Question

In amplitude modulation, the modulation index m, is kept less than or equal to 1 because ______.

1. m > 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
2. m > 1 will result in overlapping of both side bands resulting into loss of information.
3. m > 1 will result in change in phase between carrier signal and message signal.
4. m > 1 indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.

विकल्प

• a and b

• b and d

• c and a

• d and b

Answer 1

b and d

Explanation:

Modulation index: The ratio of change of amplitude of carrier wave to the amplitude of original carrier wave Is called the modulation factor or degree of modulation or modulation index (m_a).

The modulation index (m) of amplitude modulated wave is m = ${\displaystyle \frac{\text{amplitude of message signal}\left(A_m\right)}{\text{amplitude of carrier signal}(A-c)}}$

If m > 1, then A_m > A_c

In this situation, there will be the distortion of the resulting signal of amplitude modulated wave.

The maximum modulation frequency ${\displaystyle \left(m_f\right)}$ of AM wave is 

${\displaystyle m_f=\frac{\Delta v_{max}}{v_m(max)}=\frac{\text{Frequency deviation}}{\text{Maximum frequency value of modulating wave}}}$

If ${\displaystyle m_f>1}$, then ${\displaystyle \Delta v_{max}>v_m}$

It means, there will be overlapping of both sidebands of a modulated wave resulting in loss of information.