Question

Audio sine waves of $3kHz$ frequency are used to amplitude modulate a carrier signal of $1.5MHz$. Which of the following statements are true?

• A. The side band frequencies are 1506 kHz and 1494 kHz
• B. The bandwidth required for amplitude modulation is 6 kHz
• C. The bandwidth required for amplitude modulation is 3 MHz
• D. The side band frequencies are 1503 kHz and 1497 kHz

Answer 1

Answer: (B), (D)

${\omega }_m=3kHz,{\omega }_c=1.5MHz=1500kHz$
Side band frequencies $=\left({\omega }_c-{\omega }_m\right)$ and $\left({\omega }_c+{\omega }_m\right)$
$=(1500-3)kHz$ and $(1500+3)kHz$
$=1497kHz$ and $1503Hz$
Bandwidth $=2{\omega }_m=2\times 3=6kHz$