Page 48 - DCAP311_DCAP607_WIRELESS_NETWORKS

Wireless Networks

Notes signals. RF usually refers to electrical rather than mechanical oscillations; however, mechanical
RF systems do exist.
Although radio frequency is a rate of oscillation, the term “radio frequency” or its abbreviation
“RF” are also used as a synonym for radio – i.e. to describe the use of wireless communication, as
opposed to communication via electric wires.

Example: Radio-frequency identification and ISO/IEC 14443-2 Radio frequency power
and signal interface.

To receive radio signals an antenna must be used. However, since the antenna will pick up
thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency
(or frequency range). This is typically done via a resonator – in its simplest form, a circuit with
a capacitor and an inductor forming a tuned circuit. The resonator amplifies oscillations within
a particular frequency band, while reducing oscillations at other frequencies outside the band.
Fiber-optic communication is a method of transmitting information from one place to another by
sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave
that is modulated to carry information. First developed in the 1970s, fiber-optic communication
systems have revolutionized the telecommunications industry and have played a major role in
the advent of the Information Age. Because of its advantages over electrical transmission, optical
fibers have largely replaced copper wire communications in core networks in the developed
world.
The process of communicating using fiber-optics involves the following basic steps: Creating the
optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that
the signal does not become too distorted or weak, receiving the optical signal, and converting it
into an electrical signal.
Fiber optics is a medium for carrying information from one point to another in the form of light.
Unlike the copper form of transmission, fiber optics is not electrical in nature. A basic fiber optic
system consists of a transmitting device that converts an electrical signal into a light signal, an
optical fiber cable that carries the light, and a receiver that accepts the light signal and converts it
back into an electrical signal. The complexity of a fiber optic system can range from very simple
(i.e., local area network) to extremely sophisticated and expensive (i.e., longdistance telephone
or cable television trunking).

Example: The system shown in Figure below could be built very inexpensively using
a visible LED, plastic fiber, a silicon photodetector, and some simple electronic circuitry. The
overall cost could be less than $20.

On the other hand, a typical system used for long-distance, high-bandwidth telecommunication
could cost tens or even hundreds of thousands of dollars.

3.1 Wireless Transceivers

An infrared transceiver, or IR transceiver, is capable of both sending and receiving infrared data.
In other words an IR transceiver is a transmitter and a receiver housed together in one single
unit and having circuitry in common. IR transceivers are often used for portable or mobile use.
Some transceivers can do both functions at the same time, while other transceivers can only do
one function at a time. The device may either have a focused beam, thus requiring it to be in a
precise position in order to function properly, or it may be a broader beam, depending on the
applications that it is designed for.
There are many different kinds of infrared transceivers. The most common types categorized by
speed, size, supply voltage, link, data rate, packaging type and maximum idle current.

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