Chapter 1: Introduction to Electronic Communications – Tomasi Review

(Last Updated On: March 17, 2020)

Chapter 1: Introduction to Electronic Communications

This is the summary notes of the important concepts in Chapter 1 of the book “Introduction to Electronics Communications” by Wayne Tomasi. The notes are properly synchronized and concise for better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.







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


Electronic Communications Time Line
1830: American Scientist and professor Joseph
Henry transmitted the first practical electrical signal.
1837: Samuel Finley Breese Morse invented the
1843: Alexander Bain invented the facsimile.
1861: Johann Phillip Reis completed the first
nonworking telephone.
1864: James Clerk Maxwell released his
paper “Dynamic Theory of the Electromagnetic Field”, which concluded that
light electricity, and magnetism were related.
1865: Dr. Mahlon Loomis became the first person
to communicate wireless through the Earth’s atmosphere.
1866: First transatlantic telegraph cable was
1876: Alexander Graham Bell and Thomas Watson
Invented the telephone.
1877: Thomas Alva Edison invents the
1880: Heinrich Hertz discovers electromagnetic
1887: Heinrich Hertz discovers radio waves.
Marchese Guglielmo Marconi demonstrates wireless radio wave propagation.
1888: Heinrich Hertz detects and produces radio
waves. Heinrich Hertz conclusively proved Maxwell’s prediction that
electricity can travel in waves through the Earth’s atmosphere.
1894: Marchese Guglielmo Marconi builds his
first radio equipment, a device that rings a bell from 30 ft. away.
1895: Marchese Guglielmo Marconi discovered
ground wave propagation.
1898: Marchese Guglielmo Marconi established
the first radio link between England and France.
1900: American Scientist Reginald A. Fessenden
the world’s first radio broadcast using continuous waves.
1901: Marchese Guglielmo Marconi transmits
telegraphic radio messages from Cornwall, to Newfoundland. Reginald A.
Fessenden transmits the World’s first radio broadcast using continuous waves.
First successful transatlantic transmission of radio signal.
1903: Valdemar Poulsen patents an arc
transmission that generates continuous wave transmission 100-kHz signal that
is receivable 150 miles away.
1904: First radio transmission of music at
Graz, Austria.
1905: Marchese Guglielmo Marconi invents the
directional radio antenna.
1906: Reginald A. Fessenden invents amplitude
modulation (AM). First radio program of voice and music broadcasted in the
United States by Reginald Fessenden. Lee DeFrorest invents triode
(three-electrode) vacuum tube.
1907: Reginald Fessenden invents a high-
frequency Electric generator that produces radio waves with a frequency of
100 kHz.
1908: General Electric develops a 100-kHz, 2-kW
alternator for radio communications.
1910: The Radio Act of 1910 is the first
concurrence of government regulation of radio technology and services.
1912: The Radio Act of 1912 in the United
States brought order to the radio bands by requiring station and operator’s
licenses and assigning blocks of the frequency spectrum to the existing
1913: The cascade-tuning radio receiver and the
heterodyne receiver are introduced.
1914: Major Edwin Armstrong develops the
superheterodyne radio receiver.
1915: Vacuum-tube radio transmitters
1919: Shortwave radio is developed.
1920: Radio Station KDKA broadcasts the first
regular licensed radio transmission out of Pittsburgh, Pennsylvania.
1921: Radio Corporation of America (RCA) begins
operating Radio Central on Long Island. The American Radio League establishes
contact via shortwave radio with Paul Godley in Scotland, proving that
shortwave radio can be used for long distance communications.
1923: Vladimir Zworykin invents and
demonstrates television.
1927: A temporary five- member Federal Radio
Commission agency was created in the United States.
1928: Radio station WRNY in New York City
begins broadcasting television shows.
1931: Major Edwin Armstrong patents wide- band
frequency modulation (FM).
1934: Federal Communications Commission (FCC)
created to regulate telephone, radio, and television broadcasting.
1935: Commercial FM radio broadcasting begins
with monophonic transmission.
1937: Alec H. Reeves invents binary coded
pulse-code modulation. (PCM)
1939: National Broadcasting Company (NBC)
demonstrates television broadcasting. First use of two-way radio
communications using walkie-talkies.
1941: Columbia University Radio Club opens the
first regularly scheduled FM radio station.
1945: Television is born. FM moved from its
original home of 42 MHz to 50 MHz to 88 MHz to 108 MHz to make room.
1946: The American Telephone and Telegraph
Company (AT&T) inaugurated the first mobile telephone system for the
public called MTS (Mobile Telephone System).
1948: John Von Neumann created the first store
program electronic digital computer. Bell Telephone Laboratories unveiled the
transistor, a joint venture of scientist William Shockley, John Bardeen and
Walter Brattain.
1951: First transcontinental microwave system
began operation.
1952: Sony Corporation offers a miniature
transistor radio, one of the first mass produced consumer AM/FM radios.
1953: RCA and MBC broadcast first color
television transmission.
1954: The number of radio stations in the world
exceeds the number of newspapers printed daily.
1954: Texas Instruments becomes the first
company to commercially produce silicon transistors.
1956: First transatlantic telephone cable
systems began carrying calls.
1957: Russia launches the world’s first
satellite. (Sputnik)
1958: Kilby and Noyce develop first integrated
circuits. NASA launched the United States first satellite.
1961: FCC approves FM stereo broadcasting,
which spurs the development of FM. Citizens band (CB) radio first used.
1962: U.S. radio stations begin broadcasting
stereophonic sound.
1963: T1 (transmission 1) digital carrier
systems introduced.
1965: First commercial communications satellite
1970: High-definition television (HDTV) introduced
in Japan.
1977: First commercial use of optical fiber
1983: Cellular telephone networks introduced in
the United States.
1999: HDTV standards implemented in the United
1999: Digital Television (DTV) transmission
began in the United States.


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.



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

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.



The first commercial radio broadcasting station in 1920 that
broadcasted amplitude modulated signals in Pittsburgh.



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).



One-tenth of a decibel.



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.



Provides a means of transporting signals between a transmitter
and a receiver.

Transmission Medium


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.



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 ______.



The process of changing one or more properties of the analog
carrier in proportion with the information signal.



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

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

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



The reverse process of modulation and converts the modulated
carrier back to the original information.



Demodulation is performed in a receiver by a circuit called



2 Reasons why modulation is necessary in
electronic communications :

1. It is extremely difficult to radiate low-frequency signals
from an antenna in the form of electromagnetic energy.
2. 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.



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
_____________ .



The number of times a periodic motion, such as a sine wave of
voltage or current, occurs in a given period of time.



Each complete alternation of the waveform.



Is an international agency in control of allocating
frequencies and services within the overall frequency spectrum.

International Telecommunications Union (


In the United States, assigns frequencies and communications
services for free-space radio propagation.

Federal Communications Commission ( FCC )


Chapter 1: Introduction to Electronic Communications - Tomasi Review


Are signals in the 30Hz to 300Hz range and include ac power
distribution signals (60Hz) and low frequency telemetry signals.

Extremely Low
Frequencies ( ELF )


Are signals in the 300Hz to 3000Hz range and include
frequencies generally associated with human speech.

Voice Frequencies
( VF )


Are signals in the 3kHz to 30kHz range which include the upper
end of the human hearing range.

Very Low Frequencies
( VLF )


Are signals in the 30kHz to 300kHz range and are used
primarily for marine and aeronautical navigation.

Low Frequencies
( LF )


Are signals in the 300kHz to 3MHz range and are used primarily
for commercial AM radio broadcasting (535kHz-1605kHz).

Medium Frequencies
( MF )


Are signals in the 3MHz to 30MHz range and are often referred
to as short waves. Used for most two-way radio communications.

High Frequencies
( HF )


Are signals in the 30MHz to 300MHz range and are used for
mobile radio, marine and aeronautical communications, commercial FM
broadcasting (88 to 108 MHz) and commercial TV broadcasting of Ch 2 to 13
(54MHz to 216MHz).

Very High Frequencies
( VHF )


Are signals in the 300MHz to 3GHz range and are used by
commercial television broadcasting of channels 14 to 83, land mobile
communications services, cellular telephones, certain radar and navigation
systems, and microwave and satellite radio systems.

Ultrahigh Frequencies
( UHF )


Are signals in the 3GHz to 30GHz range and include the
majority of the frequencies used for microwave and satellite radio
communications systems.

Super High Frequencies
( SHF )


Are signals in the 30GHz to 300GHz range and are seldom used
for radio communications except in very sophisticated, expensive, and
specialized applications.

Extremely High Frequencies
( EHF )


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.



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 (i.e., the distance between similar points in a repetitive wave).



Chapter 1: Introduction to Electronic Communications - Tomasi Review


Radio transmitter classifications according to bandwidth,
modulation scheme, and type of information.

Emission Classifications


Chapter 1: Introduction to Electronic Communications - Tomasi Review
Ø The first symbol is a letter that designates the type of
modulation of the main carrier.
Ø The second symbol is a number that identifies the type of
Ø The third symbol is another letter that describes the type
of information being transmitted.


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.



The bandwidth of a communications channel is the difference
between the highest and lowest frequencies that the channel will allow to
pass through it.



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 1928, R. Hartley of Bell Telephone Laboratories developed a
useful relationship among bandwidth, transmission time, and information

Hartley’s Law
I µ B x t


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
Chapter 1: Introduction to Electronic Communications - Tomasi Review


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

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



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


Johnson proved that thermal noise power is proportional to the
product of bandwidth and temperature.

Noise Power


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


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 and also called the fundamental frequency.

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


Chapter 1: Introduction to Electronic Communications - Tomasi Review


A form of external noise and as the name implies it means to
disturb or detract form.



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


The ratio of the signal power level to the noise power level.

Signal-to-Noise Power Ratio ( S/N )
Chapter 1: Introduction to Electronic Communications - Tomasi Review


Figures of merit used to indicate how much the signal –
to-noise ratio deteriorates as a signal passes through a circuit or series of

Noise Factor ( F )
Noise Figure ( NF )


Chapter 1: Introduction to Electronic Communications - Tomasi Review


NF ( dB ) = 10 log F


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 )

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