ,which also conserves power

A

reduced level

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23
Q

A form of amplitude modulation
in which a single carrier frequency is independently modulated by two
different modulating signals.

A

AM Independent Sideband ( ISB )

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24
It is a form of double-sideband transmission in which the transmitter consists of two independent single-sideband suppressed carrier modulators
ISB (Independent Sideband)
25
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
26
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 )
27
In VSB, the lower modulating-frequencies are transmitted _____, and the higher modulating-frequencies are transmitted _____
double-sideband | single-sideband
28
_____ system is the picture portion of a commercial television broadcasting signal, which is designated A5C by the FCC
VSB
29
It determines the degree of intelligibility of a received signal
signal-to-noise ratio
30
The three common AM transmissions systems:
Double-sideband full carrier (DSBFC) Double-sideband suppressed carrier (DSBSC) Single-sideband suppressed carrier (SSBSC)
31
the repetition rate of the DSBFC envelop is ______ to the modulating signal frequency
equal
32
The repetition rate of the DSBSC envelope is ______ the modulating signal frequency
equal to twice
33
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
34
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
35
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
0. 5 | 1. 5
36
Advantages of Single-Sideband transmission
Power conservation Bandwidth conservation Selective fading Noise reduction
37
Disadvantages of Single-sideband transmission
Complex receiver | Tuning difficulties
38
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
39
A condition in double-sideband | transmission where one sideband is significantly attenuated.
Sideband Fading
40
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
41
A product modulator where the | output signal is the product of the modulating signal and the carrier.
AM Modulator
42
Modulator circuits that | inherently remove the carrier during the modulation process.
DSBSC Modulators
43
A circuit that produces a | double-sideband suppressed-carrier signal.
Balanced Modulator
44
A balanced modulator that is constructed with diodes and transformers. Sometimes called balanced lattice modulator.
Balanced Ring Modulator
45
The small carrier component | that is always present in the output signal of a balanced modulator.
Carrier Leak
46
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
47
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
48
The circuit where the carrier | is reinserted.
Linear Summer
49
Three methods for | single-sideband generation.
Filter, Phase-Shift, and Third | Method
50
Types of single-sideband | filters.
Crystal Lattice, Ceramic, | Mechanical, Saw Filters
51
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
52
Filters that use acoustic energy rather than electro-mechanical energy to provide excellent performance for precise bandpass filtering.
Surface Acoustic Wave Filters
53
Reflected energy that cancels | and attenuates the incident wave energy.
Heterodyne
54
Reflected energy that aids the | incident wave energy.
Constructive Interference
55
A transducer which launches the | acoustic wave in only one direction.
Unidirectional Transducer
56
Any difference between the transmit and receive local oscillator frequencies produces a _______ in the demodulated information signal.
frequency offset error
57
Fifty hertz or more offset is | distinguishable by a normal listener as a _______.
tonal variation
58
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
59
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
60
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
61
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)
62
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)
63
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
64
Single-sideband transmitters | are rated in ________ and ________.
Peak Envelope Power ( PEP ) | & Peak Envelope Voltage ( PEV )

EST (Electronics System and Technologies) (4 decks)

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