Positive Phase Noise in Spectre PSS
I've been trying to simulate a simple differential LC oscillator, the one that is explained in Spectre PSS tutorial. However, it gives me positive phase noise at low frequency offsets(~ +50dBc@10Hz), (it gives acceptable negative phase noises for high frequency offsets: -130dBc@1MHz though).
I thought it might be because it couldn't find the exact fundamental freq. So, I gave it the exact fundamental tone I extracted from transient analysis. It didn't work...
Does anyone know if this is a Spectre problem or there is sth wrong with my simulation/circuit?
Hassan
Hi,
According to some papers that a I saw LC VCOs have below -100 dBc phase noise at 1Mhz offset for frequency carriers between 1Ghz and 2Ghz.
So, in your case, I think that your simulation in OK.
I think his question was about the +50dBc/Hz @ 10Hz. Wasn't it?
I think this is because the computing method uesed to calculate the phase noise was not accurate in low frequency.You can check the Cadence file about it.
According to the oscillator PN curve model, this sim results are not reasonable.
I think you should check the simulation setting.
I have this problem so, I simulated my ring oscillator by cadence and ADS but both results are same. I think it is because of software model and you should ignore it.
See https://www.edaboard.com/thread165472.html