# Communication Ques

Discussion in 'Radio and Communications' started by Electroenthusiast, Aug 18, 2010.

1. ### ElectroenthusiastMember

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Can anyone explain Concept of Bandwidth & its significance?
No negative frequency, but still bandwidth =2fm(amplitude modulation).
Can any one explain?

Last edited: Aug 18, 2010
2. ### RadioRonWell-Known Member

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While your question is a bit broad, here are some basic facts.

Bandwidth refers to the amount of frequency spectrum that is being used. For example, the bandwidth of a filter is the width of that filter, in Hz, where the filter attenuation increases to -3dB relative to the inband attenuation. The bandwidth of a signal is the amount of frequency spectrum occupied by the majority of the signal's power. For example, an AM modulated carrier occupies a bandwidth that depends on the frequency of modulation. If the modulation is a sine wave at, say, 2Khz, then the bandwidth of the modulated carrier (the signal) is 4Khz. The bandwidth of a modulated signal depends a great deal on the type of modulation.

When I say "by the majority of the signal's power" I refer to common ways of defining the edge of a signal's spectrum. One common way is to define the edge of a signal in the frequency domain as the point where the signal's power drops to 20 dB below the mean power.

3. ### ElectroenthusiastMember

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what's the significance of bandwidth?
why bandwidth is 2fm; while there is no negative frequency?

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5. ### ElectroenthusiastMember

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had a simple question...
why is the voltage gain in 2nd order butterwrth filter exactly 1.586?
why cant it be anyother value?