Question

Which of the following is true about a conventional AM wave?

• A. The negative frequency in the mathematical expression is due to the pressure of two frequency component of message signal.
• B. Carrier power is independent of modulation index whereas sideband power and total power increases with increase in modulation index.
• C. The total power carried by the sidebands is ${\mu }^2$ times the power carried by carrier signal.
• D. The portion of the spectrum of AM wave lying above the carrier frequency ${\omega }_C$ is called as upper sideband.

Answer 1

Answer: (B), (D)

The portion of the spectrum of AM wave lying above the carrier frequency ${\omega }_C$ is called as upper sideband.

$P_{SB}=\left(\frac{{\mu }^2}{2}\right)P_C$

The negative frequencies are due to the use of exponents in mathematical operation.
$P_c$ is independent of $\mu$ but $P_{SB}$ depends on $\mu$
$\uparrow P_{total}=P_c+P_{SB}\uparrow$