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I designed some analog second-order all-pass filter in LTspice and provided Monte Carlo analysis as well. I want to evaluate the obtained AC results with .meas command, particularly:

  1. Magnitude variation at pole frequency (.meas AC 'label' FIND mag(V(out)) AT 'freq value of interest') - this is done
  2. Pole frequency variation at -180°, which I would expect as '.meas AC 'label' FIND frequency AT ph(V(OUT))=-180', however it does not return anything. Could anybody help please?
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  • \$\begingroup\$ The phase is asymptotic, so it will never reach full +/-180deg. This is particularly true for comparing floating point numbers (which you have). The only thing to do is to manually calculate the phase at, say, one decade earlier/later, then using the .MEAS card with >= or <= (not just < or >). Just a thought. \$\endgroup\$ – a concerned citizen May 17 at 5:38

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