Prelim Flashcards
Are time-varying voltages or currents that are continuously
changing such as sine and cosine waves.
analog signals
Is sometimes referred to as a power loss.
Attenuation
Is sometimes referred to as a ____________ , If Pout = Pin,
the absolute power gain is 1, and the dB power gain is 0 dB.
Unity Power Gain
Are voltages or currents that change in discrete steps or
levels.
digital signals
In 1876, Alexander Graham Bell and Thomas A. Watson were the
first to successfully transfer human conversation over a crude metallic- wire
communications systems using this device.
Telephone
The first commercial radio broadcasting station in 1920 that
broadcasted amplitude modulated signals in Pittsburgh.
KDKA
Is a logarithmic unit that can be used to measure ratio.
Decibel ( dB )
Is a unit of measurement used to indicate the ratio of a power
level with respect to a fixed reference level (1mW).
dBm
One-tenth of a decibel.
Bel
A collection of one or more electronic devices or circuits
that converts the original source information to a form more suitable for
transmission over a particular transmission medium.
Transmitter
Provides a means of transporting signals between a transmitter
and a receiver.
Transmission Medium
Its fundamental purpose is to transfer information from one
place to another.
Electronic Communication System
The transmission, reception, and processing of information
between two or more locations using electronic circuits.
Electronic Communication
A collection of electronic devices and circuits that accepts
the transmitted signals for the transmission medium and then converts those
signals back to their original form.
Receiver
Is any unwanted electrical signals that interfere with the
information signal.
System Noise
Because it is often impractical to propagate information
signals over standard transmission media, it is often necessary to modulate
the source information onto a higher-frequency analog signal called a
Carrier
The process of changing one or more properties of the analog
carrier in proportion with the information signal.
Modulation
A system in which energy is transmitted and received in analog
form (a continuously varying signals such as a sine wave).
Analog Communication System
A true digital system where digital pulses (discrete levels
such as +5V and ground) are transferred between two or more points in a
communications system.
Digital Transmission
The transmittal of digitally modulated analog carriers between
two or more points in a communications system.
digital radio
A modulation technique where the information signal is analog
and the amplitude (V) of the carrier is varied proportional to the
information signal.
Amplitude Modulation ( AM )
A modulation technique where the information signal is analog
and the frequency (f) of the carrier is varied proportional to the
information signal.
Frequency Modulation ( FM )
A modulation technique where the information signal is analog
and the phase (q) of the carrier is varied proportional to the information
signal.
Phase Modulation
A modulation technique where the information signal is digital
and that amplitude (V) of the carrier is varied proportional to the
information signal.
Amplitude Shift Keying ( ASK )
A modulation technique where the information signal is digital
and the frequency (f) of the carrier is varied proportional to the
information signal.
Frequency Shift Keying ( FSK )
A modulation technique where the information signal is digital
and the phase (q) of the carrier is varied proportional to the information
signal.
Phase Shift Keying
PSK
A modulation technique where both the amplitude and the phase
of the carrier are varied proportional to the information signal.
Quadrature Amplitude Modulation
QAM
Modulation is performed in a transmitter by a circuit called
Modulator
The reverse process of modulation and converts the modulated
carrier back to the original information.
Demodulation
Demodulation is performed in a receiver by a circuit called
Demodulator
2 Reasons why modulation is necessary in
electronic communications :
- It is extremely difficult to radiate low-frequency signals
from an antenna in the form of electromagnetic energy. - Information signals often occupy the same frequency band
and, if signals from two or more sources are transmitted at the same time,
they would interfere with each other.
A specific band of frequencies allocated a particular service.
Channel
Process of converting a frequency or band of frequencies to
another location in the total frequency spectrum.
Frequency Translation
The purpose of an electronic communications system is to
communicate information between two or more locations commonly called
Stations
The number of times a periodic motion, such as a sine wave of
voltage or current, occurs in a given period of time.
Frequency
Each complete alternation of the waveform.
Cycle
Is an international agency in control of allocating
frequencies and services within the overall frequency spectrum.
International Telecommunications Union (
ITU)
Are signals in the 0.3THz to 300THz range and are not
generally referred to as radio waves. Used in heat seeking guidance systems,
electronic photography, and astronomy.
Infrared
Includes electromagnetic frequencies that fall within the
visible range of humans (0.3PHz to 3PHz).
Visible Light
Used for optical fiber systems.
Light-wave Communications
The length that one cycle of an electromagnetic wave occupies
in space
Wavelength
Radio transmitter classifications according to bandwidth,
modulation scheme, and type of information.
Emission Classifications
The two most significant limitations on the performance of a
communications system are ________and ________.
Noise and Bandwidth
The difference between the highest and lowest frequencies
contained in the information.
Bandwidth
The bandwidth of a communications channel is the difference
between the highest and lowest frequencies that the channel will allow to
pass through it.
Passband
A highly theoretical study of the efficient use of bandwidth
to propagate information through electronic communications systems.
Information Theory
The measure of how much information can be propagated through
a communications system and is a function of bandwidth and transmission time.
Information Capacity
The most basic digital symbol used to represent information.
Binary Digit / Bit
The number of bits transmitted during one second and is
expressed in bits per second (bps).
Bit Rate
In 1948, mathematician Claude E. Shannon published a paper in
the Bell System Technical Journal relating the information capacity of a
communications channel to bandwidth and signal-to-noise ratio.
Shannon limit for information capacity
In 1948, mathematician Claude E. Shannon published a paper in
the Bell System Technical Journal relating the information capacity of a
communications channel to bandwidth and signal-to-noise ratio.
Shannon limit for information capacity
I = Blog2(1+S/N)
Shannon limit for information capacity
Any undesirable electrical energy that falls within the
passband of the signal.
Electrical Noise
Noise present regardless of whether there is a signal present
or not.
Uncorrelated Noise
Noise that is generated outside the device or circuit.
External Noise
Noise that is naturally occurring electrical disturbances that
originate within Earth’s atmosphere.
Atmospheric Noise
Atmospheric noise is commonly called
Static Electricity
Noise consists of electrical signals that originate from
outside Earth’s atmosphere and is sometimes called deep-space noise.
Extraterrestrial Noise
Extraterrestrial noise is sometimes called
Deep-Space Noise
Noise generated directly from the sun’s heat.
Solar Noise
Noise sources that are continuously distributed throughout the
galaxies.
Cosmic Noise
Noise that is produced by mankind.
Man-made Noise
Electrical interference generated within a device or circuit.
Internal Noise
Noise caused by the random arrival of carriers (holes and
electrons) at the output element of an electronic device.
Shot Noise
Any modification to a stream of carriers as they pass from the
input to the output of a device produces an irregular, random variations.
Transit-time Noise
Associated with the rapid and random movement of electrons
within a conductor due to thermal agitation
Thermal Noise
THERMAL AGITATION HAS SEVERAL NAMES,
INCLUDING :
Ø Thermal Noise, because it is temperature dependent;
Ø Brownian Noise, after its discoverer;
Ø Johnson Noise, after the man who related Brownian particle
movement of electron movement;
Ø White Noise, because the random movement is at all
frequencies;
Johnson proved that ___________ is proportional to the
product of bandwidth and temperature.
Noise Power
Noise Power Formula
N = KTB
A form of internal noise that is correlated (mutually related)
to the signal and cannot be present in a circuit unless there is a signal. “
no signal, no noise! “
Correlated Noise
Noise that is only present with the signal.
Correlated Noise
Occurs when unwanted harmonics of a signal are produced
through nonlinear amplification (nonlinear mixing).
Harmonic Distortion
The generation of unwanted sum and difference frequencies
produced when two or more signals mix in a nonlinear device.
Inter-modulation Distortion
The original signal is called
Fundamental Frequency
Fundamental Frequency is also called
First Harmonic
A frequency two times the original signal frequency.
Second Harmonic
A frequency three times the original signal frequency.
Third Harmonic
Another name for harmonic distortion.
Amplitude Distortion
Characterized by high-amplitude peaks of short duration in the
total noise spectrum.
Impulse Noise
A form of external noise and as the name implies it means to
disturb or detract form.
Interference
Noise produced when information signals from one source
produce frequencies that fall outside their allocated bandwidth and interfere
with information signals from another source.
Electrical interference
he ratio of the signal power level to the noise power level
Signal-to-Noise Power Ratio ( S/N )
Figures of merit used to indicate how much the signal –
to-noise ratio deteriorates as a signal passes through a circuit or series of
circuits (unitless)
Noise Factior (F)
Figures of merit used to indicate how much the signal –
to-noise ratio deteriorates as a signal passes through a circuit or series of
circuits (dB)
Noise Figure (NF)
Formula for Noise Figure (NF)
10logF
A convenient parameter often used rather than noise figure in
low noise, sophisticated VHF, UHF, microwave, and satellite radio receivers.
It indicates the reduction in the signal-to-noise ratio a signal undergoes as
it propagates through a receiver.
Equivalent Noise Temperature
( Te )
Te = T ( F – 1 )
Transfer information from one place to another
Electronic Communications System
Transmission, reception and processing of information between two or more locations using electronic circuits
Electronic Communications System
broadcast first licensed radio transmission
KDKA
Use to measure magnitude of earthquakes, intensity of acoustical signals, power ratios, voltage and current ratios, etc.
DECIBEL (dB)
A transmission-measuring unit used to express relative gains and losses of electronic devices and circuits
DECIBEL (dB)
The measurement unit of choice for virtually all EM frequency bands from ultralow frequencies to light-wave frequencies terminated in a variety of impedances
dBm
A process of changing one or more properties of an analog carrier in proportion with the information signal
Modulation and Demodulation
is an information signal that has been acted on by a carrier
MODULATED WAVE/MODULATED SIGNAL
Why do we need to MODULATE???
It is extremely difficult to radiate low-frequency signals from an antenna in the form of EM energy &
Information signals often occupy the same frequency band and if signals from two or more sources are transmitted at the same time, they would interfere with each other
Band Number and Designation of a 30 Hz to 300 Hz frequencies
BN: 2
Extremely Low Frequencies (ELF)
Band Number and Designation of a 0.3 kHz to 3 kHz frequencies
BN: 3 Voice Frequencies (VF)
Band Number and Designation of a 3 kHz to 30 kHz frequencies
BN: 4
Very Low Frequencies (VLF)
Band Number and Designation of a 30 kHz to 300 kHz frequencies
BN: 5
Low Frequencies
Band Number and Designation of 0.3 MHz to 3 MHz frequencies
BN: 6
Medium Frequencies
Band Number and Designation of 3MHz to 30 MHz frequencies
BN: 7
High Freqencies
30 MHz to 300 MHz
8
Very High Frequencies (VHF)
300 MHz to 3 GHz
9
Ultra High Frequencies (UHF)
3 GHz to 30 GHz
10
Super High Frequencies (SHF)
30 GHz to 300 GHz
11
Extremely High Frequencies (EHF)
Ambient Absolute Temperature (T)
290K
Friiss’ Formula
FT(Total Noise Factor) = F1 + (F2-1)/A1 + (F3-1)/A1A2 + … +(Fn-1)/A1A2…An
Noise Factor Formula
F = (inp SNR/outp SNR
Noise Figure Formula
NF = 10logF
