hello buddypoor,
yes you are correct, but here PM and gain margin doesn't look good, infact stability margin (means how close your nyquist plot to (-1,0) point) would give better result.

Thanks.
Raj.

Hi RAJ,

here is an additional information - perhaps it is new for you:

The mentioned vector margin (min. distance between T(s) and "1" in the Nyquist plane) can be easily found:

Display 1/abs(1-T(s)) and find the maximum of this curve.
The inverese of this maximum gives this stability measure.
In your example: margin app 1/3.85 which is rather poor.
(T(s) is the real loop gain - including sign inversion at the summing node).

hello rajkumar,
yes, for all pole systems (or monotonic mag and phase responce) you can apply bode with out any issue. You can refer this book for all the details "Feedback Systems: An Introduction for Scientists and Engineers ".

@buddypoor: do you know any simulator which can plot Nyquist plot, i know LTspice can.

Thanks,
Raj.