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EST > Chapter - 1 Principles Of Communications > Flashcards

Chapter - 1 Principles Of Communications Flashcards

1
Q

It is the sending , processing and receiving information by Electrical or Electronic means

A

COMMUNICATION SYSTEM

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2
Q

Basic Communication System

A

Transmitter
Transmission Channel
Receiver

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3
Q

It is the source of information which must be delivered or transmitted to a particular destination over a channel

Converts signal to form more suitable for transmission

Performs ENCODING and MODULATION

A

Transmitter

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4
Q

Basic Transmitter Components

A

Modulator
Amplifier
Oscillator

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5
Q

It is the destination upon which information from the transmitter is delivered
It is a collection of electronic devices and circuits that accepts the transmitted signals from the trans.medium and coverts to original form

Performs DECODING and DEMODULATION

A

RECEIVER

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6
Q

Basic Receiver Components

A

Demodulator
Amplifier
Output devices
(Speaker,Monitor,Printer)

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7
Q

It is the path or mediun that the information Travels from the transmitter to the Receiver

ATTENUATION occurs at this point

A

Transmission Channel

Medium

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8
Q

Classification of Transmission Media

A

Guided Media -provide conduit
(Transline , Optical Fiber , Waveguide)

Unguided Media -through Air
(Free space , Earth’s Atmosphere)

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9
Q

It is electronic circuit which is capable of increasing the signal magnitude or amplitude without altering the signal waveform characteristics

A

Amplifier

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10
Q

Q Point of Class A amplifier , Efficiency , Conduction Angle

A

Active (Linear)
25% or 50%
360deg

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11
Q

Q Point of Class B amplifier , Efficiency , Conduction Angle

A

Cutoff
78.5%
180deg

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12
Q

Q Point of Class AB amplifier

A

A little above cut-off
Between A and B
180-359 deg

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13
Q

Q Point of Class C amplifier

A

Below Cut-off
More than 90%
Less than 180 deg

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14
Q

Produces a periodic waveform on its output with only DC Supply voltage as input

Non rotating device for producing AC

Can be taught as an amplifier

A

OSCILLATOR

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15
Q

Types of Oscillator

A 
LC - for HF
•Hartley - Tapped Coil
•Colpitts - Split Capacitor
•Clapp - additional Capacitor
•Armstrong -tickler coil (transformer)

RC - for LF
•Wien Bridge -lead-Lag Circuit
•Phase Shift Oscillator - Series of RC sections
•Crystal Oscillator

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16
Q

It is a Frequency Selective Circuit design to pass some frequency and reject others

A

Filter

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17
Q

Basic Type of Filter

A
  • Low pass-below cutoff
  • High pass-above cutoff
  • Bandpass -narrow range
  • Band reject -reject narrow range
  • All pass - all frequency equally
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18
Q

Effect has maximum Flatness response in pass band

A

Butterworth filter

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19
Q

Have extremely good selectivity

A

Chebyshev Filter

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20
Q

Produce even greater attenuation than chebyshev filter

A

Cauer Filter

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21
Q

Provide desired frequency response but have a constant time delay in the pass band

A

Bessel (thompson) Filter

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22
Q

The number of times a particular phenomenon occurs in a given period of time

A

Frequency

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23
Q

It is the time required for one complete cycle of a repetitive waveform
Reciprocal of Frequency

A

Period or Time

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24
Q

waves travel at characteristic speeds depending on the type of wave and the nature of the propagation of the medium

A

Propagation Velocity

Vp = Vf • C

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25
Q

Distance between two similar points

A

Wavelength

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26
Q

Defined as a single valued function of time that conveys information

A

SIGNAL

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27
Q

These are time varying voltages or currents that are continuously changing such as sine wave and cosine wave

A

ANALOG SIGNAL

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28
Q

These are voltages or currents that change in discrete steps or levels

A

DIGITAL SIGNAL

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29
Q

It is the process of extracting information from signal, conditioning a signal from subsequent use. Signal transformation or altering a signal structure

A

SIGNAL PROCESSING

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30
Q

Simply describe the Frequency Content of the Signal

A

SPECTRA

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31
Q

The Signal Amplitude is plotted against Time like Oscilloscope

A

Time Domain Representation

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32
Q

The signal is plotted against frequency like in a Spectrum Analyzer

A

Frequency Domain Representation

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33
Q

It is also known as -3db bandwidth or half power bandwidth. Which indicated portion of electromagnetic spectrum

A

Bandwidth

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34
Q

Bandwidth formula

A

B=F(upper)-F(lower)
F(upper) = fr+B/2
F(lower) =fr-B/2

fr=1/2pi(sqrtLC)

B(effective) = (pi/2)(B)

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35
Q

These are also known as cutoff points , breakup points, -3dbpoints

A

Half Power Points

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36
Q

Transmission Modes

A
  • Simplex - one way
  • Half-Duplex - two-way alternate
  • Full-Duplex - two-way Simultaneous
  • Full/Full Duplex - both direction at the same time but different station
  • Echoplex-more than half duplex but less that full duplex . Used in error detection scheme
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37
Q

Electromagnetic Spectrum Mnemonics

A

Every Very Very Loving Mom Has Very Understanding Son Except I

Inject V Until Xplosive Growth

VHS at 3:30 kasi ma galing

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38
Q

Electromagnetic Spectrum Designation is based on the

A

ITU-R V.431-6:

Nomenclature of the Frequency and Wavelength Bands Used in Telecommunication

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39
Q

Voice Frequency Range

A

300hz to 3khz

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40
Q

Audio Frequency Range

A

20hz to 20khz

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41
Q

Electronics Communication System uses frequencies from

A

VLF to Light Frequencies

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42
Q

Frequencies that lies between VLF to EHF commonly used in wireless communications systems

A

Radiowaves

43
Q

Secondary carrier that carry additional modulating signal and itself modulated onto the main carrier

A

Subcarrier

44
Q

Too long wavelength to be seen

45
Q

Too short wavelength to be seen

A

Ultraviolet

46
Q

A fundamental quantity representing the rate at which energy is used and it is more readily measurable since jt can be converted to heat

47
Q

One-tenth of a bel

48
Q

Decibel Computations

A 
Bel = log(p2/p1)
Pdb = 10log(p2/p1)
Pdb = 20log(v2/v1)
        = 20log(I2/I1)
Pdbm = 10log(p/1mW) in mili
Pdbu =  10log(p/1uW) in micro
PdbW = 10log(p/1W) in Watt
49
Q

To convert dbu to dbm

A

Subtract 30

50
Q

To convert dbm to db

A

Subtract 30

51
Q

To convert dbu to db

A

Subtract 60

52
Q

To convert db to dbm

53
Q

To convert dbm to dbu

54
Q

To convert db to dbu

55
Q

Random , Undesirable Electrical Energy that enters the communication system via communicating medium and interferes with the transmitted message

56
Q

Is any waveform pertubatikn or deviation caused by imperfect response of the system to the desired signal

A

Distortion

57
Q

Any contamination by extraneous or external signals from human sources

A

Interference

58
Q

Two main Types of Noise

A

Uncorrelated and Correlated Noise

59
Q

Noise is present regardless of wether there is signal present or not

A

Uncorrelated Noise

60
Q

Noise is only present when there is a signal

A

Correlated Noise

61
Q

Two Main Types of Uncorrelated Noise

A

External and Internal Noise

62
Q

Noise coming from outside the environment

A

External Noise

63
Q

Also known as Static Noise , caused by lightning discharges

A

Atmospheric Noise

64
Q

Consist of electrical signals that originate from outside earth also know as space or deep space noise

A

Extraterrestrial Noise

65
Q

It is generated directly from the sun’s heat repeats every 11 years like corona and sunspots

A

Solar Noise

66
Q

Also known as sky noise , stellar noise or black body noise . It is RF noise generated by distant stars

A

Cosmic Noise

67
Q

It is noise other than solar noise and cosmic noise

A

Galactic Noise

68
Q

It is also known as man made noise usually between 1-600mhz

A

Industrial Noise

69
Q

It is an electrical noise generated within a device or circuit

A

Internal Noise

70
Q

Noise associated with random movement of electrons within a conductor

Brown si johnson White si gaussian

A

Thermal Noise

71
Q

Noise Power

72
Q

Noise Voltage

A

Vn = sqrt 4kTBR

73
Q

Total noise Voltage and Current and Power

A

Vnt = sqrt (vn1^2 + vn2^2)

Int = sqrt (in1^2 + in2^2)

Pt = P1 + P2 ….

74
Q

Random arrival of carriers (holes and electrons) happens in semiconductor

A

Shot Noise

75
Q

Noise Current

A

In = sqrt(2qBI)

In = sqrt(2qB(I+2Is))

76
Q

Also Known as Transistor Noise since it is commonly found in Transistors

A

Partition Noise

77
Q

Also Known as Modulation Noise , Flicker Noise , 1/f Noise. Noise Power varies inversely with frequency .

Also known as pink noise and it is common in low frequencies

A

Excess Noise

78
Q

It is an irregular,random variation produced by any modification to a stream pf carriers as they pass from input to output also known as HighFrequency Noise

A

Transit Time Noise

79
Q

Also known as Popcorn Noise which is a low frequency noise found in transistors such as BJTs

A

Burst Noise

80
Q

These are large noise spikes present in the avalanche current due to oscillation that result in the avalanching region

A

Avalanche Noise

81
Q

Type of noise having a flat spectrum over a defined frequency band

A

White noise

82
Q

Noise having a power density that decreases by 3 db per octave

A

Pink Noise

83
Q

Noise having a power density that decreases by 6db per octave

A

Brown or Red Noise

84
Q

Noise having a power density that increases by 3db per octave

A

Blue Noise

85
Q

Noise having a power density that increases by 6db per octave

A

Violet Noise

86
Q

It is a noise that sounds the same to the ears regardless of the frequency

A

Gray Noise

87
Q

Clashing , displeasing noise

A

Orange Noise

88
Q

Background noises of the world

A

Green Noise

89
Q

It is a silent noise

A

Black Noise

90
Q

Types of Correlated Noise

A

Harmonic Distortion
Intermodulation Distortion
Impulse Noise

91
Q

It is also known as Amplitude Distortion

A

Harmonic Distortion

92
Q

Power of a Signal Having Distortion

A

P=Po(1+THD^2)

THD = total harmonic distortion , unitless

93
Q

Unwanted sum and difference of frequencies when two or more signals are amplified by a non-linear device

A

Intermodulation Distortion

94
Q

It consist of sudden burst of irregularly shaped pulses characterized by High Amplitude peaks of Short Duration in the total noise spectrum

A

Impulse Noise

95
Q

Occurs when information signals from one source produce frequencies that falls outside their allocated bandwidth and interfere with another source

A

Interference

96
Q

It is the ratio of the signal power level to the noise power and it is used to determine the degree of intelligibility of a received signal of a certain system

A

Signal to Noise Power Ratio

S/N = Ps/Pn 
S/N = 10log(Ps/Pn)
97
Q

3 Figure of Merit

A
  • Noise Factor
  • Noise Figure
  • Equivalent Noise Temperature
98
Q

It is a figure of merit used to indicate how much signal to noise ratio deteriorates as signals passes through a circuit of series of circuits

A

Noise Factor

F= S/N(input)/S/N(output)

99
Q

Noise Factor Expressed in decibel

A

Noise Figure

NF=10log(F)

100
Q

It indicate the reduction in the sigbal to noise ratio a signal undergoes as it propagates through a receiver

A

Equivalent Noise Temperature

Teq = Ta(F-1)

Ta=290Kelvin (17deg Celsius)

101
Q

Total Gain in Cascaded Systems

A

Gt=G1xG2xG3……Gn

Gt(db) = G1db+G2db+G3db…+Gndb

102
Q

Equivalent Noise Temperature Referred to the Input

A

Teqt=Teq1+(Teq2/G1)+(Teq3/G1G2)+…….

103
Q

Noise Factor at the Output (friss formula)

A

Ft = F1+(F2-1/G1)+(F3-1/G1G2)+…….

104
Q

Equivalent Noise Resistance

A

Req=R1+(R2/G1^2)+(R3/G1^2G2^2)+……

EST (3 decks)

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