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  #1 (permalink)  
Old 06-17-2009, 02:51 AM
sauravrt
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Default white noise power

Matlab command y1 = wgn(100,1,10) generates a column vector of length 10
containing real white Gaussian noise of power 10 dBW.
How can I verify that the power of the 100 samples is 10 dBW ?




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  #2 (permalink)  
Old 06-17-2009, 12:48 PM
julius
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Default Re: white noise power

On Jun 16, 8:51*pm, "sauravrt" <sauravtulad...@hotmail.com> wrote:
> Matlab command *y1 = wgn(100,1,10) *generates a column vector of length 100
> containing real white Gaussian noise of power 10 dBW. *
> How can I verify that the power of the 100 samples is 10 dBW ?


You generated a bunch of numbers. I suppose that you can pretend that
they represent values of amplitude. Now you are asking about dBW,
which is a unit of power. You should review what is the relationship
between amplitude such as voltage, and power. Further, you are
working in discrete time. You should also review the representation
of signals in discrete time.

Julius
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  #3 (permalink)  
Old 06-17-2009, 03:01 PM
cpshah99
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Default Re: white noise power

>Matlab command y1 = wgn(100,1,10) generates a column vector of lengt
100
>containing real white Gaussian noise of power 10 dBW.
>How can I verify that the power of the 100 samples is 10 dBW ?
>


Try 10*log10(var(y1)) and see what u get.

Chintan
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  #4 (permalink)  
Old 06-19-2009, 03:53 AM
sauravrt
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Default Re: white noise power

@Julius: Thanks for the reminder. I know that

P_y = (1/N)*sum(y.*y)
That would give me the time average power of the bunch of numbers (fro
wgn).

I'm want to get an analytic expression for P_y for N samples of WGN.
Suggest me with that.
Thanks


>On Jun 16, 8:51=A0pm, "sauravrt" <sauravtulad...@hotmail.com> wrote:
>> Matlab command =A0y1 =3D wgn(100,1,10) =A0generates a column vector o

le=
>ngth 100
>> containing real white Gaussian noise of power 10 dBW. =A0
>> How can I verify that the power of the 100 samples is 10 dBW ?

>
>You generated a bunch of numbers. I suppose that you can pretend that
>they represent values of amplitude. Now you are asking about dBW,
>which is a unit of power. You should review what is the relationship
>between amplitude such as voltage, and power. Further, you are
>working in discrete time. You should also review the representation
>of signals in discrete time.
>
>Julius
>

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  #5 (permalink)  
Old 06-19-2009, 04:26 AM
Tim Wescott
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Default Re: white noise power

On Tue, 16 Jun 2009 19:51:56 -0500, sauravrt wrote:

> Matlab command y1 = wgn(100,1,10) generates a column vector of length
> 100 containing real white Gaussian noise of power 10 dBW. How can I
> verify that the power of the 100 samples is 10 dBW ?


dBW? You mean "Decibels -- Watts"?

If so, put the vector of numbers in a calorimeter for one second, and see
if it registers one Joule of heat energy.

--
www.wescottdesign.com
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  #6 (permalink)  
Old 06-21-2009, 03:41 AM
sauravrt
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Default Re: white noise power

Tim:

Since I dont' have a calorimeter at my disposal at this point of time,
just decided to digg thru Matlab help on wgn and this is what they have t
say:

y = wgn(m,n,p) generates an m-by-n matrix of white Gaussian noise.
specifies the power of y in decibels relative to a watt. The default loa
impedance is 1 ohm.

Does that make some sense?





>On Tue, 16 Jun 2009 19:51:56 -0500, sauravrt wrote:
>
>> Matlab command y1 = wgn(100,1,10) generates a column vector o

length
>> 100 containing real white Gaussian noise of power 10 dBW. How can I
>> verify that the power of the 100 samples is 10 dBW ?

>
>dBW? You mean "Decibels -- Watts"?
>
>If so, put the vector of numbers in a calorimeter for one second, and se


>if it registers one Joule of heat energy.
>
>--
>www.wescottdesign.com
>

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