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Design >> Analog Design >> average noise power
https://designers-guide.org/forum/YaBB.pl?num=1324665484

Message started by singh on Dec 23^rd, 2011, 10:38am

Title: average noise power
Post by singh on Dec 23^rd, 2011, 10:38am

i have a transfer function which is multiplied with noise voltage density transfer function (flicker+white noise curve) and i get resulting data from that.

So in order to calculate avergae noise power, do i need to take Root mean square of all the values or root sum square of all the values?

Please help me on this

Title: Re: average noise power
Post by raja.cedt on Dec 23^rd, 2011, 11:34am

hello,
finally you have to find rms value of the output. but already you have output psd, so just find sum and take square root.

thanks,
raj.

Title: Re: average noise power
Post by singh on Dec 23^rd, 2011, 12:48pm

raja.cedt wrote on Dec 23^rd, 2011, 11:34am:

hello,
finally you have to find rms value of the output. but already you have output psd, so just find sum and take square root.

thanks,
raj.

thanks

for noise voltage density i use
eVN2 = eFN2/freq + eWN2;
eVN = sqrt(eVN2)

suppose my transfer function
save_tf_values(j) = variable1;
save_output_noise(j) = variable1 * eVN;

these eVN values i multiply with my transfer function for each frequency and get data.. eVN is not squared.. so i think i need i need to take rms as shown below?
rms = sqrt(mean(save_output_noise.^2))

please suggest whether this correct?

Title: Re: average noise power
Post by raja.cedt on Dec 23^rd, 2011, 2:14pm

yes, sounds correct. But why u r doing this.

Title: Re: average noise power
Post by singh on Dec 26^th, 2011, 1:04pm

i have two different transfer functions and i want to see which one has more noise power..

thanx for ur suggestions

Title: Re: average noise power
Post by aaron_do on Dec 26^th, 2011, 5:23pm

Hi,

not sure if I'm missing something here, but why did you divide EFN2 by freq?

thanks,
Aaron

Title: Re: average noise power
Post by singh on Dec 27^th, 2011, 2:33am

aaron_do wrote on Dec 26^th, 2011, 5:23pm:

Hi,

not sure if I'm missing something here, but why did you divide EFN2 by freq?

thanks,
Aaron

efn is flicker noise voltage at 1Hz and the flicker noise gives 1/freq behaviour ... i just took general formula to calculate total noise due to flicker and white noise

Title: Re: average noise power
Post by thechopper on Dec 30^th, 2011, 4:10am

If intereseted in average noise power, you need to integrate the resulting noise psd at the output.

Best
Tosei