How to improve phase noise of an oscillator

[geozog86]

Hello!

In cadence simulations, i got the basic components that create the phase noise of my oscillator:
-the biasing block seems to be the most responsible one (45% of the noise) , but how does that make any sense? It's a PTAT generator from which all currents are mirrored, but it's not in one of the crucial nodes for the oscillation frequency.
-some transistors in the biasing current source are responsible via their id and some via their fn. What does that imply?
-how can i improve the phase noise? As a general approach? I can only guess higher current? Is there any other general approach?

Thx for the help

 

[steadymind]

Re: Phase Noise Question

the noise from the bias devices can be mirrored to the main oscillating circuit causing poor phase noise.
add capacitor to ground/vdd on your bias nodes to act as a filter (you can implement gm-C filters also) this will help you reduce your flicker noise from the bias device by filtering.
increase your device sizes to decrease your noise, and increase current if available.