ISF Simulation using Transient Analysis by injecting Impulse

Hi ,

I am trying to get the Impulse Sensitivity function for Ring Oscillator  so I am trying to follow the below steps:

i) First I am simulating the oscillator unperturbed and get the unperturbed waveform.

ii) Then I am injecting small current impulses at time instant t1, between nodes of interest with an area del q. So as a result I am getting oscillator output shifted in time domain depending upon at what time instant I am injecting the impulse current.

iii)Then I repeat the step 2 for N number of times in one period to get different N waveforms (link below)

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So I want to know is there a way in cadence in which I can find del t  i.e find time shift occurred  due to current injection for N different outputs . and plot the ISF in the same window using the formula (2*pi/T0)*(del q/Qmax).

Thanks