Power of noise after passing through a system h(t)

iVenky
Messages
212
Reaction score
12
**Reposting this again, as I was asked to post this on a homework forum**
1. Homework Statement

Hi,

I am trying to solve this math equation (that I found on a paper) on finding the variance of a noise after passing through an LTI system whose impulse response is h(t)
X(t) is the input noise of the system and Y(t) is the output noise after system h(t)
if let's say variance of noise Y(t) is
σy2=∫∫Rxx(u,v)h(u)h(v)dudv

where integration limits are from -∞ to +∞. Rxx is the autocorrelation function of noise X. Can you show that if Rxx (τ)=σx2 δ(τ) (models a white noise), then

σy2=σx2∫h2(u)du (integration limits are from -∞ to +∞)

and if Rxx (τ)=σx2 (models a 1/f noise), then

σy2=σx2(∫h(u)du)2 (integration limits are from -∞ to +∞)

I don't understand the math behind statistics that well
Thanks

Homework Equations


Can I write σy2=∫∫Rxx(u,v)h(u)h(v)dudv as
σy2=∫∫Rxx(τ)h(u)h(u+τ)dudτ
if noise X(t) is stationary process?
However, I am not sure how Rxx (τ)=σx2 δ(τ) or σx2 results in those different equations shown above

The Attempt at a Solution



Same as before
 
Physics news on Phys.org
Hi,
Can you tell me if there is a better forum for this question to get an answer?
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

Similar threads

Back
Top