Analog & Digital Communication (IT-404) - Important Questions

Differentiate between energy and power signals and classify given signals / standard signals as energy or power

Define and illustrate linear/non-linear, time-invariant/variant, causal/non-causal, and stable/unstable systems with examples.

Draw the block diagram of a basic communication system and explain the function of each block.

Find the Fourier Transform of the gate function, unit step function and delta function.

State the properties of the Fourier transform and determine the Fourier transform of a unit impulse and a constant.

Write a short note on any two:

Define signal and differentiate between analog and digital signals

Draw the block diagram of a communication system, explain each block, and define a signal with its types (continuous/discrete, deterministic/non-deterministic, periodic/non-periodic).

Write down the function of the unit impulse function. also evaluate $x(t) = \int_{0}^{5} \delta(t) \sin 2\pi t \, dt$

Calculate and plot the frequency response $H(\omega)$ of a causal LTI system with impulse response $h(t) = e^{-2t}u(t)$ using the Fourier transform.

Explain the rectangular pulse, triangular pulse, and signum functions with expressions and waveform diagrams.

Classify signals and explain each type with waveform diagrams and mathematical expressions

Explain the block diagram and working of a superheterodyne receiver, including sensitivity and selectivity.

Explain the generation/working of AM using square-law modulator with circuit diagram and waveforms.

Given carrier amplitude/power and modulation depth, calculate modulation index, sideband frequencies, bandwidth, sideband power, total power and transmission efficiency.

Explain the design, operation and block diagram of a TRF receiver and its limitations compared to a superheterodyne receiver.

Compare DSB-SC, SSB-SC and VSB-SC modulation techniques on the basis of bandwidth, power requirement and other characteristics.

Define the modulation index of an AM wave and draw the frequency spectrum of a DSB-FC signal.

Define sensitivity, selectivity and fidelity of a radio receiver.

Write short notes on VSB-SC systems, M-ary PSK, receiver characteristics, Fourier Transform and properties.

Discuss square-law and switching modulators for AM generation with circuit diagrams and waveforms.

Describe DSB-SC and SSB-SC systems with block diagrams.

Given message and carrier signals for amplitude modulation, calculate modulation index, sideband frequencies, bandwidth required, and total power delivered to load.

Explain DSB-SC modulation and its advantages and disadvantages compared to conventional AM.

Explain the direct and indirect methods of FM generation, including block diagrams, working principles and advantages.

Define/explain frequency deviation, modulation index and deviation ratio in FM

Calculate FM modulation index and bandwidth from given carrier, deviation and modulating frequency, and state the difference between FM and PM.

Explain the operation of the Foster-Seeley discriminator as an FM demodulator with schematic/circuit diagram and phasor/phase diagrams.

Explain angle modulation, its significance, and its types (frequency modulation and phase modulation) with expressions and waveforms.

Explain the function/operation of the ratio detector for FM demodulation with circuit diagram.

Explain the phenomenon of pre-emphasis and de-emphasis in FM systems. Derive transfer functions for both.

Explain frequency deviation, percent modulation, phase deviation and modulation index in angle modulation with example

Discuss the advantages and disadvantages of the direct method compared to the indirect method of FM generation.

Explain deviation ratio and its significance in FM and calculate deviation ratio given frequency deviation and modulating frequency

Explain the balanced slope detector for FM demodulation with schematic diagram and characteristic/response diagram.

Explain indirect frequency synthesis using Phase Locked Loop (PLL) and the working principle of PLL in FM generation.

State and prove the sampling theorem for low-pass signals, including Nyquist rate and effect of undersampling (aliasing).

Explain Delta Modulation (DM) and Adaptive Delta Modulation (ADM) in detail, including merits and demerits.

State the sampling theorem for low-pass signals and distinguish between natural sampling and flat-top sampling.

In a PCM system, a signal band-limited to 3.4 kHz is sampled at 8 kHz and encoded using 8 bits per sample. Determine the bit rate and the signal-to quantization noise ratio in dB.

Explain the principle, block diagram and waveform of Adaptive Delta Modulator and discuss its advantages over conventional Delta Modulator.

Explain the working of a PCM system with block diagram and quantization error

Explain the PAM, PWM and PPM pulse modulation techniques with suitable waveforms/diagrams.

Numerical on PCM system to determine minimum sampling rate, number of bits, resolution and quantization error

Define Pulse Code Modulation (PCM) and discuss the quantization process and quantization error

A Pulse Code Modulation (PCM) system operates with quantization step size of $0.1 \text{V}$. If the signal being quantized has maximum amplitude of $2 \text{V}$, calculate the quantization error. Determine the signal to quantization noise ratio for the PCM system.

Differentiate between sampling theorems for low-pass and band-pass signals.

Explain Nyquist criterion and the condition to avoid aliasing in sampled signals.

Explain the generation/transmitter and demodulation/detection/receiver of QAM with block diagrams, including 8-QAM operation, constellation and comparison aspects.

Explain the concept, working, reliability advantage and receiver decoding of DPSK/DBPSK and how it differs from BPSK in terms of synchronization.

Draw the ASK, FSK and PSK waveforms for a given binary data sequence.

Describe BPSK modulation, derive its signal equation, explain its bandwidth, and explain coherent detection / working of BPSK transmitter and receiver with diagrams.

Numerical on QAM: given input data rate and carrier frequency, find baud rate and minimum double-sided Nyquist bandwidth/frequency.

Numerical problem on BPSK: given carrier frequency and bit rate, determine phase shift and calculate required bandwidth.

Explain the reasons for higher probability of errors in QPSK and minimum probability of error in offset QPSK.

Describe the concept of QAM and explain how it combines amplitude and phase modulation.

Compare bandwidth requirements of binary ASK, FSK and PSK and explain generation and recovery methods of ASK, FSK and PSK signals.

Calculate the maximum data rate for QPSK with given roll-off factor and transponder bandwidth.

Determine the bit interval for binary FSK with given mark and space frequencies.

Explain FSK modulation and describe the spectrum and bandwidth of FSK.

Define information and entropy. Calculate the channel capacity of a channel with 3 kHz bandwidth and SNR of 30 dB using the Shannon-Hartley theorem.

Write short notes on frequency translation and FDM?