Introduction to Electronic Communication

Significance of Human Communication

  • Definition of Communication: Communication is the process of exchanging information.

  • Barriers to Communication: The primary barriers to effective communication are language and distance.

  • Contemporary Societal Focus: In today's society, there is a heavy emphasis on the accumulation, packaging, and exchange of information.

  • Evolutionary Methods of Communication:

    • Face to Face: Direct personal interaction.
    • Signals: Basic non-verbal indicators.
    • Written Word: Historically involving letters and physical correspondence.
    • Electrical Innovations: Notable milestones include the Telegraph, Telephone, Radio, Television, and the Internet (Computer-based communication).

Communication Systems

  • Basic Components: Every communication system consists of three fundamental parts:

    • Transmitter: Converts the information into a signal suitable for transmission.
    • Channel or Medium: The path through which the signal travels.
    • Receiver: Extracts the information from the medium and converts it back to a human-understandables form.

  • Transmitter (TX):

    • It is a collection of electronic components and circuits designed to convert an electrical signal into a specific signal suitable for a given medium.
    • Internal Circuitry: Transmitters are composed of oscillators, amplifiers, tuned circuits and filters, modulators, frequency mixers, frequency synthesizers, and other specialized circuits.

  • Communication Channel (Medium):

    • The medium serves as the bridge between the transmitter and the receiver.
    • Types of Media:
    • Electrical Conductors: Wires and cables.
    • Optical Media: Fiber-optic cables.
    • Free Space: Used for radio wave transmission.
    • System-Specific Media: Materials like water, which serves as the medium for sonar applications.

  • Receiver (RX):

    • A collection of electronic components and circuits that accept the transmitted message from the channel.
    • Functionality: It converts the received signal back into a form understandable by humans.
    • Internal Circuitry: Receivers contain amplifiers, oscillators, mixers, tuned circuits, and filters. They specifically feature a demodulator (or detector) which recovers the original intelligence signal from the modulated carrier wave.

  • Transceiver:

    • An electronic unit that integrates both transmitter and receiver circuits in a single unit.
    • Examples: Telephones, Face machines, Handheld Citizens Band (CB) radios, Cellular phones, and Computer modems.

  • Noise:

    • Noise is random, undesirable electronic energy that enters the communication system via the medium.
    • Effect: It interferes with the transmitted message and degrades the quality of the information.

  • Attenuation:

    • Attenuation represents the degradation or loss of signal strength as it travels. It is present in all wireless transmission media.
    • Mathematical Relationship: Attenuation is proportional to the square of the distance between the transmitter and the receiver.
    • Formula Concept: Attenuation×d2\text{Attenuation} \times d^2

Types of Electronic Communication

  • Classification by Directionality:

    • Simplex (One-way): The simplest form of communication where transmission occurs only in one direction. Examples include Radio broadcasting, TV broadcasting, and Beeper (personal receiver) units.
    • Two-Way Transmissions (Duplex): Most electronic communication fits into this category.
    • Full Duplex: Occurs when both parties can talk and listen simultaneously. A standard telephone conversation is the primary example.
    • Half Duplex: Two-way communication where only one party can transmit at a time. Examples include Police and military radio, Citizens Band (CB), Family radio, and Amateur radio.

  • Classification by Signal Type:

    • Analog Signals: A signal characterized by a smoothly and continuously varying voltage or current. Primary examples are sine waves, human voice, and traditional Video (TV) signals (light variation along scan lines).
    • Digital Signals: Signals that change in discrete steps or increments. Most digital signals utilize binary or two-state codes.
    • Examples: Telegraph (Morse code), Continuous Wave (CW) code, and Serial binary code used in computers.
    • Binary States: Represented as "Mark" (on/high) and "Space" (off/low). For instance, the letter "R" in Morse code consists of Dot-Dash-Dot sequences.

  • Signal Conversion:

    • Many digital signals originate in digital form but must be converted to analog to be compatible with certain transmission media (e.g., sending digital data over telephone networks).
    • Analog signals can be digitized using an Analog-to-Digital (A/D) converter to allow for processing by computers.

Modulation and Multiplexing

  • Core Definitions:

    • Modulation: The process of making an information signal more compatible with a specific medium.
    • Multiplexing: A technique that allows more than one signal to be transmitted concurrently over a single medium or channel.

  • Baseband Transmission:

    • Refers to information sent directly and unmodified over a medium.
    • In telephone or intercom systems, voice is placed directly on the wires.
    • In some computer networks, digital signals are applied directly to coaxial or twisted-pair cables.

  • Broadband Transmission (Carrier-Based):

    • Carrier: A high-frequency signal that is modulated by audio, video, or data signals.
    • Radio-Frequency (RF) Wave: An electromagnetic signal capable of traveling long distances through space.
    • Process: A carrier signal is modulated, amplified, and sent to an antenna for transmission.

  • Methods of Modulation:

    • Amplitude Modulation (AM): Varying the amplitude of the carrier.
    • Frequency Modulation (FM): Varying the frequency of the carrier.
    • Phase Modulation (PM): Varying the phase angle of the sine wave.
    • Frequency-Shift Keying (FSK): A digital technique where data is converted into frequency-varying tones.

  • Modems (Modulator-Demodulator): Devices that translate data from digital to analog (at the source) and back again (at the destination).

  • Demodulation (Detection): The process performed in the receiver to extract the original baseband (intelligence) signal from the carrier.

  • Types of Multiplexing:

    • Frequency Division Multiplexing
    • Time Division Multiplexing
    • Code Division Multiplexing

The Electromagnetic Spectrum

  • Definition: The electromagnetic spectrum is the entire range of electromagnetic signals encompassing all possible frequencies.

  • Frequency (ff):

    • The number of cycles of a repetitive wave occurring in a given period.
    • A cycle consists of two voltage polarity reversals, two current reversals, or two electromagnetic field oscillations.
    • Measured in cycles per second (cps), with the primary unit being the Hertz (Hz).

  • Wavelength (λ\lambda):

    • The distance occupied by one cycle of a wave, or the distance an electromagnetic wave travels during one cycle.
    • Wavelength is usually expressed in meters.
    • Mathematical Relationship:     λ=vf\lambda = \frac{v}{f}     Where vv is the speed of light: 3×108 m/s3 \times 10^8\,m/s.
    • Calculation Example: For a frequency of 4 MHz4\,MHz:     λ=3×1084×106=75 meters\lambda = \frac{3 \times 10^8}{4 \times 10^6} = 75\,meters

  • Spectrum Segments:

    • Extremely Low Frequencies (ELF): 30−300 Hz30-300\,Hz.
    • Voice Frequencies (VF): 300−3000 Hz300-3000\,Hz.
    • Very Low Frequencies (VLF): Includes the higher end of human hearing up to about 20 kHz20\,kHz.
    • Low Frequencies (LF): 30−300 kHz30-300\,kHz.
    • Medium Frequencies (MF): 300−3000 kHz300-3000\,kHz. This includes the AM radio broadcast band (535−1605 kHz535-1605\,kHz).
    • High Frequencies (HF): 3−30 MHz3-30\,MHz. Used for short waves, VOA, BBC, military two-way comms, amateur radio, and CB.
    • Very High Frequencies (VHF): 30−300 MHz30-300\,MHz. Used for FM radio (88−108 MHz88-108\,MHz) and TV channels 2-13.
    • Ultra High Frequencies (UHF): 300−3000 MHz300-3000\,MHz. Used for TV channels 14-67, cellular phones, and military communication.
    • Microwaves / Super High Frequencies (SHF): 1−30 GHz1-30\,GHz. Used for satellite communication, radar, wireless LANs, and microwave ovens.
    • Extremely High Frequencies (EHF): 30−300 GHz30-300\,GHz. Used for high-capacity satellite communication, computer data, and radar.

  • The Optical Spectrum:

    • Located above the millimeter wave (EHF) region.
    • Infrared: Produced by heat-generating equipment or bodies. Applications include astronomy (detecting stars), weapons guidance (targeting heat signatures), TV remotes, fiber-optics, and wireless LANs.
    • Visible Spectrum: Referred to as light.
    • Red: Low-frequency / long-wavelength.
    • Violet: High-frequency / short-wavelength.
    • High frequencies of light allow for high bandwidth (tremendous information capacity).
    • Ultraviolet: Not used for communication; primarily used in medical applications.

Bandwidth and Spectrum Management

  • Bandwidth (BW):

    • The portion of the electromagnetic spectrum occupied by a signal.
    • Channel Bandwidth: The specific range of frequencies required to transmit a desired piece of information.

  • Spectrum Limitations:

    • Most of the spectrum between 30 kHz30\,kHz and 300 MHz300\,MHz is already fully allocated.
    • This scarcity leads to intense competition between individuals, companies, and governments.
    • The electromagnetic spectrum is considered a finite and precious natural resource.

  • Engineering Goals: Improving communication techniques to minimize required bandwidth while maximizing the number of available channels.

  • Management Agencies:

    • Federal Communications Commission (FCC): United States regulatory body.
    • National Telecommunications and Information Administration (NTIA): Sets government policy for spectrum use.
    • Standards: Specifications used to ensure technical compatibility between different transmitters and receivers.

Survey of Communication Applications

  • Simplex Applications: AM/FM broadcasting, Digital radio, TV/DTV broadcasting, Cable TV, Facsimile, Wireless remote control, Paging, Navigation/Direction-finding, Telemetry, Radio astronomy, Surveillance, Music services, Internet radio/video.

  • Duplex Applications: Telephones, Two-way radio, Radar, Sonar, Amateur radio, Citizens radio, Family Radio service, The Internet, Wide-area networks (WANs), Metropolitan-area networks (MANs), Local area networks (LANs).

Careers in the Communication Industry

  • Industry Specializations: The electronics industry is divided as follows:

    1. Communications: Largest sector by employment and dollar value.
    2. Computers: Second largest.
    3. Industrial Controls.
    4. Instrumentation.

  • Common Job Roles:

    • Engineers: Design equipment and systems.
    • Technicians: Install, troubleshoot, repair, calibrate, and maintain systems.
    • Engineering Technicians: Support design, testing, and assembly.
    • Technical Sales Representatives: Write proposals, determine customer needs, and sell equipment.
    • Technical Writers: Create documentation and technical manuals.
    • Trainers: Develop educational programs and conduct classroom instruction.

  • Industry Structure: The ecosystem consists of Manufacturers (providing components and materials), Resellers, Service Organizations, and End Users.