Phase noise measurement-Need Help

[pinhead]

My work on CMOS LC-VCO design has problem, with its phase noise measurement.
Using Agilent E5052A signal source analyzer, I observe the unknwon noise source about 1/f^3, 1/f^2 frequency range.
The curve has never found (30dB, 20dB decrease), and phase noise trace is almost flat until 1MHz offset.

The measurement results are quite different from simulation results.

Did I mistake the measurement?
Do you give me any advice for this mistake?

 

[Grig]

Hello
Some noise source (not included in simulation) modulates your vco
Concider first dc suply noise and noise source on VCO control pin. Check this pins with spectrum analyzer for ex.
Your result is interesting for me too.