Chapter 1: Introduction to Electronic Communications by Wayne Tomasi - Review Notes

Reviewer and summary notes of the important concepts and formulas in Chapter 1 of the book "Introduction to Electronics Communications" by Wayne Tomasi.

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 telegraph.

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 installed

1876: Alexander Graham Bell and Thomas Watson Invented the telephone.

1877: Thomas Alva Edison invents the phonograph.

1880: Heinrich Hertz discovers electromagnetic waves.

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 users.

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 introduced.

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 launched.

1970: High-definition television (HDTV) introduced in Japan.

1977: First commercial use of optical fiber cables.

1983: Cellular telephone networks introduced in the United States.

1999: HDTV standards implemented in the United States.

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 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.



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 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 ________.



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 ( ITU)


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

Federal Communications Commission ( FCC )



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).




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

Emission Classifications


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 emission.

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 capacity.

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


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



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 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



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 )


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

Noise Factor ( F )


Noise Figure ( NF )




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 )

Complete List of Reviewers in Electronic Communications System per Chapter

Important List of Communications Engineering Materials

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