Time averaging problem

[mustaine]

Hi all,

I encounter a problem using time averaging function in Labview. The time averaging is utilized to improve the SNR. However, when I use the time average function, both useful signal and noise will be suppress, hence no improvement in SNR. I have no idea why this is happened.


The signal given by I= cos[Acos(2*pi*20000(t) + p(t) +n(t)],

where     n(t) is a white noise
              p(t) is a periodic signal


Any idea to overcome this is highly appreciated.  Attached is my labview file.
I have been using Labview for 2 years but very awful in signal processing.

[Ray.R]

Is it possible to save it as LV8.2 so that I can have a look at it?  It is the version that I have on this PC.

Thanks,

R

[mustaine]

Here it is.. Thank you.

[mustaine]

I suspect the problem is related to the synchronization of the information signal. Since the signal is sinusoidal, out of phase sum operation  can cause destructive interference.

However when I do averaging in frequency domain, only noise is suppressed and information signal is remained.

[Ray.R]

Thanks,

I'll have a look at it.

R

[johnsold]

mustaine,

You are right that the out of phase summation is causing the output to be suppressed.  Connect a graph to the array going into or coming from the Cosine function and you will see the phase shifting.  Increase the wait time to make it easier to see.

When you want to average signals to reduce noise, you need some kind of synchronization.  It must be tied to the desired signal phase.  How you get it depends very much on the source of the signal (and noise and interference) and what you are actually trying to do with the signal.

Lynn 

[Ray.R]

Sorry,

I've been busy & away from the forum.  Did Lynn provide a solution for you?