Phase noise generation

Hi,
  I am trying to add phase noise to a QAM signal. Can anyone tell me how
to generate phase noise in matlab.Any help will be greatly appreciated.


		
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I think you will have to use complex signals, i.e., I/Q channels.  Then with 
noise in both channels, you have phase noises.  Most of time, we assume the 
two channels have the same iid Gaussian noise and in that case, your phase 
noise is uniformly distributed between 0 and 2pi while your noise amplitude 
is Rayleigh distributed.


"pchennu" <chennu_pushkar@yahoo.com> wrote in message 
news:RredndSKJMvOzWrfRVn-tQ@giganews.com...
> Hi,
>  I am trying to add phase noise to a QAM signal. Can anyone tell me how
> to generate phase noise in matlab.Any help will be greatly appreciated.
>
>
>
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com 

"pchennu" <chennu_pushkar@yahoo.com> wrote in message 
news:RredndSKJMvOzWrfRVn-tQ@giganews.com...
> Hi,
>  I am trying to add phase noise to a QAM signal. Can anyone tell me how
> to generate phase noise in matlab.Any help will be greatly appreciated.

c(t)=sin(wt + phi) ????

Phi would be a random number uniformly distributed between 0 and 2pi.
You have to decide how fast phi can change from sample to sample.  That's a 
system parameter.
So, if you generate phi for every sample of c(t) then probably you need to 
lowpass filter phi before adding it to wt - and then scale the result up to 
accomodate the affect of the filter (you have removed energy from the phase 
noise signal that needs to get back).  The bandwidth of the filter is up to 
you.

Then you treat this basic building block as you'd treat any sinusoid in your 
model.

Fred 

Fred Marshall wrote:
> "pchennu" <chennu_pushkar@yahoo.com> wrote in message 
> news:RredndSKJMvOzWrfRVn-tQ@giganews.com...
> 
>>Hi,
>> I am trying to add phase noise to a QAM signal. Can anyone tell me how
>>to generate phase noise in matlab.Any help will be greatly appreciated.
> 
> 
> c(t)=sin(wt + phi) ????
> 
> Phi would be a random number uniformly distributed between 0 and 2pi.
> You have to decide how fast phi can change from sample to sample.  That's a 
> system parameter.
> So, if you generate phi for every sample of c(t) then probably you need to 
> lowpass filter phi before adding it to wt - and then scale the result up to 
> accomodate the affect of the filter (you have removed energy from the phase 
> noise signal that needs to get back).  The bandwidth of the filter is up to 
> you.
> 
> Then you treat this basic building block as you'd treat any sinusoid in your 
> model.
> 
> Fred 
> 
> 
You could also use a Von Mises distribution, the uniform on -pi to pi is 
a special case.  Unfortunately the only Von Misses RNGs that I know of, 
are kind of slow.

Try doing a "Phase noise" search in this newsgroup. There are a few threads 
that may be useful to you.

"pchennu" <chennu_pushkar@yahoo.com> wrote in message 
news:RredndSKJMvOzWrfRVn-tQ@giganews.com...
> Hi,
>  I am trying to add phase noise to a QAM signal. Can anyone tell me how
> to generate phase noise in matlab.Any help will be greatly appreciated.
>
>
>
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com