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Question
In amplitude modulation, the modulation index m, is kept less than or equal to 1 because ______.
- m > 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
- m > 1 will result in overlapping of both side bands resulting into loss of information.
- m > 1 will result in change in phase between carrier signal and message signal.
- m > 1 indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.
Options
a and b
b and d
c and a
d and b
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Solution
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 (ma).
The modulation index (m) of amplitude modulated wave is m = `("amplitude of message signal" (A_m))/("amplitude of carrier signal" (A-c))`
If m > 1, then Am > Ac
In this situation, there will be the distortion of the resulting signal of amplitude modulated wave.
The maximum modulation frequency `(m_f)` of AM wave is
`m_f = (Δv_(max))/(v_m(max)) = "Frequency deviation"/"Maximum frequency value of modulating wave"`
If `m_f > 1`, then `Δv_(max) > v_m`
It means, there will be overlapping of both sidebands of a modulated wave resulting in loss of information.
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