i am confused about N0 and N0/2

[ddt694]

n0/2 noise

in field of communication or PLL, single side noise power spectral density No and double side No/2 are used widely, what is the difference between them?

thanks!

 

[cmunikat]

noise power n0/2

ddt694

Generally, those symbols are used for measuring white noise power spectral density (ped). Both things are the same, however, you should be careful when using them: They are used to describe noise characteristics in different contexts.

When all signals and systems are considered for frequencies between + to - inf, you should use N0/2 [W/Hz].

In contrast, when signals and systems are considered for f>0, use N0 [W/Hz].

For example, if ideal white noise is applied to an ideal unitary gain band pass filter of B Hz bandwidth, the noise power at its output is N0xB. To get this result you can do the following:

For freq +/- inf:

Power = power for f<0 + power for f>0
= ped f<0 x BW f<0 + ped f>0 x BW f>0
= N0/2xB + N0/2xB
= N0xB

For freq >0:

Power = power for f<0 +power for f>0
= 0 + ped f>0 x BW f>0
= N0xB


Cmunikat

 

[biff44]

white noise n0/2

3 dB