THEORY EXAMINATION (SEM-V) 2018-19 PRINCIPLES OF COMMUNICATION

B.Tech | Semester V | Important Questions & Notes (Section-wise)

 SECTION A – Very Short Answer (Important for 1–2 marks)

These questions test basic definitions and formulas. Prepare crisp answers.

Important Questions

What is codeword length?                            Define transmission bandwidth.

What is bit rate?                                             Define signal-to-quantization noise ratio (SQNR).

What is sampling theorem?                          Define quantization.

What is modulation?                                     Define noise in communication systems.

Quick Notes

Codeword length: Number of bits used to represent one sample.

Bit rate = Number of bits transmitted per second (bps).

Transmission bandwidth: Range of frequencies required to transmit a signal.

SQNR: Ratio of signal power to quantization noise power.

These questions are formula-based or definition-based, so answers must be short and precise.

SECTION B – Short Answer (5–7 marks type)
 

These questions require explanation + diagram or formula.
 

Important Questions
 

Explain Pulse Code Modulation (PCM).

Explain quantization noise and its effect.

Describe the sampling process in communication systems.

Explain delta modulation with advantages and limitations.

Explain the need for modulation in communication systems.

Important Notes

PCM steps: Sampling → Quantization → Encoding

Quantization noise occurs due to finite number of levels.

Sampling theorem: Sampling frequency ≥ 2 × highest signal frequency.

Delta modulation uses 1-bit encoding but suffers from slope overload and granular noise.

Always include a block diagram if possible.

SECTION C – Long Answer (10–14 marks, Most Important)

These questions are high-weight and compulsory for deep understanding.

Most Important Question

1. Define Figure of Merit. Derive the mathematical expression of Figure of Merit for FM system.

Key Notes for Answer

Figure of Merit (FOM) =

• FOM=(S/N)output(S/N)input\text{FOM} = \frac{(S/N)_{output}}{(S/N)_{input}}FOM=(S/N)input​(S/N)output​​

In FM, FOM improves with modulation index (β).

For FM:

• FOMFM=32β2\text{FOM}_{FM} = \frac{3}{2} \beta^2FOMFM​=23​β2

FM offers better noise immunity compared to AM.

Include derivation steps, assumptions, and final result.