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Sep 22nd, 2020, 8:59pm
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 Question on Hajimiri-Lee model (Read 1124 times)
 iVenky Community Member Offline Posts: 93 Silicon Valley Question on Hajimiri-Lee model Feb 03rd, 2019, 11:47pm   I am reading the Hajimiri-Lee phase noise model, and got a question on that. If you have an LC tank circuit that is free-running and I inject a current i(t) (dirac current) at instants either t1 or t2 (shown in the figure), depending on when you inject the phase of the output changes (as shown). If I inject it at t1, then phase of the output changes while if I inject it at t2 only the amplitude changes but not the phase. What I don't understand here is when I inject the current i(t) at instant t1, shouldn't the amplitude also change just by superposition of oscillation waveform and the input i(t) energy? This is the part that's confusing to me. And what happens if I inject a really large i(t) that the delta voltage step at t1 exceeds the initial peak voltage to begin with, would the amplitude still change?In the dV/dt and V plot, t1 corresponds to 'b' and t2 corresponds to 'a'. Back to top Life is a nonlinear system. The goal is to find a solution with the least error and not an exact solution.   IP Logged
 Ken Kundert Global Moderator Offline Posts: 2285 Silicon Valley Re: Question on Hajimiri-Lee model Reply #1 - Feb 4th, 2019, 1:10am   You are correct. The Hajimiri-Lee model is not to be taken too literally. It is more a conceptual/intuitive explanation. The impulses are assumed to be small.-Ken Back to top IP Logged
 Geoffrey_Coram Senior Fellow Offline Posts: 1986 Massachusetts, USA Re: Question on Hajimiri-Lee model Reply #2 - Feb 6th, 2019, 6:51am   It's intuitive, but not always right:https://ieeexplore.ieee.org/abstract/document/933331/ Back to top If at first you do succeed, STOP, raise your standards, and stop wasting your time.   IP Logged
 iVenky Community Member Offline Posts: 93 Silicon Valley Re: Question on Hajimiri-Lee model Reply #3 - Feb 6th, 2019, 8:09am   Thanks for the replies. Back to top Life is a nonlinear system. The goal is to find a solution with the least error and not an exact solution.   IP Logged
 iVenky Community Member Offline Posts: 93 Silicon Valley Re: Question on Hajimiri-Lee model Reply #4 - Feb 21st, 2019, 10:41pm   1) While reading about the model again, the author mentions that the ISF is a dimensionless quantity. If you consider this expression (attached), I feel that ISF function Γ(ωτ) has a unit of radians otherwise, I don't see the equation balance on both sides. Is this right?2) Also, does the ISF change with the Q factor of LC tank? It's interesting that the expression that the author derives is only for an ideal lossless tank. Back to top Life is a nonlinear system. The goal is to find a solution with the least error and not an exact solution.   IP Logged