Question

A system has poles at $0.01Hz,1Hz$ and $80Hz$ zeros at $5Hz,100Hz$ and $200Hz$. The approximate phase of the system response at$20Hz$ is

• A. $-{90}^{\circ }$
• B. $0^{\circ }$
• C. ${90}^{\circ }$
• D. $-{180}^{\circ }$

Answer 1

The correct option is A $-{90}^{\circ }$

Pole at $0.01$ and $1Hz$ gives $-{180}^{\circ }$ phase.
Zero at $5Hz$ gives $+{90}^{\circ }$ phase
$\therefore$ at $20Hz$ $+{90}^{\circ }$ phase shift is provided.