The phase noise chaterstics at output of frequency multiplier

[pll_boy]

hi all,

i have a oscillator followed by frequency multiplier, i wanted to know the phase noise chaterstics at output of frequency multiplier.

i use cadence for simulation of my circuit,

problem is chosing the oscillator i am getting diffrent Phase noise charaterstic when i choose 1)oscillator as oscillator
2)frequency multiplier output as oscillator
can u tell me what is the write output(oscillator) to choose

 

[haadi20]

multiplier phase noise

Ofcourse, the phase noise will be different at the Oscillator output and the Multiplier output (due to change in frequency) and the difference depends on the Multiplication factor you are using.

Ideally, if your multiplying by 2, the Phase Noise after the multiplier should be 6 dB higher than the phase noise at the output of oscillator.

You should use the Multiplier output as "oscillator" in simulation settings...

Hope this helps..

 

[dhasmana]

phase noise analysis

Hi,

I I am doing Phase Noise Sim for a VCO then there is no input freq. source.What value should I give for the beat frequency?
Regards,
Jitendra.

 

[haadi20]

mutiplier phase noise

You have to run a PSS simulation before the PNoise simulation. PSS will determine the exact oscillation frequency. You can enter a value close to your intended oscillation frequency, as the beat frequency.

Lastly, you do not require a frequency source for Phase noise analysis. Only the output nodes of the VCO can be mentioned as inputs for phase noise calculation.

 

[pll_boy]

frequency multiplier phase noise

Thanks haadi
I am measuring phase noise at output of frequency multplier
problem is when in PSS analysis i have to chose oscillator node,
so my Question is what oscillator nodes i have to choose in pss analysis,is it oscillator output or frequency multiplier output(for both i am getting diffrent phase noise results what is the correct one)
and why

 

[haadi20]

phase noise and multipliers

You have to chose the Multiplier outputs as oscillator nodes in the PSS simulation. This is because in the next calculation of the phase noise, it will take the calculated carrier frequency from the PSS (in this case multiplier output) and find the phase noise around that carrier...

I hope it is clear now...

Regards...