Electronic Communication Explained

Introduction to Electronic Communication

• Electronic communication involves sending, receiving, and processing information electrically.
• Methods of communication include face-to-face interaction, signals, written words, and electrical innovations like the telegraph, telephone, radio, television, and the Internet.
• Barriers to communication focus on language and geographical distance
• Contemporary communication emphasizes the accumulation, packaging, and exchange of information.

Electronic Communication

• Defined as sending, receiving, and processing information electrically.
• Information comes from symbols such as letters, numbers, words, and sounds, which are elements of an alphabet.
• Communication systems include radio, telephony, telegraph, broadcasting, radar, telemetry, and radio aids for navigation.

Electronic Communication Timeline

• 1830: Joseph Henry transmits the first practical electrical signal.
• 1837: Samuel Finley Breeze Morse invents the telegraph and patents it in 1844.
• 1843: Alexander Bain invents the facsimile.
• 1847: James Clerk Maxwell proposes the Electromagnetic Radiation Theory.
• 1860: Johann Philipp Reis produces a device called the Telephone, which transmits musical tones over a wire but cannot reproduce them.
• 1864: James Clerk Maxwell establishes the Theory of Radio or Electromagnetism.
• 1875: Thomas Alba Edison invents the Quadruplex telegraph and J. M. Emile Baudot invents the practical Multiplex Telegraph
• 1876: Alexander Graham Bell and Thomas A. Watson invent the telephone, capable of transmitting voice signals on March 10.
• 1877: Thomas Edison invents the Phonograph.
• 1878: Francis Blake invents the Microphone Transmitter using a platinum point bearing against a hard carbon surface.
• 1882: Nikola Tesla outlines the basic principles of radio transmission and reception.
• 1887: Heinrich Hertz detects electromagnetic waves with an oscillating circuit, establishing the existence of radio waves.
• 1889: Hertz discovers the progressive propagation of electromagnetic action.
• 1890: Almon Strowger introduces the dial-switching system for telephones
• 1895: Marchese Guglielmo Marconi discovers ground-wave radio signals.
• 1898: Guglielmo Marconi establishes the first radio link between England and France.
• 1901: Reginald A. Fessenden transmits the world's first radio broadcast using continuous waves.
• 1904: John Ambrose Fleming invents the Vacuum Tube Diode.
• 1906: Reginald Fessenden invents Amplitude Modulation (AM).
• 1906: Lee De Forest adds a grid to the diode and produces a triode.
• 1906: Ernst F. W. Alexanderson invents the Tuned Radio Frequency Receiver (TRF).
• 1907: Reginald Fessenden develops the Heterodyne Receiver.
• 1918: Edwin H. Armstrong invents the Superheterodyne Receiver.
• 1923: J. L. Baird and C. F. Jenkins demonstrate the transmission of Black and White Silhouettes in motion
• 1923: Vladymir Zworykin and Philo Farnsworth develop television cameras called the Iconoscope and Image Detector.
• 1928: The first practical television is invented.
• 1931: Edwin Armstrong invents Frequency Modulation, greatly improving signal quality.
• 1937: Alec Reeves invents Pulse Code Modulation for digital encoding of PCM signals.
• 1945: Arthur C. Clarke proposes the use of satellites for long distance radio transmissions.
• 1946: AT&T introduces the first mobile telephone system, MTS (Mobile Telephone System).
• 1947: John Bardeen, Walter Brattain, and William Shockley introduce bipolar junction transistors which started a new trend in radio receiver design on December 4.
• 1951: The first transcontinental microwave system begins operation.
• 1954: J. R. Pierce shows how satellites could orbit the earth and effect transmission with earth stations.
• 1957: Russia launches Sputnik I - the first active earth satellite.
• 1957: Troposcatter Radio Link is established between Florida and Cuba.
• 1958: Jack Kilby develops the first Monolithic Integrated Circuit Semiconductor chip.
• 1959: Robert Noyce invents the Very Large Scale Integrated Circuit (VLSIC).
• 1962: AT&T launches Telstar I, the first satellite to both receive and transmit signals simultaneously.
• 1965: COMSAT and INTELSAT launch the first communications satellite named Early Bird at approximately 34000 km above sea level.
• 1967: K. C. Kao and G. A. Bockam propose the use of cladded fiber cables as a new transmission medium.
• 1977: The first commercial use of optical fiber cables occurs.
• 1983: Cellular telephone networks introduced.
• 1991: Tim Berners-Lee develops the World Wide Web (WWW).

Elements of Communication Systems

• Basic components include the transmitter, channel or medium, receiver, and noise.
• A transmitter converts the electrical signal into a suitable signal for transmission over a given medium using oscillators, amplifiers, tuned circuits, filters, modulators, frequency mixers and synthesizers, and other circuits.
• A communication channel is the medium through which signals are sent, including electrical conductors, optical media, free space, and system-specific media.
• A receiver accepts the transmitted message, converts it into an understandable form, and contains amplifiers, oscillators, mixers, tuned circuits, filters, and a demodulator.
• A transceiver is an electronic unit incorporating circuits for both sending and receiving signals, for example telephones, fax machines, handheld CB radios, cell phones, and computer modems.
• Noise is random, undesirable energy that interferes with the transmitted message.
• Signal attenuation, or degradation, exists in all media of wireless transmission and is proportional to the square of the distance between the transmitter and receiver.

Types of Electronic Communication

• Classified as one-way (simplex) or two-way (full duplex or half duplex) transmissions.
• Can be analog or digital signals, or baseband or modulated signals.

One-Way vs. Two-Way Communication

• Simplex is the simplest one-way method.
• Simplex examples: radio, TV broadcasting, and beepers.
• Full duplex is two-way, enabling both parties to talk and listen simultaneously, such as a telephone.
• Half duplex is two-way, but only one party can transmit at a time, police, military, citizen band (CB) and amateur radio transmissions.

Analog Signals vs. Digital Signals

• Analog signals are smoothly and continuously varying voltage or current Examples: sine wave "tone", voice, and video (TV) signals.
• Digital signals change in steps or discrete increments
• Most digital signals use binary or two-state codes such as: telegraph (Morse code), continuous wave (CW) code, and serial binary code (used in computers).
• Many transmissions of signals originating in digital form must be converted to analog form to match the transmission medium
• Analog signals are first digitized with an analog-to-digital converter, then data could be processed by computers.

Baseband signals vs. Modulated signals

• Baseband signal refers to the information signal, whether analog or digital.
• Modulation is necessary to transmit baseband signals by radio.
• A radio-frequency (RF) wave, or radio wave, is an electromagnetic signal
• Modulation has a baseband voice, video, or digital signal which modifies another, high-frequency signal called the carrier.

Modulation and Multiplexing

• Baseband information can be sent directly and unmodified, or could be used to modulate a carrier for transmission.
• The voice is placed on wires and transmitted.
• Digital signals are applied to coaxial or twisted-pair cables for transmission in some computer networks.
• Broadband transmission occurs when a carrier signal is modulated, amplified, and sent to the antenna.
• Two common methods of modulation: Amplitude Modulation (AM) and Frequency Modulation (FM).
• Phase modulation (PM) varies the phase angle of the sine wave.
• Multiplexing allows two or more signals to share the same medium or channel.
• Three basic types of multiplexing exist: frequency division, time division, and code division.
• Modulation is an electronic technique to transmit information efficiently.
• Multiplexing lets more than one signal be transmitted concurrently over a single medium.
• Modulation makes the information signal more compatible with the medium

Electromagnetic Spectrum

• Frequency is the number of cycles of electrical signal in a given time period
• Wavelength is the distance which the signal travels during one cycle.
• Radio waves, light, X-rays, and gamma rays are all electromagnetic signals
• The electromagnetic spectrum contains all possible frequencies
• Measured in Hertz (Hz)
• Electromagnetic waves transport energy through empty space, stored in the propagating electric and magnetic fields
• Optical spectrum - exists directly above the millimeter wave region
• Three types of light waves - Infrared, Visible Spectrum and Ultraviolet

Frequency Ranges

• The electromagnetic spectrum is divided into segments:
  • Extremely Low Frequencies (ELF): 30–300 Hz
  • Voice Frequencies (VF): 300Hz–3kHz
  • Very Low Frequencies (VLF): 3–30kHz
  • Low Frequencies (LF): 30–300 kHz
  • Medium Frequencies (MF): 300kHz–3MHz; AM radio: 535–1605 kHz
  • High Frequencies (HF): 3–30 MHz
  • short waves; IBB (former VOA), BBC broadcasts; government and military two-way communication; amateur radio, CB
  • Very High Frequencies (VHF): 30–300 MHz
  • FM radio broadcasting (88–108 MHz), television channels 2–13
  • Ultra High Frequencies (UHF): 300MHz–3GHz
  • TV channels 14–67, cellular phones, military communication
  • Microwaves and Super High Frequencies (SHF): 3–30 GHz
  • Satellite communication, radar, wireless LANs, microwave ovens
  • Extremely High Frequencies (EHF): 30–300 GHz
  • Satellite communication, computer data, radar
• Optical spectrum - Ultraviolet radiation is not used for communication, but is commonly used in medicine
• Optical spectrum - Infrared radiation is produced by equipment that generates heat, commonly used for; astronomy, weapons systems, tv remotes all fiber-optic communication
• Optical spectrum - Visible Light waves' high frequency enables them to handle a tremendous amount of information and Red is low-frequency or long-wavelength light while Violet is high-frequency or short-wavelength light

Bandwidth

• Bandwidth (BW) is a portion of the electromagnetic spectrum or the range of frequencies containing information
• It is the difference between the upper and lower frequencies
• Channel bandwidth is the range of needed frequencies to transmit information
• The electromagnetic spectrum being a limited resource
• There is competition for frequencies among companies, individuals, and governments, which makes the electromagnetic spectrum a precious natural resource.
• Spectrum management is controlled by agencies like the FCC and NTIA to manage spectrum use.
• Standards are specifications and guidelines to ensure compatibility between transmitting and receiving equipment.