rainsender
Newbie level 1
vco phase noise
I designed a 2.4GHz LC VCO using cadence. But the Spectre simulation gave me very large phase noise as shown in the figure. I know it's common to see positive phase noise using Spectre at low offset frequency. But what I got is more than 100 dBc. I tried to tighten the simulation Tolerance Options, 1e-5 for reltol, 5e-8 for vabstol, 1e-13 for iabstol, and selected gear2only as integration method, but there was little differnce. I also ran transient analysis and plotted the DFT to confirm the center frequency, and it turned out right. The current is around 6mA, which I think is large enough. I am a little crazy on this now. Anyone can explain this to me?
I designed a 2.4GHz LC VCO using cadence. But the Spectre simulation gave me very large phase noise as shown in the figure. I know it's common to see positive phase noise using Spectre at low offset frequency. But what I got is more than 100 dBc. I tried to tighten the simulation Tolerance Options, 1e-5 for reltol, 5e-8 for vabstol, 1e-13 for iabstol, and selected gear2only as integration method, but there was little differnce. I also ran transient analysis and plotted the DFT to confirm the center frequency, and it turned out right. The current is around 6mA, which I think is large enough. I am a little crazy on this now. Anyone can explain this to me?