Question

Bode magnitude plot of a system is 0 dB and its maximum phase is -180 degree. Possible transfer function of the system is 
1. \(\frac{{s - 1}}{{1 + s}}\)
2. \(\frac{1}{{{s^2}}}\)
3. \({e^{ - s\tau }}\)
4. None of these

Answer 1

Correct Answer - Option 1 : \(\frac{{s - 1}}{{1 + s}}\)

Let consider the option (a)

Transfer function is, \(\frac{{s - 1}}{{1 + s}}\)

Bode magnitude plot of the system = 0 dB

Phase angle, \(\phi = {\tan ^{ - 1}}\left( { - \frac{1}{1}} \right) - {\tan ^{ - 1}}1\; = - 135^\circ - 45^\circ = - 180^\circ \)