Hi everyone.
When plotting the closed loop stability analysis, what happens if the gain crosses the 0dB more than once? Say, three times?
The same for the phase margin plot, what happens of it "crosses" the 0deg more that once?
Regards.
if the open-loop gain is higher than 1 (=0dB) and the phase shift is higher than 180° at the same frequency of the open-loop characteristic your system is unstable.
you don't need to plot Nyquist-curve to check this, just go through the magnitude and phase points and check the above condition.
For specifically that example it is not necessary.The point is that for loop gain functions with more than one crossing of the 0 dB line, you need to evaluate the full Nyquist criterion.
Which example? The original post doesn't specify a scenario.For specifically that example it is not necessary.
Not sure how frequency can be expressed in degree.if the gain is less than 1 (0 dB) at all following frequencies: -180º-n*360º ("n" is natural number including 0).
Your example. The one that has multiple gain crossover frequencies.Which example? The original post doesn't specify a scenario.
The gain must be evaluated at frequencies of the loop gain that has the phase equal to -180º-n*360º ("n" is natural number including 0).Not sure how frequency can be expressed in degree.
I don't see that the question is restricted to the trivial case k=0 (no encirclements of the critical point). In the more interesting, and less intuitively understandable cases your condition is not fulfilled but the system is conditionally stable, though.For specifically that example it is not necessary.
Plot real part vs imaginary part of the quantity of interest. AC analysis needed.do you guys now if it is possible to simulate nyquist or better saying, plot nyquist in cadence/spectre?
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