Does the VCO noise is reduced due to dividing ?

[RFCMOS]

VCO noise and divider

Assume you have a VCO @10GHz with a certain amount of phase noise @X kHz. then you divide the signal coming from the VCO by 2 with a noiseless divider.
Is the noise @X kHz of your divided signal (@5GHz) is reduced due the division?

 

[flatulent]

Re: VCO noise and divider

Yes. Multiplying and dividing the frequency also scales the noise level by the same amount.

 

[sunking]

VCO noise and divider

you can reference the theory about pll, and write the tran. function, you will get the anwser

 

[hanm]

Re: VCO noise and divider

Yes,of course.the phase noise is about 6dB smaller.

 

[gajen]

Re: VCO noise and divider

You can view it like this. Jitter is remaining same. As no noise is added and time period is doubled. So Phase noise is half. As same jitter for bigger period will translate to smaller noise

 

[pk3316]

VCO noise and divider

Divider the signal will improve the phase noise, multiply will degrade it.

 

[neoflash]

VCO noise and divider

I've ever wondered this question too.

THe key is that the transfer function of the divider is
1/N

 

[RFCMOS]

Re: VCO noise and divider

Hi all,

Is it correct to say that by divided the VCO frequency by a N divider, the VCO phase noise a frequency offset N*f from the carrier will become the Phase noise of the signal after division at a frequency offset f (N*f/N) from the carrier?
Thanks for your explanations.

 

[savithru]

how large is N=40 in PLL?

hi all,

From the deansbook on pll I read that N-counter value is the parameter which has largest impact on the Phase noise of a pll. The smaller this value is better the phase noise should be, as N values multiplies the noise.

Now I am using N=40.. Can you pls tell me , how large is my N value. To what extent this value affects my phase noise?

Pls reply

Thanks & Regards
SavithRu

 

[jfyan]

Re: VCO noise and divider

Yes,of course.the phase noise is about 6dB smaller.

yes ,you are right, but it is the case for dividing by 2.
jeff