Help with VCO Phase noise analysis with SpectreRF

[frank_8017]

spectrerf manual

Hello,

I am currently simulating the phase noise of a VCO wih cadence spectreRF AA simulation tool. I have read the help files of AA concerning the phase noise simulation of oscillators and cadence's whitepaper "oscnoise.pdf" available on the net.

The problem which I am having is the following:

What exactly is the meaning of a "sideband" (referred by the "maxsidebands" field located in the PNOISE form)?

In the help file,a sideband Ki is defined by the following equation:
f(noisesource)= f(out)+ Ki*fund(pss)
Does this mean that a sideband defines the noise frequencies which are used in the computation of the PN around the desired harmonic of the output?

According to the help files, one should set the maxsideband field to 0 (at least for PN of oscillators). Shouldn't one set the maxsidebands field to a large number as to evaluate the PN due to all sidebands (whatever they are)?

My problem is that my results improve by 40dBs when I shitch from a "maxsidebands" of 0 to a "maxsidebands" of 1 ?
I would like to know which of the the results is the real one.

Any help will be appreciated.
Regards
-Frank

 

[alastair41]

maxsidebands noise

That specifies how many harmonics you want to include. There is a very good tutorial on this in the manual.

 

[frank_8017]

noise analysis of vco

Hello,

I thougth the number of harmonics you want to unclude are specified by the "number of harmonics" field found in the PSS analysis form.
I am still confused about the exact nature of the sidebands in PNOISE analysis.

-Frank

 

[lyrix]

spectrerf beat frequency

First of all, on the SpectreRF Theory, it is refering to the increase of maximum sideband (same as harmonics) which means that an increase of maximum sideband will take care of the noise contributed by the various harmonics. It is important that the number of harmonics settings in PSS should be equal to or more than the settings of the PNoise maximum sideband.

I think that maximum sidebands is bigger the better for accuracy but it take longer runtime. Take note of PSS settings and note that your settings should never exceed the maxacfreq settings in PSS.

 

[amarnath]

spectrerf theory

hello everybody,what di u mean by beat frequency in pss analysis in spectre,is it ur oscillator output frequency?also is a standalone analysis of the vco phase noise enough or u need to calculate the phase noise when the pll is a part of the system.i am unable to calculate phase noise of vco as a part of the pll system,cause spectre says my inout clk signal is periodic and so pss and pnoise cannot be performed.please give ur suggestions on this .

regards
amarnath