Correct Answer - Option 4 : -180°
Concept:
Each zero at origin gives a phase shift of + 90°
For N zeros at origin gives a phase shift of + 90N°
Each pole at origin gives a phase shift of - 90°
For N poles at origin gives a phase shift of - 90N°
Calculation:
The given transfer function = 1/s2
Number of poles at origin = 2
Phase shift = 2 × (- 90°) = - 180°
Minimum phase system: It is a system in which poles and zeros will not lie on the right side of the s-plane.
For a minimum phase system:
\(\mathop {\lim }\limits_{\omega \to \infty } \angle G\left( s \right)H\left( s \right) = \left( {P - Z} \right)\left( { - 90^\circ } \right)\)
Where P & Z are finite no. of poles and zeros of G(s)H(s)
Non-minimum phase system: It is a system in which some of the poles and zeros may lie on the right side of the s-plane.
In particular, zeros lie on the right side of the s-plane.
All pass system: An all-pass network is the network that is the combination of the minimum and non-minimum phase systems and have the unity magnitude for all
frequencies and imparts only a 180-degree phase shift. The pole and zero of an all-pass filter are at the same distance from the origin.