Communication System — DU B.Sc. (Hons) Physics Previous Year Question Papers

Name of the Department Department of Physics and Astrophysics B.Sc. Hons._(Physics)_ NEP: UGCF-2022 Communication Systems (DSE paper) Question paper Set number : Set I (a) State the difference between analog and digital modulation. Give one example of each. (b) Determine the percent power saving when the carrier wave and one of the sidebands is suppressed in an AM wave modulated to a depth of 50%. (c) Explain the need for modulation in communication? (d) Draw PPM and PWM wave forms for a sinusoidal modulating signal. (e) Why is the uplink frequency kept higher than the downlink frequency in satellite communication? (f) What information is contained in the SIM number? (a) Define Amplitude Modulation (AM) and write mathematical expressions for AM. The output signal from an AM modulator is. VAm (t) = 5 cos(1800Tt) + 20 sin(2000rtt) - 5 cos(2200nt) Determine the following. (i) Frequency and amplitude of modulating signal (ii) Frequency and amplitude of carrier signal (iii) Modulation index Ratio of the power in the sidebands to the power in the carrier. (7) (b) Define the two types of angle modulation. (2) (c) A single tone modulating signal cos (15 it 10° t) frequency modulates a carrier of 10 amplitude of the modulating signal. Assume kj=1SKHz /volt. (a) State and prove sampling theorem. Calculate the Nyquist rate and sampling frequency for analog signal is expressed by the equation x(t) = 5 cos(100mt) + 10 sin(500ntt) - 8 cos(300ntt) (b) What is Pulse Amplitude Modulation (PAM)? Draw the circuit of a Pulse Amplitude (8) modulator and explain its working. List the disadvantages of PAM. (a) Sketch ASK, FSK and BPSK waveforms for the sequence: 1011011010. (3) (b) Describe in detail the three basic operations involved in Pulse Code Modulation. (6) (Distinlein even Time Division Multiplexing (TDM) and Frequency Division