Question

An FM wave is given as $s\left(t\right)=20\sin (6\times {10}^{8}t+7\sin (1250t\left)\right)$ the maximum frequency deviation of the FM signal is equal to

• A. 199 Hz
• B. 4.375 kHz
• C. 1.393 kHz
• D. 2.143 kHz

Answer 1

The correct option is C 1.393 kHz

$s\left(t\right)=A\sin [{\omega }_{c}t+m_f\sin ({\omega }_{m}t\left)\right]$

$s\left(t\right)=20\sin [6\times {10}^{8}t+7\sin (1250t\left)\right]$

$\therefore f_m=\frac{{\omega }_m}{2\pi }=\frac{1250}{2\pi }\approx 199Hz$

$\therefore \Delta f=m_f{f}_m=7\times 199=1.393kHz$