# 1. why a gaussain noise is added to the channel output in eye diagram??

Discussion in 'General Electronics Chat' started by bandpass, Apr 19, 2011.

1. ### bandpass Thread Starter New Member

Apr 19, 2011
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I use raised cosine function of Matlab to act as the impulse response of a bandlimited channel. The received waveform has transient responses at the beginning and at the end.

how could I remove the transient response of the received waveform before the generation of eye-diagram? will there be any inter-symbol interference (ISI) at the optimum sampling point? How to reduce/eliminate it?

2. ### bandpass Thread Starter New Member

Apr 19, 2011
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0
gaussain noise is what every engineer from time to time tries to get rid of in telecommunication. isnt it???

in my recent experiment on eye diagram simulation, it was somehow added into, what is the <snip> purpose??

and if the original cutoff frequency = 1, the sampling frequency=20 and samples per symbol =10, length of the response=200, roll-off factor =0.15,
now I want to change roll-off factor and length of the response into following figures, what are the changes on eye-diagram ?

(a) roll-off factor = 0.1, length of the response (N) = 60 & 200
(b) roll-off factor = 0.9, length of the response (N) = 60 & 200

i was told that there is basically no change in eye-diagram for N=60 & 200 in (b), but dont get it, do u all have an idea???

Last edited by a moderator: Apr 19, 2011
3. ### Ron H AAC Fanatic!

Apr 14, 2005
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I doubt that I can help you, but if you expect anyone to be able to help, you will need to tell us the name of the simulator.

4. ### bandpass Thread Starter New Member

Apr 19, 2011
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what do u mean by the simulator? in my experiemt, the raised cosine function of Matlab [‘firrcos(N, Fc, , Fs, ‘rolloff’)’] was used to act as the impulse response of a bandlimited channel.

uploaded is the whole procedure, plz have a look, thx

5. ### beenthere Retired Moderator

Apr 20, 2004
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Note: These threads share a common topic, so they have been merged. Post #1 was a separate thread.