Bandwidth_Chapter16

Bandwidth_Chapter16 - SIMS201 WhatisBandwidthand...

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SIMS-201 What is Bandwidth and How it is Used
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2 Overview Chapter 16 (continued) Bandwidth Shannon’s theorem Communication systems Analog Modulation AM FM Digital Modulation ASK FSK Modems
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3 Bandwidth In previous lectures, we briefly mentioned the concept of  bandwidth. In this lecture, we will discuss more deeply what  signal bandwidth  is, what the meaning of  channel bandwidth  to  a communications engineer is, and what the limitations on  information rate are. Signal bandwidth: We can divide signals into two categories: The  pure tone  signal (the  sinusoidal wave, consisting of one frequency component), and  complex   signals that are composed of several components, or sinusoids of various  frequencies.   t (ms) T=1x10 -3 s f=1/1x10 -3 =1000Hz=1 kHz 0 1 Pure signal
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4 The  bandwidth  of a signal composed of components of various frequencies (complex  signal) is the  difference between its highest and lowest frequency components , and is  expressed in Hertz (Hz) - the same as frequency. For example, a square wave may be constructed by adding sine waves of various  frequencies:  The resulting wave resembles a square wave. If more sine waves of other frequencies  were added, the resulting waveform would more closely resemble a square wave Since the resulting wave contains 2 frequency components, its bandwidth is around  450-150=300 Hz. (ms) 150 Hz sine wave 450 Hz sine wave Approaching a 150 Hz square wave Pure tone Pure tone
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5 Since voice signals are also  composed of several  components (pure tones) of  various frequencies, the  bandwidth of a voice signal is  taken to be the difference  between the highest and lowest  frequencies which are 3000 Hz  and (close to) 0 Hz Although other frequency  components above 3000 Hz  exist, (they are more prominent  in the male voice), an  acceptable degradation of voice  quality is achieved by  disregarding the higher  frequency components,  accepting the 3kHz bandwidth  as a standard for voice  communications  Male voice Female voice 3000 Hz frequency component 3000 Hz frequency component
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6 channel bandwidth:  The bandwidth of a channel (medium) is defined to be the range of  frequencies that the medium can support. Bandwidth is measured  in Hz  With each transmission medium, there is a frequency range of  electromagnetic waves that can be transmitted: Twisted pair cable: 0 to 10 9  Hz   (Bandwidth : 10 Hz) Coax cable: 0 to 10 10  Hz  (Bandwidth : 10 10  Hz) Optical fiber: 10 14  to 10 16  Hz  (Bandwidth : 10 16  -10 14  = 9.9x10 15  Hz) Optical fibers have the highest bandwidth (they can support 
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This note was uploaded on 01/20/2012 for the course EE 301 taught by Professor Ahmetçakar during the Spring '11 term at Gazi Üniversitesi.

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Bandwidth_Chapter16 - SIMS201 WhatisBandwidthand...

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