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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Communication System

NTA Abhyas 2020 · Physics · Communication System

What is the modulation index of an FM signal having a carrier swing...

What is the modulation index of an FM signal having a carrier swing of 100kHz100kHz when the modulating signal has a frequency of 8kHz8kHz?

Options

  1. A

    6.256. 25

  2. B

    6.236. 23

  3. C

    6.556. 55

  4. D

    6.336. 33

Correct answer

A.

6.256. 25

Step-by-step solution

Given: Carrier Swing =100kHz= 100kHz

fa=8kHz{f}_{a} = 8kHz

From the defining equation,

mf=∆ffa{m}_{f} = \dfrac{∆ f}{{f}_{a}}

First determining ∆f∆ f ,

∆f=CarrierSwing2∆ f = \dfrac{CarrierSwing}{2}

=100×1032= \dfrac{100 \times {10}^{3}}{2}

=50kHz= 50kHz

Now substituting into the equation for mf{m}_{f}

mf=50×1038×103{m}_{f} = \dfrac{50 \times {10}^{3}}{8 \times {10}^{3}}

=6.25= 6.25
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