(SEM V) THEORY EXAMINATION 2024-25 ANALOG & DIGITAL COMMUNICATION

Subject Code: BEE058

Subject Name: Analog & Digital Communication

Exam Type: Theory

Semester: V (Fifth Semester, B.Tech)

Maximum Marks: 70

Duration: 3 Hours

Exam Year: 2024–25

Sections: A, B, and C

SECTION A – Short Answer Questions (2 × 7 = 14 Marks)

Attempt all questions. Each carries 2 marks.

Define modulation, amplitude modulation, and angle modulation.

Draw the basic block diagram of an analog communication system.

Explain frequency deviation of an FM signal.

Explain Nyquist criteria for sampling.

Why is FSK preferred over ASK?

What do you understand by the Shannon–Hartley theorem?

What is an electronic commutator in a TDM system?
 

SECTION B – Medium-Length Questions (7 × 3 = 21 Marks)

Attempt any three of the following.

Differentiate between narrowband FM and wideband FM with frequency spectrum and mathematical expressions.

Explain coherent generation and detection of PAM signals with suitable equations.

Define quantization and explain quantization and coding with diagrams.

Explain time-division multiplexing (TDM) — distinguish between synchronous and asynchronous TDM.

Draw the block diagram of a BPSK transmitter and explain the balanced ring modulator used in BPSK.
 

SECTION C – Long/Analytical Questions (7 × 5 = 35 Marks)

Attempt one part from each question.

Q3

a. Why is a superheterodyne receiver better than a TRF receiver? Discuss the functions of a receiver.
b. With a neat diagram, explain the generation and detection of an SSB-SC wave.

Q4

a. What is noise? Explain why it cannot be eliminated completely but can be minimized.
b. An FM modulator operates at 500 kHz with 10V amplitude and frequency deviation of 10 kHz. For a modulation index of 1, compare minimum bandwidth using Bessel’s function and Carson’s rule.

Q5

a. Explain delta modulation and how adaptive delta modulation improves performance.
b. Explain generation and demodulation of pulse-width modulation (PWM).

Q6

a. A discrete memoryless source has symbols with probabilities (0.40, 0.20, 0.20, 0.10, 0.10). Construct a Huffman code and calculate its efficiency.
b. Draw optimum receiver structures for DPSK and coherent FSK, showing modulated waveforms and probability of error.

Q7

a. Define information and entropy. Derive an expression for channel capacity of a continuous channel.
b. Explain the PCM–TDM system and the desirable features of a T1 carrier system.
 

Key Topics for Revision

Types of modulation: AM, FM, PM                              Difference between narrowband & wideband FM

Quantization, Sampling theorem, and TDM                BPSK transmitter and balanced modulator

Superheterodyne receiver structure and working       Noise minimization techniques

Delta modulation vs Adaptive delta modulation        Shannon–Hartley theorem and channel capacity

Huffman coding and entropy calculation                   PCM and T1 carrier system

Quick Study Tips

Revise basic block diagrams: AM/FM system, PCM-TDM, receiver circuits.

Practice numerical problems: FM bandwidth, quantization efficiency, Huffman code.

Understand digital modulation schemes (ASK, FSK, PSK, DPSK).

Memorize Shannon theorem and Carson’s rule derivations.

Draw and label signal waveforms (PAM, PWM, PPM, FM, SSB-SC).