Question

A signal of frequency \(3\,\text{kHz}\) is amplitude modulated on a carrier wave of frequency \(2.5\,\text{MHz}\). The upper and lower sideband frequencies in the resultant signal are

• A. \(2500\,\text{kHz}, 2503\,\text{kHz}\)
• B. \(2503\,\text{kHz}, 2497\,\text{kHz}\)
• C. \(2.5\,\text{MHz}, 3\,\text{kHz}\)
• D. \(5.5\,\text{MHz}, 0.5\,\text{MHz}\)

Hint:

In AM, sidebands always appear at \(f_c \pm f_m\).

Answer 1

The Correct Option is B

Step 1: Identify carrier and modulating frequencies.
\[ f_c = 2.5\,\text{MHz} = 2500\,\text{kHz}, \quad f_m = 3\,\text{kHz} \]

Step 2: Sideband frequencies.
Upper sideband: \[ f_c + f_m = 2503\,\text{kHz} \] Lower sideband: \[ f_c - f_m = 2497\,\text{kHz} \]