Narrowband FM

Approximation to AM, phasor representation.

Darshan N
Updated: 19 March 2026
10 min read

Narrowband FM Quiz

Test your knowledge of the NBFM approximation, its phasor form, and its spectral similarity to AM.

Question 1 of 3

Q1.The narrowband FM approximation expands s(t) = Ac*cos(2*pi*fc*t + beta*sin(2*pi*fm*t)) using cos(x+y) identity. For beta << 1, which of the following is the correct NBFM approximation?