Frequency deviation in Frequency Modulation (FM) refers to the amount of change in the carrier frequency produced by the modulating signal. It is defined as the difference between the instantaneous frequency of the modulated wave and the carrier frequency.

Here are key aspects of frequency deviation:

• Definition: The maximum change in frequency of the carrier signal from its unmodulated frequency, caused by the modulating signal.
• Units: Measured in Hertz (Hz) or Kilohertz (kHz).
• Formula: Δf = Kf * Am, where:
  • Δf is the frequency deviation.
  • Kf is the frequency sensitivity (Hz/V).
  • Am is the amplitude of the modulating signal.
• Significance:
  • Modulation Index: Frequency deviation is used to determine the modulation index (β) which is the ratio of the frequency deviation to the modulating signal frequency (fm), β = Δf / fm. The modulation index indicates the bandwidth and efficiency of the FM signal.
  • Bandwidth: Determines the bandwidth of the FM signal as defined by Carson's Rule: Bandwidth ≈ 2(Δf + fm) Source
  • Signal Quality: Affects the signal-to-noise ratio and overall quality of the FM signal.