In FM, frequency deviation is directly  proportional toSelect one:a. modulating frequencyb. carrier frequencyc. carrier amplituded. modulating signal amplitude

Break Down the Problem

1. Identify the relationship between frequency deviation and the factors stated in the options (modulating frequency, carrier frequency, carrier amplitude, modulating signal amplitude).
2. Understand the principles of frequency modulation (FM).

Relevant Concepts

1. In FM, the frequency deviation ($\Delta f$) represents how much the frequency of the carrier wave is varied based on the modulating signal.
2. Frequency deviation is primarily dependent on the amplitude of the modulating signal. The larger the amplitude, the greater the frequency deviation.

Analysis and Detail

1. Modulating Frequency: This impacts how rapidly the frequency changes but does not directly affect the degree of deviation.
2. Carrier Frequency: This is the base frequency that is modulated; it does not influence the deviation directly.
3. Carrier Amplitude: While it affects the power of the signal, it doesn't directly change the frequency deviation.
4. Modulating Signal Amplitude: This is the key factor in FM. According to Carson's Rule, the frequency deviation is proportional to the amplitude of the modulating signal.

Verify and Summarize

• After analyzing the factors that influence frequency deviation in FM, it is evident that the amplitude of the modulating signal is what directly impacts how much the carrier frequency deviates.

Final Answer

The correct answer is d. modulating signal amplitude.