Principles of Communications Flashcards
1
Q
it is the process of sending, processing and receiving information by electrical or electronic means
A
Communications System
2
Q
it refers to the basic process of exchanging information by - electronic means
A
Communications System
3
Q
1799 , Invented the electric Battery
A
Alessandro Volta
4
Q
1830 , He transmitted the first practical electrical signal over one mile of wire to activate electromagnet
A
Joseph Henry
5
Q
1837, He Invented the telegraph
A
Samuel Finley Breese Morse
6
Q
1843, He Invented the Facsimile
A
Alexander Bain
7
Q
1875, She designed a fixed-length binary code for telegraph
A
Emily Baudot
8
Q
1876 , He patented the telephone
A
Alexander Graham Bell
9
Q
1877 , He invented phonograph
A
Thomas Alva Edison
10
Q
1864 , He predicted mathematically radio propagation.
A
James Clerk Maxwell
11
Q
1880 , He patented the photophone
A
Alexander Graham Bell
12
Q
1887, He verified experimentally Maxwell’s Theory
A
Heinrich Hertz
13
Q
1888, He invented Liquid Crystal
A
Friedrich Reinitzer
14
Q
1895, He demonstrated Wireless Transmission
A
Guglielmo Marconi
15
Q
1906, He invents Amplitude Modulation (AM)
A
Reginald Fessenden
16
Q
1920, Radio Station _____ Broadcasts the first regular licensed AM radio transmission
A
KDKA
17
Q
1927, he produced the first all-electronic television transmission
A
Philo Farnsworth
18
Q
1930, He was the first to transmit images through a single glass fiber
A
Heinrich Lamm
19
Q
1933, He invented invented FM (Frequency Modulation) radio
A
Major Edwin Armstrong
20
Q
1937 , He Invented binary coded pulse-code modulation
A
Alec Reeves
21
Q
1946, They inaugurated the first mobile telephone system for the public known as mobile telephone system
A
AT & T ( American Telephone and Telegrap Company )
22
Q
1947, they developed the concept of cellular telephony but the technology to realized the concept did not yet exist
A
AT & T
23
Q
1954 , They announced imaging bundles, which propelled the fiber optics revolution and led to the development of flexible fiberscope
A
Abraham Van Heel, Harold Hopkins, Narinder Kapany
24
Q
1957, Russia Launched the world’s first artificial satellite named
A
Sputnik I
25
1962, NASA launches its first artificial satellite named
Telstar
26
1970, HDTV(high-definition Tv) was introduced in
Japan
27
1972 , they invented the TCP ( Transmission Control Protocol )
Bob Kahn and Vint Cerf
28
1973, he invents Ethernet to wire local computers together
Robert Metacalfe
29
1973, He invented the first practical mobile phone
Martin Cooper of Motorola
30
1983, they opened the first commercial cellular telephone system in the United States
AT & T
31
1991, He invents the WWW (World Wide Web)
Tim Burners-Lee
32
1996, First Smartphones
BlackBerry, Nokia and Palm
33
It is the source of information, which must be delivered or transmitted to a particular destination over a channel.
It is a collection of one or more electronic devices or circuits that converts the original source information to a form more suitable for transmission
performs encoding and modulation
Transmitter
34
Three Basic Transmitter Components
Modulator (modulates the signal)
Amplifier (provides power to the signal)
Oscillator(provides the carrier signal)
35
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 transmission medium and then converts those signals back to their original form
performs decoding and demodulation
Receiver
36
Three Basic Receiver Components
Demodulator or Detector (demodulates the signal)
Amplifiers (it provides power to the signal)
Output Devices (such as speakers,monitor,printer etc).
37
it is the path or medium that the information travels from the transmitter to the receiver(i.e it provides a means of transporting signals between a transmitter and a receiver).
Attenuation ( sometimes referred to as power loss) occurs at this point.)
Transmission Medium or Transmission Channel
38
Two Classifications of Transmission Media
Guided Media ( Wired ) - in a form of conduit
-Trasmission lines (Twisted Pairs , Twin Lead , Open-Wire Lines, Coaxial Cables, etc.)
Unguided Media (Wireless) - radiated through air or vacuum
-Free Space
-Earth's Atmosphere
39
it is an electronic circuit which is capable of increasing the signal magnitude or amplitude without appreciably altering the signal waveform characteristics.
Amplifier
40
active amplifier with a maximum efficiency of 25 or 50% and a conduction angle of 360 degrees and the distortion is Low
Class A Amplifier
41
cut-off amplifier with a maximum efficiency of 75% and a conduction angle of 180 degrees and the distortion is High
Class B Amplifier
42
a little above cut-off region with a maximum efficiency between class A and class B and a conduction angle between 180 to 359 degrees and the distortion is moderate
Class AB
43
Below Cut-off region amplifier with a maximum efficiency of more that 90% and a conduction angle of less than 180 and the distortion is Very High
Class C
44
It is a circuit that produces a periodic waveform on its output with only DC supply voltage as an input.
It is a non-rotating device for producing alternating current, the output frequency of which is determined by the characteristics of the device
It can be thought as an amplifier that provides itself ( through feedback ) with an input signal
Oscillator
45
Types of Oscillator
LC
RC
Crystal
46
type of oscillator commonly used at High Frequencies uses a parallel resonant circuit or tank circuit
LC Oscillator (Inductor,Resistor)
-Hartley Oscillator (uses tapped Coil)
-Colpitts Oscillator (uses split Capacitor)
-Clapp Oscillator (similar to colpitts with additional capacitor in series with the inductor)
-Armstrong Oscillator (uses tickler coil)
47
type of oscillator commonly used at Low Frequencies. provide regenerative feedback and to determine the frequency of operations
RC Oscillator (Resistor,Capacitor)
-Wien Bridge Oscillator (Utilize Lead-lag Circuit)
-Phase Shift Oscillator uses a series of RC Sections
48
type of oscillator usually used to produce an output which is highly stable and at a very precise frequency
Crystal Oscillator
49
It is a frequency-selective circuit which are designed to pass some frequencies and reject others
Filters
50
filters that constructed using resistor and capacitor or inductors and capacitors that do not amplify are called
Passive Filters
51
filters that uses RC networks with feedback in op-amp circuits, switched capacitor filters, crystal and ceramic filters , surface acoustic wave(SAW) filters and digital filters implemented with digital signal processing(DSP) techniques are called
Active Filters
52
Basic Types of Filter Circuits
Low-pass Filter (pass frequency below cutoff)
High-pass Filter(pass frequency above cutoff)
Bandpass Filter(pass frequency over a narrow range)
Band-reject Filter(reject frequencies over narrow range)
All-pass filter (passes all frequencies equally)
53
it is simply the number of times a particular phenomenon occurs in a given period of time.
Frequency
54
it may be number of voltage polarity alternations or electromagnetic field oscillations that takes place in a span of time; each alternation or oscillation is known as a
Cycle
55
frequency is measured in
cycle per second , or Hertz(hz) named after Heinrich Hertz, who was a pioneer in the field of electromagnetics.
56
Frequency Formula:
f = 1/Time (in second)
57
it is the time required for one complete cycle of a repetitive waveform, and it is known as the reciprocal of frequency
Period
58
Time Formula:
f = 1/Frequency (in Hertz)
59
waves travel at characteristic speeds depending on the type of wave and the nature of the propagation of the medium
electromagnetic wave velocity in the atmosphere or free space is approximately equal to the speed of light in vacuum
Velocity of Propagation
vp = vf * c
where:
vf = velocity factor , unitless
c = speed of light in a vacuum
c = 3x10^8 m/s
c = 186000 mi/s
60
it is the distance between two similar points of similar cycles of a periodic wave
the distance traveled by an electromagnetic wave during the time of one cycle
Wavelength (lambda)
lambda = c / f or = vp / f
where:
c = 3x10^8 m/s
f = frequency in hertz
vp = velocity of propagation m/s
61
it is defined as a single-valued function of time that conveys information(i,e for every instant of time there is a unique value of the function)
Signal
62
Two types of Signal
Analog Signal (Continous) Ex : sine wave
Digital Signal (Discrete) Ex: binary code
63
is the process of extracting information from a signal, conditioning a signal from subsequent use, signal transformation, or altering a signal structure.
Signal Processing
64
Simply describes the frequency content of the signal
Spectra
65
Two Types of Waveform Representation:
TDR - Time Domain Representation
FDR - Frequency Domain Representation
66
the signal amplitude is plotted against time like in a standard oscilloscope display
Time Domain Representation
67
the signal amplitude is plotted against frequency like in a spectrum analyzer
Frequency Domain Representation
68
It is also known as -3db bandwidth or half-power bandwidth which indicates the portion of the electromagnetic spectrum occupied by a signal.
Bandwidth - (Frequency Range)
69
Bandwidth Formula:
B = f(upper) - f(lower) or B(eff) = (pi/2)(B)
f(upper) = fr + B/2
f(lower) = fr - B/2
fr = (f(upper) + f(lower) / 2
where:
B= bandwidth, hz , B(eff) = effective bandwidth
fr = Resonant Frequency , hz
70
these are also known as cut-off points , breakup points and -3db points
Half - Power Points
71
Half Power points(-3db) :
Voltage, Current and Power :
V = 0.707Vmax
I = 0.707Imax
P = 0.5Vmax
72
Electromagnetic Spectrum Mnemonics:
Every, Very, Very, Loving, Mom, Has, Very, Understanding, Son, Except, I
Inject, Viagra, Until, Xplosive, Growth, of Cock
VHS at 3:30 kasi Ma Galing - (frequency ranges)
My kili-kili Has D Most Decent C Mill
73
Electronics Communications Systems uses frequecy ranges from
Very Low Frequency up to Light Frequencies
74
Radio waves are signals with frequencies that lies between _ to _ and commonly used in wireless communication systems
Very Low Frequency up to Extremely High Frequencies ,
75
it is the fundamental quantity representing the rate at which energy is used, and it is more readily measurable since it can be converted to heat
Power
76
it literally means one-tenth of a Bel, it is a logarithmic unit that can be used to measure ratio (not an absolute unit, but rather , it indicates the relation between two powers.)
Decibel
77
Decibel Computations :
Bel = log(P2/P1)
P(db) = 10log ( P2/P1 )
P(db) = 20log( V2/V1 )
P(db) = 20log( I2/I1 )
P(dbm) = 10log (P / 1mW)
P(dbu) = 10log (P / 1uW)
P(dbW) = 10log (P / 1W)
78
the Unit Neper defined in terms of natural logarithm is equivalent to
20 log (e) or 8.686 decibels
79
Gains are expressed in ______ decibels while Losses are expressed in _______ decibels
Gains (positive decibels)
Losses (negative decibels)
80
It is a random, unwanted , undesireable electrical energy that enters the communication system via the communicating medium and interferes with the transmitted message
Noise
81
is any waveform pertubation or deviation caused by the imperfect response of the system to the desired signal
Distortion
82
is any contamination by extraneous or external signals from human sources, other transmitters, power lines, machinery, switching circuits, etc.
Interference
83
it is a noise that is present regardless whether there is a signal present or not
Uncorrelated Noise
84
it is a noise that cannot be present in a circuit unless there is a signal
Correlated Noise
85
it is a type of noise that affects the communication system coming from the outside environment
External Noise
86
it is also known as Static Noise which is naturally occuring electrical disturbance that originates within Earth's atmosphere. It is caused by lightning discharges in thunderstorms and other natural electrical disturbances . it has very high peak-to-average power ratio and dominates at lower frequencies
Atmospheric Noise
87
it consist of electrical signals that originate from outside Earth's Atmosphere and is also known as Space or Deep-space Noise
Extraterrestrial Noise
88
it is generated directly from the sun's heat like in solar cycle every 11 years like corona and sunspots , it is more important at higher frequencies
Solar Noise
89
it is also known as Sky noise, Stellar noise or Black Body noise. it is an RF noise radiated by distant stars, and what they lack in nearness, they nearly makeup in numbers. it is also continously distributed throught the galaxies
Cosmic Noise
90
it is noise other than solar and cosmic noise
Galactic Noise
91
it is also known as man-made noise, since it is produced by mankind. usually between 1-600MHz usually most intense in industrial and densely populated areas
Industrial Noise
92
it is an electrical interference generated within a device or circuit
Internal Noise
93
it is associated with the rapid and random movement of electrons within a conductor due to thermal agitation. It is known as Brownian noise after its discoverer and also as Johnson Noise after the man related to Brownian particle movement of electron movement. it is also known as White Noise because of a random movement and also kwown as Gaussian Noise
Thermal Noise
94
Noise Power Formula:
Pn = kTB
k = Boltzmann's constant (shift 7 > 25)
B = Bandwidth, hz
T = Temperature in Kelvin
Kathryn Bernardo
Total Noise Power = Pn1 + Pn2 + ...
95
Noise Voltage Formula :
Vn = Sqrt(4kTBR)
R=Resistance
nag squirt ng apat na beses si Kathryn Bernardo
Total Noise Voltage and Current
= Sqrt (Vn1^2 + Vn2^2 + Vn3^2 + .... )
or
= Sqrt (In1^2 + In2^2 + In3^2 +... )
96
it is caused by the random arrival of carriers (holes and electrons) at the output element of an electronic device. it is due to random variations in current flow specifically in active devices such as tubes, transistors , semiconductor diodes, etc it is commonly found in devices with PN junctions
Shot Noise
97
Noise Current Formula In:
In = Sqrt ( 2qBI(dc) )
where :
q = 1.6x10^-19 C, electron charge in Coulomb (shift 7 > 23)
or
In = Sqrt( 2B (I(dc) + 2(I(s)) q )
where :
I(s) = reverse saturation current
98
it is also known as transistor noise since it is commonly found in transistors. it is similar to shot noise but occurs only in devices where singler current separates into two or more paths
Partition Noise
99
it is also known as Modulation noise ,Flicker noise or 1/f noise because its noise power varies inversely with frequency. it is also known as pink noise because there is more energy in low frequency end of the spectrum. used for testing and setting up audio systems
Excess Noise
100
it is an irregular, random variation produced by any modification to a stream of carriers as they pass from input to output of a device. its greates effect is in microwave region, and therefore also known as high frequency noise
Transit Time Noise
101
it is also known as popcorn noise which is a low frequency noise found in transistors such as BJTs . it appears as series of burst at two or more levels
Burst Noise
102
these are large noise spikes present in the avalanche current due to oscillation that result in the avalanching region
Avalanche Noise
