Bandwidth of Transmission Medium
A transmission medium is a material substance (solid, liquid, gas, or plasma) that can propagate energy waves.
For example, the transmission medium for sounds is usually air, but solids and liquids may also act as transmission media for sound.
The absence of a material medium in vacuum may also constitute a transmission medium for electromagnetic waves such as light and radio waves.
While material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance by absorption or by reflection orrefraction at the interfaces between media.
Classification
A transmission medium can be classified as a:
Linear medium, if different waves at any particular point in the medium can be superposed;
Bounded medium, if it is finite in extent, otherwise unbounded medium;
Uniform medium or homogeneous medium, if its physical properties are unchanged at different points;
Isotropic medium, if its physical properties are the same in different directions
Types of transmissions
A transmission may be simplex, half-duplex, or full-duplex.
In simplex transmission, signals are transmitted in only one direction; one station is a transmitter and the other is the receiver.
In the half-duplex operation, both stations may transmit, but only one at a time.
In full duplex operation, both stations may transmit simultaneously.
In the latter case, the medium is carrying signals in both directions at same time.
There are two types of transmission media:Guided
Unguided
Guided Media:
Un-shielded Twisted Pair (UTP)
Shielded Twisted Pair
Coaxial Cable
Optical Fiber
Unguided Media:
Transmission media then looking at analysis of using them unguided transmission media is data signals that flow through the air.
They are not guided or bound to a channel to follow. Following are unguided media used for data communication:
Radio Transmission
Microwave
Bandwidth of different types of transmission media
| Transmission media | Frequency range (Approx.) | |
|---|---|---|
| Twisted pair | 1MHz to 100 MHz | |
| Coaxial cable | 0 to 750 MHz | |
| Fibre optics | 180 THz to 330 THz | |
| Amplitude Modulated (AM) | 450 KHz to 1600 KHz | |
| Amplitude Modulated (FM) | 88 MHz to 105 GHz | |
| Microwave | 1 GHz to 30 GHz | |
| Satellite | 1 GHz to 40 GHz |
Advantages and disadvantages of microwave transmission
Advantage are as follows:
Able to transmit large quantities of Data.
Relatively low costs.
Disadvantage are as follows:
Solid Objects.
Subject to electromagnetic and other interference.
The requirement of a line of sight limits the separation between stations to the visual horizon.
Advantage of satellite communication
The satellites provide three types of communication services as telecommunications, broadcasting, and data communications.
The satellite transmission is ideal for point-to-multipoint communications such as broadcasting. transmission, satellites can distribute signals from one point to many locations.
The Communications satellites are used for television, telephone, radio, internet, and for military applications