Dear Maryem, [quote userid="504246" url="~/cadence_technology_forums/f/custom-ic-design/43969/isf-function-extraction-in-cadence-virtuoso/1373736"]What I meant by "current source ISF" is for example we see in Hajmiri's paper ""Design Issues in CMOS Differential LC Oscillators"" that there is a separate ISF for the active transistors, and separate ISF with respect to Tail Transistor (current source for biasing). [/quote] [quote userid="504246" url="~/cadence_technology_forums/f/custom-ic-design/43969/isf-function-extraction-in-cadence-virtuoso/1373736"][/quote] This is what I meant by "nodes" in the circuit that does ViVa allows us to view these different ISFs with respect to different nodes? Or do we have to explicitly select the nodes first, the ones we are interested to see ISF for? I think you possibly may not fully appreciate the ppv that is computed by Spectre RF. Basically, the objective of an oscillator pss analysis followed by a pnoise analysis is to determine an estimate of the oscillator phase noise characteristic in light of its various device random noise sources and their frequency translation as a result of the non-linear action of the oscillator's large signal steady-state response. As such, there is not a "single" noise perturbation that is applied, but rather an ensemble of noise sources. Hence, the ISF or ppv provided represents the output phase perturbations due to ALL these noise sources - not simply a single impulse of charge as might be used when performing a set of conventional transient analysis as one varies the phase of the injected charge across the oscillator's period. This is discussed in the paper S. Levantino and P. Maffezzoni, "Computing the Perturbation Projection Vector of Oscillators via Frequency Domain Analysis," in IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, vol. 31, no. 10, pp. 1499-1507, Oct. 2012, doi: 10.1109/TCAD.2012.2194493. which is referenced in section " V. N OISE UPCONVERSION WITH Gammappv" of the paper entitled " A comparison of simulation strategies for estimating phase noise in oscillators" I referenced earlier. If you are interested in computing the ppv of a specific charge injection point, you will need to perform the far more intensive and time consuming set of conventional transient analyses in lieu of the time efficient analyses provided by spectreRF - not to mention the fact that end result may not truly represent the dominant noise sources contributing to oscillator phase noise. Does this help and did I answer your question with enough clarity (or did I not fully understand your inquiry)? Shawn
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