What does FM stand for and what does it do?

• A. Amplitude Modulation
• B. Frequency Modulation
• C. Phase Shift Keying
• D. Amplitude Shift Keying

Answer: (B)

FM stands for Frequency Modulation. It varies the carrier frequency in proportion to the instantaneous value of the modulating signal, while the carrier’s amplitude stays essentially constant. As the modulating signal increases, the carrier frequency shifts higher; as it decreases, it shifts lower. Information is carried in these frequency deviations rather than in changes to amplitude. This makes FM more resistant to amplitude noise and fading, improving audio and other communications. It differs from amplitude modulation, where the carrier’s amplitude varies with the signal, and from schemes that encode data in phase or amplitude changes like phase shift keying or amplitude shift keying.