Question

If F1 and F2 are the lower and upper cutoff frequencies of a band pass signal, then what is the condition to be satisfied to call such a band pass signal as narrow band signal?

(a) (F1-F2)>\(\frac{F_1+F_2}{2}\)(factor of 3 or less)

(b) (F1-F2)⋙\(\frac{F_1+F_2}{2}\)(factor of 10 or more)

(c) (F1-F2)<\(\frac{F_1+F_2}{2}\)(factor of 3 or less)

(d) (F1-F2)⋘\(\frac{F_1+F_2}{2}\)(factor of 10 or more)

The question was asked during an interview for a job.

Question is taken from Frequency Analysis of Discrete Time Signal topic in division Frequency Analysis of Signals and Systems of Digital Signal Processing

Answer 1

Right option is (d) (F1-F2)⋘\(\frac{F_1+F_2}{2}\)(factor of 10 or more)

The best I can explain: If the difference in the cutoff frequencies is much less than the mean frequency, the such a band pass signal is known as narrow band signal.