History of Electronic Communications

Brief History of Electronic Communications

• Modern electronics commenced with early radio communications.
• Wireless transmission for radio communications originated from Heinrich Hertz's work in 1887.
• Radio waves can travel without wires between transmitting and receiving equipment.
• Radio and light waves travel at the same velocity
• Both are examples of electromagnetic radiations, combining electricity and magnetism, transmitting electric energy through space.
• In 1895, Guglielmo Marconi demonstrated wireless telegraphy.
• By 1901, wireless communication crossed the Atlantic Ocean.
• Electronic communications grew due to the invention of the audion tube in 1906.
• The development of vacuum tubes led to rapid advancements in electronics and communications.

Timeline of Electronic Communications

• 1440: Gutenberg invented the printing press.
• 1844: Morse patented the telegraph.
• 1864: Maxwell concluded the relationship between light, electricity, and magnetism.
• 1866: The first successful transatlantic cable was used.
• 1876: Bell invented and patented the telephone.
• 1877: Edison invented the phonograph.
• 1879: Eastman developed photographic film.
• 1880: Hertz discovered electromagnetic waves.
• 1887: Hertz discovered radio waves.
• 1895: Marconi demonstrated wireless telegraphy.
• 1897: Braun invented the first CRT oscilloscope.
• 1901: Marconi made the first transatlantic radio transmission.
• 1903: The Fleming valve was invented.
• 1906: De Forest invented the triode vacuum tube.
• 1906: Fessenden demonstrated the first electronic voice communication.
• 1914: Armstrong developed the superheterodyne radio receiver.
• 1920: The first commercial AM radio broadcast occurred.
• 1923: Zworykin invented the iconoscope and television.
• 1939: The first use of two-way radio communication.
• 1940-45: RADAR was perfected.
• 1941: Commercial television broadcasting started.
• 1948: Bell Labs invented the transistor.
• 1953: Color television broadcasting began.
• 1959: Integrated circuits were invented.
• 1962: The first communication satellite was launched.
• 1969: Stereo FM broadcasting began.
• 1970: ARPA developed packet switching technology.
• 1970: HDTV was introduced in Japan.
• 1971: The microprocessor was invented.
• 1976: The VHS home recording format was introduced.
• 1977: The first commercial use of optical fiber cables.
• 1981: IBM PC was introduced and the first cellular telephone network began.
• 1983: Cellular telephone networks were introduced in the US.
• 1989: The World Wide Web debuted.
• 1990: The first digital cellular network began.
• 1993: The Pentium chip hit the market.
• 1995: The Global Positioning System was deployed.
• 1996: The first smartphone.
• 1997: The first wireless LANs.
• 1998: Bluetooth was formed by Ericsson, IBM, Intel, Nokia & Toshiba.
• 1999: HDTV standards were implemented in the US and DTV transmission began.

Elements of a Communication System

• Electronic communications involve sending, processing, and receiving data via electrical means.
• Any communication system needs both accurate and fast communication.
• Types of communication systems developed include radio, telephony, telegraphy, broadcasting, radar, radio telemetry, and radio aids to navigation.

Electronic Communication System

• The primary role is to transport info from one location to another.

Block Diagram of a Communication System

• Information flows from a source, through a transmitter where it's encoded and modulated, then through a channel which can introduce distortions and noise.
• A receiver decodes and demodulates the signal before it reaches its destination.

Electronic Communication

• The process by which information is transmitted, received, and processed between two or more locations through electronic circuits.

Information

• It is the physical manifestation of data traveling from the source to the destination.

Source

• The originator of the information.

Transmitter

• A group of electronic parts and circuits designed to convert an electrical signal into a signal suitable for transmission over a medium.

Modulation

• A process where a baseband signal modifies a higher frequency signal known as the carrier.
• Info is impressed upon a carrier, usually a sine wave generated by an oscillator.

Encoder

• Alters the signal's form, preparing it for transmission.

Communication Channel

• Electrical or electromagnetic connection that bridges the gap between source and destination.
• It uses media like wire conductors, fiber-optic cable, and free space.

Electrical Conductors

• The medium can be wire pairs for voice signals, coaxial cables for TV signals, or twisted-pair cables in LANs.
• They are also known as transmission lines or line communication, using overhead lines or buried cables, commonly in telephone and telex networks.

Optical Media

• Can be fibre-optic cables or "light pipes" carrying data on a light wave.
• Used for long-distance calls and Internet, converting info to digital to control a laser diode at high speeds.
• They are also known as light waves or fiber optics (FO) communication.
• They transmit light signals through thin fibers of glass or transparent solids.

Free Space

• Commonly known as wireless or radio, it involves wireless communication from one point to another using the electromagnetic spectrum.
• Communication via visible/infrared light also takes place.
• It uses signal propagation through the atmosphere, also known as free space propagation.
• Intelligence signals are converted to electric and magnetic fields.

Noise

• Consists of unwanted, random signals which disrupt the clarity of intended data.

Distortion

• Refers to changes in a signal that alter basic waveform.

Attenuation

• Signal attenuation or degradation, refers to losing signal in a communication system.
• Attenuation is proportional to the distance squared between receiver and transmitter.

Decoder

• Produces the signal for comprehension at the destination.

Receiver

• A collection of electronic components/circuits that accepts the transmitted message from channel and reconverts it to a human-understandable form.

Destination

• The end user of an electrical signal.

Types of Signal

• Encoders produce two kinds of electrical signals: analog and digital.

Analog Signals

• Smoothly and continuously varying voltage.
• Voice and video voltages mirror sound or light variations.

Digital Signals

• Change in steps or discrete movements unlike analog signals.
• Generally use binary or two-state codes.

Communication Channels

• Electrical Conductors
• Optical Media
• Free Space

Transmission Modes

• Simplex
• Duplex (Half Duplex, Full Duplex)

Simplex

• Communication occurs in one direction.
• Sender can only transmit, receiver can only receive; the receiver cannot reply.

Half Duplex

• Communication occurs both ways, but one way at any time.
• Both sender and receiver can send/receive, but not concurrently.

Full Duplex

• Communication occurs simultaneously.
• Sender and receiver can both send/receive at same time.

3 Components of a Transmitter

• Transmitting Antenna: Radiates electromagnetic waves.
• Modulating Amplifier: Accomplishes the modulation process.
• Oscillator: Produces the carrier wave.

3 Components of a Receiver

• Receiving Antenna: Captures the signal.
• Demodulator: Extracts the signal from carrier wave.
• Oscillator: Incorporates the inside tuning circuit.

Electromagnetic Spectrum

• Info travels via electrical signals converting and radiating into space composed of electrical/magnetic fields that go through space.
• Signals are radio frequency (RF) waves.
• Electromagnetic waves are signals that oscillate, varying electric and magnetic field intensity.
• Field intensities fluctuate given number of times per second.
• Electromagnetic waves vary sinusoidally.
• Their frequency is measured in cycles per second (cps) or Hertz (Hz).
• Oscillations occur at very low or high frequencies.
• The entire frequency range is the electromagnetic spectrum.
• c represents the speed of light at 3 x 10^8 m/s; wavelength lambda is in meters; frequency f is in Hertz.

Electromagnetic Spectrum Table

• Extremely Low Frequency: 30 – 300 Hz.
• Voice Frequency: 300 – 3000 Hz.
• Very Low Frequency: 3 – 30 kHz.
• Low Frequency: 30 – 300 kHz.
• Medium Frequency: 300 – 3000 kHz.
• High Frequency: 3 – 30 MHz.
• Very High Frequency: 30 – 300 MHz.
• Ultra High Frequency: 300 – 3000 MHz.
• Super High Frequency: 3 – 30 GHz.
• Extremely High Frequency: 30 – 300 GHz.
• Infrared Light: 300 – 3000 GHz.
• Infrared Light: 3 – 30 THz.
• Infrared Light: 30 – 300 THz.
• Visible Light: 300 – 3000 THz.
• Ultraviolet Light: 3 – 30 PHz.
• X-rays: 30 – 300 PHz.
• Gamma Rays: 300 – 3000 PHz.
• Cosmic Rays: 3 – 30 EHz.

Specific Values

• Direct Current: 0 Hz.
• Power Frequency: 10 – 1000 Hz.
• Audio Frequency: 20 – 20000 Hz.
• Voice Frequency: 300 – 3400 Hz.
• Video Frequency: 50 Hz – 4.5 MHz.
• Supersonic/Ultrasonic Frequency: 25 kHz – 2 MHz.

Applications

• Extremely Low Frequency: AC power distribution/low frequency telemetry.
• Voice Frequency: Human Conversation.
• Very Low Frequency: Upper end of hearing range/submarine communication (24kHz).
• Low Frequency: Marine and aeronautical communications/navigational beacons/LORAN navigation system (100 kHz).
• Medium Frequency: Commercial AM Radio Broadcast (535 – 1605 kHz).
• High Frequency: Short wave radio/two way communications (136 – 174 MHz)/Amateur & Citizen Band radio.
• Very High Frequency: Air Navigation (108 – 118 MHz)/Air Communication (118 – 136 MHz)/Marine & Aeronautical comm (216 – 220 MHz)/Commercial FM radio (88 – 108 MHz)/Commercial TV Broadcast (channels 2 to 13).
• Ultra High Frequency: Mobile communication service (GSM, GPS)/RADAR & Navigational systems/Microwave & Satellite radio systems/Commercial TV Broadcast (channels 14 to 69: 470 – 806 MHz).
• Super High Frequency: Microwave communications/Satellite communications and RADAR.
• Extremely High Frequency: Satellites communications/Specialized radars/Car radar (76 GHz).