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Related Content: CS601  VU Lectures, Handouts, PPT Slides, Assignments, Quizzes, Papers & Books of Data Communication
Frequency Spectrum / Bandwidth
 Frequency Spectrum: of a signal is the collection of all the component frequencies it contains
 It is shown using a Frequency domain graph
 Bandwidth: of a signal is the width of the frequency spectrum
 In other words ,Bandwidth refers to the range of the component frequencies and Frequency Spectrum refers to the elements within that range
How to calculate Bandwidth?
 To calculate Bandwidth, subtract the lowest frequency from the highest frequency
Example 4.8
If a periodic signal is decomposed into five sine waves with frequencies 100, 300, 500, 700, and 900 Hz, what is the Bandwidth?
Solution
Other Definitions of Bandwidth

3 dB Bandwidth or Half Power Bandwidth
H( f )

Equivalent Noise Bandwidth
The width of a fictitious rectangular spectrum created to have the same power in the rectangular band as the power of the signal in positive frequencies

NulltoNull Bandwidth or Zero Crossing Bandwidth
Frequency Band in which 99% of the total power resides
In addition to being represented by Analog Signals, data can also be represented by a Digital signal

Bit Interval and Bit Rate
Most digital signals are aperiodic and thus Period and Frequency are not the appropriate terms to describe them
 Bit Interval (seconds)
 Time required to send one single bit
 Bit Rate (bps)
 Number of bits sent per second
Frequency Spectrum of a Digital Signal
 Frequency spectrum of a digital signal contains an infinite number of frequencies with different amplitudes
 Ideally we want to send all the components but if we send only those components whose amplitudes are significant , we can still recreate the digital signal with reasonable accuracy at the receiver
Summary
 Frequency Spectrum and Bandwidth
 Other Definitions of Bandwidth
 Digital Signals
Reading Sections
 Section 4.4, 4.5, 4.6 “Data Communications and Networking” 4th Edition by Behrouz A. Forouzan