Question

In a Bode magnitude plot, which one of the following slopes would be exhibited at high frequencies by a $4^{th}$ order all-pole system ?

• A. $-80\text{dB/decade}$
• B. $-40\text{dB/decade}$
• C. $+40\text{dB/decade}$
• D. $+80\text{dB/decade}$

Answer 1

The correct option is A $-80\text{dB/decade}$

A 4th order all-pole system means that the system must be having no zero or s-terms in numerator and $s^4$ terms in denominator or 4-poles. i.e
$H\left(s\right)\propto \frac{1}{s^4}$
One pole exhibits $-20dB/decade$ slope. So, 4 pole exhibits a slope of $-80dB/decade$