A speech signal of $3 \mathrm{kHz}$ is used to modulate a carrier signal of frequency $1 \mathrm{MHz}$,…

A speech signal of $3 \mathrm{kHz}$ is used to modulate a carrier signal of frequency $1 \mathrm{MHz}$, using amplitude modulation. The frequencies of the side bands will be
  1. $1.003 \mathrm{MHz}$ and $0.997 \mathrm{MHz}$
  2. $3001 \mathrm{kHz}$ and $2997 \mathrm{kHz}$
  3. $1003 \mathrm{kHz}$ and $1000 \mathrm{kHz}$
  4. $1.0 \mathrm{MHz}$ and $0.997 \mathrm{MHz}$

Solution

Frequency of carrier signal, $f_c=1 \mathrm{MHz}$ Frequency of message (speech) signal,
$f_m=3 \mathrm{kHz}=0.003 \mathrm{MHz}$
$\therefore$ Frequency of upper side band $=f_c+f_m$
$=1+0.003=1.003 \mathrm{MHz}$
Frequency of lower side band $=f_c-f_m$
$=1-0.003=0.997 \mathrm{MHz}$

Asked in: AP EAMCET 2020 (22 Sep Shift 2)

Practice more Communication System questions on Aicharya