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What is the factor to be multiplied to the dc gain of the filter to obtain filter magnitude at cutoff frequency?(a) 1(b) √2(c) 1/√2(d) 1/2I got this question in an online interview.I would like to ask this question from Butterworth Filters in chapter Digital Filters Design of Digital Signal Processing

Answer» CORRECT ANSWER is (C) 1/√2

The best I can explain: The dc gain of the filter is the filter magnitude at Ω=0.

We know that the filter magnitude is given by the equation

|H(jΩ)|=\(\frac{1}{\SQRT{1+(\frac{Ω}{Ω_C})^{2N}}}\)

At Ω=ΩC, |H(jΩC)|=1/√2=1/√2(|H(jΩ)|)

THUS the filter magnitude at the cutoff frequency is 1/√2 times the dc gain.


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