Analog Communication (EC-403) - Important Questions

Determine the Fourier transform of standard signals: unit impulse, unit step, signum, sine and cosine functions.

What is the Gate function and what is its Fourier transform?

Explain what modulation is and why it is needed, including its main advantages, with a block diagram of a communication system.

Derive the time-domain expression for an AM wave (and its frequency spectrum).

Compare / differentiate AM, DSB-SC and SSB-SC modulation techniques including waveforms.

Explain generation of SSB-SC signal, including phase discrimination method, with diagram.

Draw the block/circuit diagram of Foster-Seeley (phase-shift) discriminator and explain its working for FM detection.

Explain detection/demodulation of FM signals using PLL.

What is significance of pre-emphasis and de-emphasis? Explain with neat sketch.

A 100 MHz carrier is frequency modulated by a sinusoidal signal of amplitude 20 V and frequency 100 kHz. If the frequency sensitivity of modulator is 25 kHz/Volt, determine modulation index, frequency deviation and Carson's bandwidth.

Draw the block diagram of a superheterodyne receiver and explain its operation / function of each block.

Explain the TRF (tuned radio frequency) receiver with block diagram and discuss its limitations / advantages and disadvantages.

Derive the figure of merit for DSB-SC modulation including noise performance.

Define / explain noise figure, noise temperature, and noise bandwidth (including noise figure measurement).

Write short notes on: i) Properties of impulse function ii) Convolution theorem in time and frequency domains iii) Auto-correlation, cross-correlation and power spectral density iv) Time scaling property of Fourier transform.