SNR and modulated signal power (chirp)

Hi there,

Look at this code:

yn = chirp(T,f0,t2,f1,'quadratic');
noise = randn(size(yn));
y = yn + k*noise;

I need SNR:

SNR = 10*log10((1/sqrt(2))/k) [dB]

Is this correct? I assume that my signal power is 1/sqrt(2) and noise
power is k, but I'm not sure...

"WhoAmI" <michal@gosc.mine.nu> wrote in message 
news:3d-dna_WfNhQDITYnZ2dnUVZ_vidnZ2d@giganews.com...
> Hi there,
>
> Look at this code:
>
> yn = chirp(T,f0,t2,f1,'quadratic');
> noise = randn(size(yn));
> y = yn + k*noise;
>
> I need SNR:
>
> SNR = 10*log10((1/sqrt(2))/k) [dB]
>
> Is this correct? I assume that my signal power is 1/sqrt(2) and noise
> power is k, but I'm not sure...
>

This looks like matlab. If so type whos <CR>

- is yn complex?

Best of luck - Mike

>
>"WhoAmI" <michal@gosc.mine.nu> wrote in message 
>news:3d-dna_WfNhQDITYnZ2dnUVZ_vidnZ2d@giganews.com...
>> Hi there,
>>
>> Look at this code:
>>
>> yn = chirp(T,f0,t2,f1,'quadratic');
>> noise = randn(size(yn));
>> y = yn + k*noise;
>>
>> I need SNR:
>>
>> SNR = 10*log10((1/sqrt(2))/k) [dB]
>>
>> Is this correct? I assume that my signal power is 1/sqrt(2) and noise
>> power is k, but I'm not sure...
>>
>
>This looks like matlab. If so type whos <CR>
>
>- is yn complex?
>
>Best of luck - Mike
>
>
>
>
>
Yes, this is matlab code of course. yn is not complex, because this is FM
modulated signal with quadratic frequency modulation.

Assuming, that yn amplitude is 1, I think that its power is 1/sqrt(2). but
I'm not sure how to obtain noise power.

I think, that noise power is k^2 (variance), but I'm not sure if is it
correct....