Question

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

(a) -80dB/decade

(b) -40 dB/decade

(c) 40 dB/decade

(d) 80 dB/decade

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I'm obligated to ask this question of Bode Plots topic in chapter Frequency Response Analysis of Control Systems

Answer 1

Correct choice is (a) -80dB/decade

The explanation: A 4th order all pole system means that the system must be having no zero or s-term in numerator and s^4 terms in denominator. One pole exhibits -20dB/decade slope, so 4 pole exhibits a slope of -80 dB /decade.