Question

A frequency modulated signal with a carrier frequency of 10 MHz and a modulation index of 20 rad is to be generated using an indirect FM modulator shown in the figure below.

If the input message signal is a 15 kHZ sinusoid, then the maximum frequency deviation required at the output of the NBFM generator will be equal to kHz.

• A. 3

Answer 1

The correct option is A 3

Multiplication factor,
$n=\frac{f_{c2}}{f_{c1}}=\frac{10MHz}{{10}^{5}Hz}=\frac{{10}^7}{{10}^5}=100$

$\Delta f_2=\left({\beta }_2\right)\left(f_m\right)=\left(20\right)\left(15\right)kHz=300kHz$

$\Delta f_1=\frac{\Delta f_2}{n}=\frac{300}{100}kHz=3kHz$