Which modulation is more resistant to noise and interference?

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

Answer: (C)

Noise resistance comes from how the information is carried by the signal. In amplitude-based schemes, the data sits in the envelope of the carrier, so random amplitude fluctuations from noise directly distort the information. In the digital amplitude scheme, the data is encoded in amplitude levels, which makes it even more vulnerable to amplitude disturbances. In frequency modulation, the data is carried by how fast the carrier’s phase changes over time, not by its height. The amplitude remains almost constant, so typical noise that alters amplitude doesn’t hide or erase the encoded frequency deviations. The demodulator then recovers the data from these frequency changes, making the system much less sensitive to amplitude noise and many kinds of interference. Phase-based schemes can be robust too, but they rely on maintaining accurate phase information and synchronization, which can be more challenging in noisy conditions. Because of the constant envelope and the way information is embedded in frequency, frequency modulation tends to be more resistant to noise and interference than the amplitude-based options.