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CHAPTER 1
INTRODUCTION TO ELECTRONIC
COMMUNICATIONS
# DEFINITIONS TERMS
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. 183 7: 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 continous waves. 19 01: 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 operators licenses and assigning blocks of the frequency spectrum to the existing users.
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. 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 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 ) 24 A modulation technique where the information signal is analog and the phase () 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 () 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 )
In the United States, assigns frequencies and communications services for free-space radio propagation. Federal Communications Commission ( FCC )
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 108MHz) 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. 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 (i.e., the distance between similar points in a repetitive wave). Wavelength
ELECTROMAGNETIC WAVELENGTH SPECTRUM
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 1928, R. Hartley of Bell Telephone Laboratories developed a useful relationship among bandwidth, transmission time, and information capacity. Hartley’s Law I 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 OR
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 Noice
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. 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
The ratio of the signal power level to the noise power level. Signal-to-Noise Power Ratio ( S/N )
