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Design >> Analog Design >> Low - Noise Oscillator Design - Topology selection ??
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Message started by Mayank on Nov 1^st, 2009, 10:16pm

Title: Low - Noise Oscillator Design - Topology selection ??
Post by Mayank on Nov 1^st, 2009, 10:16pm

Hi everyone,
I have to design a low-noise voltage-controlled oscillator.
Specs :---
Oscillation Freq. = 1GHz
Voltage Supply -- 1.2
Noise requirements -- around -55dBc @10kHz or lower
Max. Current Consumption @ 1.2 supply <= 2.5mA.

Any Suggestions please ??

--mayank.

Title: Re: Low - Noise Oscillator Design - Topology selection ??
Post by raja.cedt on Nov 1^st, 2009, 10:28pm

hi mayank,
i feel Phase noise spec seems very tough to achieve with ring oscillator so i feel LC is better but whats your Kvco or Tuning range.

Thanks,
rajasekhar.

Title: Re: Low - Noise Oscillator Design - Topology selection ??
Post by Mayank on Nov 1^st, 2009, 10:44pm

Hi,
Kvco is not a problem...Can be adjusted in both Ring Osci...as well as LC[LC offers low Kvco's v easily]..LC easily gives these specs..but it crosses the Area Limit...can't use so much Si real estate :(

Can't Ring Osci's satisfy these specs ??

--mayank.

Title: Re: Low - Noise Oscillator Design - Topology selection ??
Post by raja.cedt on Nov 1^st, 2009, 10:51pm

hi,
certainly you can do with ring oscillator but power you have to consider, so what i am suggesting is build some ring oscillator and vary power and check whether you are meeting power spec or not. I feel all these can be appreciated by simulation..not by any thing else

Thanks,
rajasekhar.

Title: Re: Low - Noise Oscillator Design - Topology selection ??
Post by Mayank on Nov 1^st, 2009, 10:58pm

Hi,
I have already tried out different topologies in RO design...Not achieving results, That's why i brought this up to the forum.
I have already tried out current-starved CCO, Differential CCO, CML topologies...All of them offer Low phase Noise at Lower Frquencies, but none of them are meeting my noise specs at around 1GHz....What i want to be sure is -- Are these topologies capable of giving such noise performance at given power levels & i am not designing them correctly , Or I can rule out ROs and go for LC?

Just wanna be sure to rule out Ring Osci....

regards,
Mayank.