# what is the bandwidth of a digital channel

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#### praveen_akshay

##### Newbie level 4 as square pulses are used , is it infinity ?

#### changfa Square pulse has infinite bandwidth. You need to implement some filter on top of it. (this will introduce distortion on your square pulse)

#### sameerbabu

##### Member level 3 like raised cosine filter etc for avoiding ISI b/w symbols which arise due
to spread in time because of finite BW

##### Junior Member level 3 the bw of square pulse is =1/T where T is the high time of pulse (if base band)
if pass band signal multiply by 2
if raised cosine is used bw = Rb/2*(1+α) where α is the roll off factor of filter
sure 1/T = Rb
& second case is geneal case
if ideal nyquist channel is assumed therefore bw =Rb/2

#### salman.telecom

##### Newbie level 3 even in digital system, you don't transmit the 0's & 1's. You do modulation there as well. PCM is mostly used.

#### rednewguy

##### Full Member level 2 yes, the bandwidth of a square pulse is infinity.
but there is no practical base band digital communication to transmit square pulse. it is always passband. normally we use a raised cosine which is like a sinc with few side bands, in the time domain.

##### Junior Member level 3 ok i know that bandwidth of pulse os infinity...let me convince u by what im saying..lets draw the pulse in the frequency domain..let the pulse width in time is T therfore the pulse in frequency is equal to sinc with first null equal to 1/T &extends to infinity..& since most of power exists in the main lobe( fisrt null to null) therefore we can assume that the bandwidth of the pulse is equal to 1/T ..u can review haykin for this..&by the way im a student in faculty of engineering &we took this method this year,,...i didn't invent it..
good luck

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