Principles of Communications Flashcards
1
Q
Theories of Human Communication
A
Shannon-Weaver Theory and Roman Jacobson Theory
2
Q
The process that takes place in transmitter
A
Encoding, Compression and error-correcting operations, modulation process
3
Q
ELF
A
3-30 Hz
4
Q
SLF
A
30-300 Hz
5
Q
ULF
A
300-3000Hz
6
Q
VLF
A
3-30 kHz
7
Q
LF
A
30-300 kHz
8
Q
MF
A
300-3000 kHz
9
Q
HF
A
3-30 MHz
10
Q
VHF
A
30-300 MHz
11
Q
UHF
A
300-3000 MHz
12
Q
SHF
A
3-30 GHz
13
Q
EHF
A
30-300 GHz
14
Q
Wavelength Formula
A
Lambda=Vp/f
Vp=velocity of propagation
F=frequency
15
Q
Bandwidth Formula
A
f2-f1=fr/Q f2=upper cut-off frequency, Hz f1=lower cut-off frequency, Hz fr=resonant frequency, Hz Q=quality factor
16
Q
What is the unit of information?
A
Binary digit (bit)
17
Q
Formula of amount of information
A
I=log2(n)
Where n=number of coding levels
18
Q
Who founded the information theory?
A
Claude E. Shannon, 1948
19
Q
Hartley’s Law
A
C=2BWlog2(n)
20
Q
Shannon-Hartley theorem
A
C=BWlog2(1+S/N)
Note: S/N in abosolute value, not in Db
21
Q
Total Information Sent
A
H=Ct
H=bits
C=channel capacity
T=time in seconds
22
Q
Signal (or noise) Power
A
P=I^2R
23
Q
Power Required to send Information
A
Pn/P2=(n-1)^2
24
Q
It is introduced in the transmitting medium or channel
A
External Noise
25
Noise that normally occurs at 600 MHz
Industrial or Man-made Noise
26
Sources of Industrial or Man-made noise
Fluorescent lights, ignition systems of engines, switching equipment, commutator of electric motors, leakage from high voltage transmission lines
27
Usually caused by lightning discharges
Atmospheric Noise
28
Atmospheric Noise level formula
Fa=En-20logf+65.5, dB
En=rms noise field strength in a 1kHz bandwidth in dB above 1uV/m
F=frequency in MHz
29
The range of frequency of space noise
8MHz-1.5GHz
30
Sources of Extraterrestrial/Space noise
Sun(solar Noise)
Stars(cosmic Noise)
Galaxies(galactic Noise)
31
What is the year cycle of Corona flares and sunspots?
11 year
32
Antenna Noise Temperature
Ta=0.82Tmain+0.13(Tside-Te)
Tmain=sky brightness temperature within main lobe
Tside= sky brightness temperature within side lobe
Te=effective temperature of earth (290K)
33
It is produced and introduced at the receiver by the components that make up the receiver like resistors, diodes, transistors and even wires
Internal noise
34
What is the primary source of thermal noise?
The rapid and random motion of charge carriers inside a resistive component when heated
35
RMS noise voltage formula
```
Vn=sqrt(4BkRT) mnemonics:For BrookerT
K=boltzman constant (calcu constant 25)
T=temperature in Kelvin
B=Bandwidth
R=resistive component
```
36
Maximum available noise power formula
N=kTB, watts
37
It is caused by random fluctuations of electric current in an electric conductor, due to the fact that current is carried by discrete charges
Shot Noise
38
It is caused by random variations in the arrival of electrons or holes at the output of an amplifying device
Shot effect
39
Shot noise formula for temperature-limited vaccum-tube diode
I=current, A
B=bandwidth, Hz
Q=electrical charge, C (calc constant 23)
40
Shot noise for PN-Junction semiconductor diode
In=sqrt(2(Idc+2Is)qB)
Idc=Is(e^(qv/kT)-1)
Idc=direct diode current
Is=reverse saturation current
41
It is Caused by transit-time effect
Transit-time Noise
42
What is transit-time effect?
The time taken by an electron from the emitter to the collector. It has greater effect on microwave region
43
Noise found at the low audio frequency in transistors
Flicker Noise
44
Other terms of flicker noise
Modulation noise, excess noise, a/f noise or pink noise
45
It occurs whenever current is divided between two electrodes and results to random fluctuations
Partition Noise
46
Noise that appears as a series of bursts at two or more level. Also called as popcorn noise
Burst Noise
47
It is a large noise spike present in the avalanche current due to oscillation
Avalanche Noise
48
Equivalent Noise Resistance
Req=R1+R2/G1+R3/G1G2+R4/G1G2G3…
| G=power gain == A^2
49
Signal to Noise Ratio formulas
S/N=Signal Power/ Noise Power
| S/N(decibels)=10log(Ps/Pn)=20log(Vs/Vn)
50
What is the satisfactory telephone service S/N
30Db OR 1000
51
What is the satisfactory S/N for video and data?
45/15 decibels respectively
52
It is used to specify how noisy a device is.
Noise factor
53
Noise Factor Formula
NF=(S/N input)/(S/N output)
54
Noise Figure formula
10log(NoiseFactor)
55
Equivalent Noise Temperature Formula
Te=To(NF-1)
Te=equivalent noise temperature, K
To=reference Temperature, 290 K
NF=Noise Factor
56
Excess Noise Ratio
10log((Th-Tc)/Tc)
57
Friis’ Formula for overall noise factor
NF=NF1+(NF2-1)/G1+(NF3-1)/G1G2…
58
Friis’ Formula for overall noise Temperature
Te=Te1+(Te2)/G1+(Te3-1)/G1G2…
59
Total Noise power output formula
No=Gtk(T+Te)BW
60
Collection of offending sounds to which humans are involuntary exposed. This type of noise is usually referred to as noise pollution
Environmental Noise
61
In broadcast systems, it refers to the residual low level sound that is heard in quiet periods of the program/ unwanted residual electronic noise signal
Audio Noise
62
The inference picked up between transmitter and receiver output, often refered to as static
Radio Noise
63
The random dot pattern superimposed on the picture as a result of electric noise
Video Noise
64
A signal with flat frequency spectrum in linear space. It has the same power in any linear band
White Noise
| Same power in 40-60 Hz as with 4000-4020Hz
65
It has a flat frequency response in the logarithmic space
Pink noise
| Same power from 40-60Hz as with 4000-6000Hz
66
It is similar to pink noise but with a power density decrease of 6dB per octave with increasing frequency
Brown or red Noise
67
Noise wherein its power density increases 3dB per octave with increasing frequency
Blue (or Azure) Noise
68
Noise where its power density increases 6dB per octave with increasing frequency
Purple or violet noise
69
It is a noise subjected to a psychoacoustic equal loudness curve
Grey Noise
70
It is supposedly the background noise of the world
Green Noise
71
ITU designation of double sideband full carrier
A3E
72
ITU designation of Single Sideband reduced carrier
R3E
73
ITU designation of Single Sideband Full Carrier
H3E
74
ITU designation of Single Sideband suppressed carrier
J3E
75
ITU designation of independent sideband emission
B8E
76
ITU designation of Vestigial sideband
C3F
77
It is a system of modulation in which the amplitude of the carrier is mode proportional to the instantaneous amplitude of the modulating voltage
Amplitude modulation
78
He invented the radio that could transmit telegraph code
Guglielmo Marconi
79
AM Carrier signal equation
ec=Ec*sin(ωt+θ) or Ec*sin(2πf+θ)
80
AM modulating signal equation
Em=Em*sin(ωmt)=Em*sin(2*π*f)
81
Peak amplitude of the AM wave
E = Ec + Em = Ec + Emsin(ωmt)
82
Instantaneous amplitude of AM wave
e = Esin(ωct) = [Ec + Emsin(ωmt)]sin(ωmt)
83
It is a measure of the degree of modulation
Modulation Index (m)
84
Modulation Index formula
m = Em/ Ec = (Emax-Emin)/(Emax+Emin)
85
Modulation Index formula in terms of current
m = √(2(Iᵣ²-1))
Iᵣ = It/Ic
86
Modulation by several modulating signals
mt = √(m₁²+m₂²+...+mn²)
87
Percent modulation formula
```
%M = Em/Ec * 100%
%M = m * 100%
%M = [(Emax - Emin)/(Emax + Emin)]*100%
```
88
A form of interference produced from the distortion when m>1
Sideband Splatter
89
Formula for side-frequency amplitude
Esf = mEc/2
90
Required AM bandwidth formula
BW = USF - LSF = (fc + fm) - (fc - fm) = 2fm
91
Total power of AM signal
```
Pt = Pc + Plsb + Pusb
Pt = Pc*(1+m²/2)
```
Plsb = Pusb = m²Pc/2
92
Carrier power formula
Pc= Ec²/2R
```
Ec = Peak amplitude of the carrier wave
R = load impedance
```
93
Total AM voltage formula
Vt = Vc√(1+m²/2)
94
Total AM current formula
It = It√(1+m²/2)
95
A nonlinear device most likely used to combine signals to generate an AM signal since it offers gain.
Transistors
96
The simplest and most effective nonlinear device used to detect AM signal
Diode
97
The first rectifying demodulator that uses crystals that are metallic such as galena, iron pyrites and carborundum.
Crystal Detector
98
A thin pointed wire pressed against the surface of the crystal of a crystal detector
Cat Whisker
99
The type of detector using amplifying devices like transistors in place of ordinary diodes to provide both rectification and amplification at the same time
Power Detector
100
Has a better sensitivity than the diode detector that consists of a tuned circuit, a rectifier and RC low pass filter for recovery of the modulating signal
Grid-Leak Detector
101
An AM detector that uses a tickler coil which generates energy from the plate circuit into the grid circuit of the triode
Regenerative Detector
102
It is an oscillating regenerative detector
Autodyne
103
A device that generates high frequency power by means of a suitable antenna and is radiated through space or other mediums
Transmitter
104
The combination of a transmitter and a receiver
Radio System
105
An AM transmitter produced by feeding the output from an audio amplifier to a transformer whose secondary is in series with the supply line feeding the RF oscillator
Low Level Modulation
106
An AM transmitter produced by feeding the output from an audio amplifier to a transformer whose secondary is in series with the supply line feeding the power amplifier
High Level Modulation
107
Simplest form of AM
Modulated Carrier Wave
108
Consists of keying the modulator with a fixed AF tone
Class A2 Transmission
109
Modulating a transmitter with voice or other frequencies in amplitude
Class A3 Transmission
110
A device intended to receive a radio signal and extract the information or intelligence from RF signal
Radio Receiver
111
A receiver composed of several tuned radio-frequency amplifiers followed by circuits to detect and amplify the audio signal
Tuned Radio Frequency (TRF)
112
A receiver where all signal frequencies are converted typically to a constant lower frequency before detection.
Superheterodyne Receiver
113
The ability of the receiver to receive the desired signal and reject all others
Selectivity
114
The ability of the receiver to amplify weak signals
Sensitivity
115
It is the ability of the receiver to faithfully reproduce the information
Fidelity
116
Receiver bandwidth formula
BW = fₒ/Q
```
fₒ = carrier frequency
Q = required quality factor to achieve the given bandwidth
```
117
Low-side injections
f = fₒ - fᵢ
fᵢ = receiver's intermediate frequency
= 455 kHz for AM receivers
= 10.7 MHz for FM receivers
118
High-side injections
f = fₒ +fᵢ
fᵢ = receiver's intermediate frequency
= 455 kHz for AM receivers
= 10.7 MHz for FM receivers
119
Shape Factor Formula
SF = BW (-60dB)/BW (-3dB)
BW (-60dB), bandwidth at 60 dB down from the maximum
BW (-3dB), bandwidth at 60 dB down from the maximum
120
Bandwidth improvement formula
BW(improvement) = BW(RF)/BW(IF)
121
Noise figure improvement formula
NF(improvement) = 10log(BWimprovement)
122
Image frequency formula
fsi = fs + 2fi
```
fs = desired signal frequency
fi = intermediate frequency
```
123
Image rejection ratio formula
```
IR = Asig / Aimage = √(1+Q²q²)
IR(dB) = 20log(Asig/Aimage) = 20 log √(1+Q²q²)
```
```
Q = quality factor of the tuned circuit
Asig = voltage gain at signal frequency
Aimage = voltage gain at image frequency
```
124
Image rejection for High Q circuit (Q≥10)
IR(dB)≈ 20log(Qρ)
125
Coupling coefficient of IF coupling by inductive or transformer coupling
k = φs/φp
```
φs= secondary flux
φp= primary flux
```
126
Mutual inductance of IF coupling by inductive or transformer coupling
M = k√(LsLp)
L = winding conductance
127
Spurious response formula
fsp = (m/n)fʟᴏ ± fi/n
```
fsp = spurious response frequency
fʟᴏ = Local Oscillator frequency
fi = intermediate frequency
m,n = any integers
```
128
A form of AM in which only one of the sidebands is transmitted thus saving carrier power and the power of the other sideband
Single Sideband Suppressed Carrier (SSBSC) or J3E
129
Methods for generating SSBSC
Filter Method
Phase Shift Method
Weaver Method
130
Employs a balanced modulaor to generate a double-sideband suppressed-carrier signal
Filter Method
131
A baseband signal is transformed into a pair of signals having a constant 90 deg phase relationship with one another at all frequencies
Phase Shift Method
132
A circuit that creates an in-phase and quadrature from a real signal
Hilbert Transformer
133
It mixes baseband signals downward in frequency so that the center of the desired passband is at dc or 0 Hz.
Weaver Method
134
Power in a sideband formula
Psʙ = (Pc*m²/4)
135
Q of SSB filter
Q = [fc√(antilog(dB/20))]/4∆f
```
fc = carrier or center frequency (Hz)
dB = suppression of the unwanted sidband
∆f = separation between the two sidebands
```
136
Sideband Suppression Formula
Sideband Suppression(dB) = 20 log (cot(Φ/2))
Φ = deviation from a perfect 90 degree phase shift
cot Φ = 1/tangent(Φ)
137
An AM single sideband mode which is used with some AM radio transmissions
Independent Sideband
| B8E
138
Modulates two different input signals - one on the upper sideband and one on the lower sideband.
Independent Sideband
139
A hybrid between double sideband and single sideband
Independent Sideband
140
A type of AM technique that encodes data by varying the amplitude of a single carrier frequency
Vestigial Sideband (C3F)
141
Made by removing portions of the redundant sidebands
Vestigial Sideband Signal
142
Amplitude Modulation type commonly used in TV broadcasting
Vestigial Sidband
143
A reduced carrier single-sideband emission.
Single-sideband, Reduced Carrier (SSBRC)
(R3E)
(=.=")
144
A full carrier single-sideband emission,
Single-sidebnand, Full Carrier (SSBFC)
(H3E)
*mind blown*
145
FM detector Sensitivity formula
k(subscript d) = Vₒ / δ
k(subscript d) = detector sensitivity in volts per Hertz
Vₒ = output voltage
δ = frequency deviation requered for the output voltage
146
Phase Locked Loop detector output voltage formula
Vₒ(peak) = δ / k(subscript f)
δ = deviation of the signal
k(subscript f) = VCO proportionality constant
147
Critical Coupling Factor formula
k(subscript c) = 1 / √(QpQs)
Qp and Qs = primary and secondary Q of a transformer
148
Optimum Coupling Frequencty formula
k(subscript opt) = 1.5 k(subscript c)
149
Bandwidth of a double-tuned amplifier formula
BW = k(subscript opt) fₒ = 1.5k(subscipt c)fₒ
150
Modulation technique which varies the phase angle of a high-frequency carrier signal in proportion with the instantaneous amplitude of a modulating signal.
Angle Modulation
151
Forms of Angle Modulation
Frequency Modulation
| Phase Modulation
152
And angle modulation method in which the frequency of the constant amplitude carrier signal is varied in proportion with the amplitude of the modulating signal
Frequency Modulation
153
An angle modulation method in which the phase of the constant amplitude carrier signal is varied in proportion with the amplitude of the modulating signal
Phase Modulation
154
It can be used to produce FM
Phase Modulation
155
The general expression of a phase-modulated wave
V(t) = Vc cos (2 π fc t + k₁ Vm cos (2 π fm t))
```
V(t) = PM wave voltage
Vc = Peak carrier amplitude
fc = carrier frequency
k₁ = deviation sensitivity of phase modulator
Vm = peak modulating signal amplitude
fm = modulating signal frequency
```
156
FM wave expression
V(t) = Vc cos (ωc t + (δ/fm)sin(ωm t))
```
δ = frequency deviation
ωc = 2 π fc
ωm = 2 π fm
```
157
For PM, phase deviation or modulation index formula
m = ∆θ = k₁ Vm
```
k₁ = deviation sensitivity of the PM modulator
Vm = peak modulating signal amplitude
```
158
For FM, phase deviation or modulation index formula
m = (k₂ Vm)/ fm
```
k₂ = deviation sensitivity of the FM modulator
Vm = Peak modulating signal amplitude
fm = modulating frequency
```
159
For PM, frequency deviation formula
δ = k₁ Vm fm
```
k₁ = deviation sensitivity of the PM waveform
Vm = peak modulating signal amplitude
fm = modulating signal frequency
```
160
For FM, frequency deviation formula
δ = k₂ Vm
k₂ = deviation sensitivity of FM waveform
161
Percent modulation formula for PM and FM
%M = δactual / δmax * 100%
```
δactual = actual frequency deviation of carrier signal
δmax = maximum frequency deviation
```
162
Deviation ratio formula for PM and FM
D.R. = δmax / fm(max)
```
δmax = maximum peak frequency deviation of the carrier signal
fm(max) = maximum modulating frequency
```
163
Total transmitted power for an angle-modulated waveform formula
Pt = (Vc)² / 2R
```
Vc = peak amplitude of the carrier signal
R = load resistance
```
164
Formula for the amplitude of any side-frequency component (Jn)
Jn(mf) = (X)*2*[ (1/n!) - X²/(1!(n+1)!) + X⁴/(2!(n+2)!) - X⁶/(3!(n+3)!) + .... ]
where,
X = (m subscript f)/2
165
It is used the number of significant sidebands
Bessel Table
166
Bandwidth requirement formula for Narrowband FM
BW ≅ 2fm
167
Bandwidth requirement formula for wideband FM
BW ≅ 2 δ
δ = peak frequency deviation
168
Bandwidth requirement formula using the bessel function table
BW = 2 (n fm)
```
n = number of significant sidebands
fm = modulating signal frequency
```
169
Bandwidth requirement formula using Carson's Rule
BW = 2 (δ + fm)
```
δ = peak frequency deviation
fm = modulating signal frequency
```
170
Maximum phase deviation due to an interfering single-frequency sinusoid
∆θ ≈ Vn / Vc
171
Maximum frequency deviation due to an interfering single-frequency sinusoid
δ ≈ (Vn / Vc) fn
fn = noise modulating frequency
172
An inserting effect where as long as there is a sufficient SNR at the input to the FM receiver, the FM system has substantially better noise performance than an AM system
Threshold Effect
173
Refers to the case of two co-channel or adjacent channel FM signals being received at the same time by an FM receiver
Capture Effect
174
Result of the capture effect
* Weaker signal is considered as interference, stronger signal is captured.
* If both signals are of equal strength, the receiver will switch back and forth between the two signals
175
A high-pass filter which increases the S/N ratio at the higher frequency ends of the FM signal
Pre-emphasis network
176
A low-pass filter that attenuates the high-frequency signals at the receiver after demodulation and restores the original amplitude-versus-frequency characteristics to the information signal
De-emphasis network
177
Methods to generate FM
* Varactor Diode Modulator
* Reactance Modulator
* Linear IC FM Modulator
178
A direct FM generator that uses a varactor diode to deviate the frequency of a crystal oscillator
Varactor Diode Modulator
179
A direct FM generator that uses and active device like JFET
Reactance Modulator
180
Generates a direct FM output waveform that is relatively stable, accurate, and directly proportional to the input modulating signal
Linear IC Modulator
181
Primary disadvantage of Linear IC FM modulator
* Low output power
| * Need for several additional external components for proper operation
182
Methods to generate PM
* Varactor Diode Modulator
| * Transistor Modulator
183
A PM generator that changes the instantaneous phase of the carrier by varying the phase angle of the impedance seen by the carrier
Varactor Diode Modulator
184
A PM generator that produces a phase shift in the carrier signal proportional to the information signal by varying the emitter-to-collector resistance of the device.
Transistor Modulator
185
A FM transmitter that uses a reactance modulator or a VCO to produce large frequency deviations.
Crosby Direct FM Transmitter
186
A transmitter that employs frequency multiplier circuits to increase the deviation to the maximum level used in transmission
Crosby Direct FM Transmitter
187
In the Crosby Direct FM Transmitter, it is used to compensate for the frequency drift of the modulator stage
AFC Loop
188
A wideband FM transmitter that uses a phase-locked-loop to achieve the same frequency stability from the VCO as in a crystal oscillator and generate a high-index wideband FM output signal.
Phase-Locked Loop Direct FM Transmitter
189
An indirect FM transmitter that produces an output waveform where the phase deviation is directly proportional to the modulating signal
Armstrong Transmitter
190
A circuit that reduces unwanted amplitude variations in an FM waveform by producing a constant amplitude output for all input signals above prescribed minimum input level
Basic FM Limiter Circuit
191
A frequency discriminator that converts FM to AM before demodulating the AM envelope with a conventional peak detector circuit
Slope Detector
192
Composed of two single-ended slope detectors connected in parallel and fed 180ᵒ out-of-phase
Balanced Slope Detector
193
A tuned-circuit frequency discriminator whose operation is similar to the balanced slope detector
Foster-Seeley Discriminator
194
An FM demodulator that provides an advantage of not requiring limiter circuit preceding it
Ratio Detector
195
An FM demodulator that involves the use of linear integrated circuits
Phase-Locked Loop Demodulator
196
An FM demodulator that extracts the original information signal from the composite IF waveform by multiplying two (90 - out of phase) quadrature signals.
Quadrature FM Demodulator
197
Applications for Angle Modulation
1. ) Commercial Radio Broadcasting
2. ) Television Sound Transmission
3. ) Two-way FM Radio
4. ) Mobile Telephone Service
5. ) Cellular Radio System
6. ) FM Microwave Radio Communications System
198
A modulation system where it is not possible to have a two-channel system with a left channel and a right channel transmitted simultaneously and independently
Stereo FM Transmission
199
The sum signal composed of 50-15000 Hz which modulates the carrier like in monaural transmission
L+R Signal
200
The difference signal translated to 23-53kHz before transmission in the transmitter's balanced modulator
L-R Signal
201
An optional signal which is transmitted alongside the L+R and L-R components
SCA Signal
| Subsidiary Communications Authorization
202
Advantages of Angle Modulation over Amplitude Modulation
- Noise immunity
- Signal-to-noise improvement
- Capture Effect
- Efficiency of utilized power
203
Disadvantages of Angle Modulation over Amplitude Modulation
- Wider Bandwidth for Transmission
| - Circuit Complexity and Cost
