Question

A carrier wave of frequency 2.5 GHz is amplitude modulated with two modulating frequencies equal to 1 kHz and 2 kHz. The modulated wave will have the total bandwidth:
1. 6 kHz
2. 2 kHz
3. 4 kHz
4. 3 kHz

Answer 1

Correct Answer - Option 3 : 4 kHz

Concept:

For multitoned modulation, the bandwidth is equal to twice the highest modulating frequency.

Bandwidth = 2 f_m

f_m = max(f_m1, f_m2)

Where f_m1 and f_m2 are modulating frequencies.

Calculation:

The given modulating frequencies are:

f_m1 = 1 kHz, f_m2­ = 2 kHz

f_m = max(f_m1, f_m2) = 2 kHz

Bandwidth = 2 × 2 = 4 kHz