Chapter 16.1 ?

WIRELESS COMMUNICATION

What does Wireless Communications mean?

Wireless communications is a type of data communication that is performed and delivered

wirelessly. This is a broad term that incorporates all procedures and forms of connecting and

communicating between two or more devices using a wireless signal through wireless communication

technologies and devices.

Who performe

d this experime

nt?

In 1886 the German physicist, Heinrich Hertz (1857-1894) performed an experiment which paved the

way for another communications revolution.

TRIVIA

Examples

Radio and satellite communication are also wireless. They operate without wires between the transmitter

and the receiver. Instead, communication takes place through ELECTROMAGNETIC WAVES

WHAT IS ELECTROMAGNETIC

WAVES?

Electromagnetic waves are waves which can travel through the vacuum of outer space. Mechanical waves, unlike electromagnetic

waves, require the presence of a material medium in order to transport their energy from one location to another.

- consist of vibrating electric and magnetic fields that move through space at the speed of light.They have short wavelength-An accelerating charged particle produces an electromagnetic (EM)wave. Electromagnetic waves are electric and magnetic fields traveling through empty space with the speed of light c. A charged particle oscillating about an equilibrium position is an accelerating charged particle.

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-For the propagation and interception of radio waves, a transmitter and receiver are employed. A radio wave acts as a carrier of information-bearing signals; the information may be encoded directly on the wave by periodically interrupting its transmission

Receiving antennas intercept part of this radiation, change it back to the form of electrical signals, and feed it to a receiver. The most efficient and most common circuit for radio-frequency selection and amplification used in radioreceivers is the superheterodyne.

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The source that produce them and methods of their detection are different, but they have the following common properties :

Electromagnetic waves are propagated by oscillating electric and

magnetic fields oscillating at right angles to each other.

Electromagnetic waves travel with a constant velocity of 3 x 108 ms-1 in vacuum.

Electromagnetic waves are not deflected by electric or magnetic field.

Electromagnetic waves can show interference or diffraction.

Electromagnetic waves are transverse waves.

Electromagnetic waves may be polarized.

Electromagnetic waves need no medium of propagation. The energy from the sun is received by the earth through electromagnetic waves.

Electromagnetic radiation is used for communications and transmission of information. The waves that are used in this way are radio waves, microwaves, infrared radiation and light.

The idea of using a signal lamp to communicate was used in the 19th century. This method of long distance communication needed a code. One code used was Morse code, a series of long and short flashes of light for different letters of the alphabet. These signals can only be seen when visibility is

good and for short distances.

That’s All