Katwa College

Department of Electronics

B.Sc. Semester-IV Internal Examination 2024

Core Course-1D: Communication Systems

Answer any two questions.                                                                                         2×5=10

1. a) What is the need for modulation?                                                                          3

b) Define the term modulation index for AM.2

2. a) What do you mean by i) modulating wave and ii) modulated wave?                    2

b) Draw the wave form of an amplitude-modulated signal when the carrier and the modulating signals are sinusoidal. How can you obtain modulation index from this waveform?3

3. Show that the total power for a fully amplitude modulated wave is 1.5 times the unmodulated carrier power.                                                                                                5

4. The peak-to-peak value of an AM voltage has a maximum value of 8 V and a minimum value of 2 V. What is the percentage modulation and the amplitude of the unmodulated carrier?                                                                                                              5