Question 6.4: Determination of the Break Frequency for a Highpass Filter S...

Recall that the low-frequency asymptote slopes at a rate of 20 dB/decade. Thus, we must select f_B to be

\frac{30 \ dB}{20 \ dB/\text{decade}} = 1.5 \text{ decades }

higher than 60 Hz. Employing Equation 6.17, we have

\mathrm{ number~of~decades }=\log{\left( \frac{f_2}{f_1} \right) }            (6.17)

\log{\left( \frac{f_B}{60} \right) }=1.5

This is equivalent to

\frac{f_{B}}{60}=10^{1.5}=31.6

which yields

f_B \cong 1900\mathrm{~Hz}