Question

In the case of amplitude modulation to avoid distortion the modulation index $(\mu)$ should be:

• A. $\mu \leq 1$
• B. $\mu \geq 1$
• C. $\mu=2$
• D. $\mu=0$

Answer 1

The Correct Option is A

 To understand why the modulation index \(\mu\) should be \(\mu \leq 1\) in amplitude modulation, we need to delve into the concept of modulation. Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting audio signals using radio waves. It involves varying the amplitude of the carrier wave in line with the amplitude of the modulating (audio) signal.

The modulation index \(\mu\) is defined as the ratio of the amplitude change of the modulated wave to the amplitude of the carrier wave:

\(\mu = \frac{A_m}{A_c}\)

where \(A_m\) is the amplitude of the modulating signal, and \(A_c\) is the amplitude of the carrier signal.

In amplitude modulation, avoiding distortion of the transmitted signal is crucial for clear communication. The modulation index determines the degree of modulation applied to the carrier wave.

• If \(\mu \leq 1\): The modulated signal accurately represents the modulating signal without distortion. The carrier signal amplitude never goes to zero, indicating that the modulated wave stays within the envelope.
• If \(\mu > 1\): This results in over-modulation, where parts of the modulated signal distort because the carrier signal amplitude may drop to zero or negative, leading to signal inversion and envelope distortion.

Therefore, for accurate signal transmission and to avoid distortion, the modulation index should be kept less than or equal to 1.

Conclusion: The correct answer is that the modulation index \(\mu\) should be \(\mu \leq 1\), ensuring that there is no distortion in the amplitude modulation process.