EE100CH12 - Communication Systems Definition of...

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Unformatted text preview: Communication Systems Definition of Communication System Parts of a Communication System Source Transmitter Analog and Digital Channel Wired and Wireless Allocation Receiver Computer Networks OSI Model Network Devices Topologies System Classification Encoding Introduction Communication is the process of exchanging information , and the technology of transmitting information . (From Wikipedia) A Communication System facilitates the movement of information from one place to another. There are five basic parts associated with a typical communication systems Part 1. The Source The source generates the signal that we wish to communicate. Signal sources can be analog or digital Examples Audio Signals Video Signals Computer Data Part 2. The Transmitter The transmitter bridges the source and transmission media , source signals must be converted into a form that can be transmitted over some specific physical medium Designer must know, Information analog or digital Transmission channel wireless or cable Type of signal modulation needed Transmitter details (designs) are based on, Information type Channel type Modulation type Modulation: Modulation is a operation that uses the source information to modify a signal so that it is more suited for transmission over a given channel. Modulation basically works like this: The message that we want to transmit (the modulating signal) interacts with, or modulates a higher frequency signal (the carrier wave) by inducing a change in some particular aspect of the carrier wave, for example its amplitude, frequency, or phase . The resulting waveform is a high frequency signal that has the lower frequency message signal embedded in it. Purpose of Modulation: 1. To achieve most effective use of the available channel On any given channel that is shared by several entities, there is a need for each of these entities to use the channel without causing problems for the others. Without modulation, only one radio station could broadcast information at a time. 2. Reduction of antenna length for wireless systems Antenna length is proportional to transmission wavelength, which is inversely proportional to frequency, so if we modulate our signal at higher frequencies, meaning shorter wavelengths, results in shorter antenna lengths f c = 4 = h Calculate the antenna lengths required for the following signal frequencies meters 000 , 30 000 , 10 10 3 8 = = x meters 3 . 10 1 10 3 9 8 = = x x 10,000 Hz 1 GHz Miles 4.66 meters 500 , 7 4 000 , 30 = = h Inches 2.95 or cm 7.5 meters 075 . 4 3 . = = = h Equations: Quarter wavelength antenna Click Me Modulation Types: there are many types, or techniques, of modulation, and simple modulation can be divided into two groups, analog and digital....
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This note was uploaded on 12/14/2011 for the course EE 1001 taught by Professor Hite during the Fall '11 term at University of Alabama - Huntsville.

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EE100CH12 - Communication Systems Definition of...

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