Electronic and Communication — Summer 2025

Define the following terms:

Energy Signal, ii) Power Signal, iii) Parseval’s theorem for energy signal

What is modulation and why modulation is required in communication?

What are the natural sources of noise? Explain Shot noise, Partition noise and Thermal noise.

Define the following terms:

Noise Factor, ii) PSD of White Noise iii) Signal to Noise Ratio

Explain the Skin effect.

Amodulating signal m(t) = 10cos⁡(2𝜋×103t) is amplitude modulated with a carrier signal c(t) = 50cos⁡(2𝜋×105t). Find the modulation index, the carrier power, and the power required for transmitting AM wave.

Explain Amplitude Modulation with required waveforms. Derive the mathematical equation for an Amplitude modulated wave.

State and prove time shifting property of Fourier transform.

An amplifier with 10 dB noise figure and 3 dB power gain is cascaded with a second amplifier which has a 10 dB power gain. What is the overall noise figure?

What are the different methods for generation of SSB signals? Explain SSB generation by phase shift method with necessary block diagram and derivations

State and prove Time-scaling property of Fourier transform.

Two resistors 20 KΩ and 50 KΩ are at room temperature (290K) for a bandwidth of 100KHz. Calculate thermal noise (i) for each resistor (ii) for two resistors in series (iii) for two resistors in parallel

With help of neat diagram describe the working of a super heterodyne receiver.

Compare DSB-FC and SSB –SC modulation schemes and prove that use of SSB technology is preferable as compared to use of DSB technology.

Find the Fourier Transform of following function: 𝜏 𝜏 t 1⁡⁡⁡⁡⁡⁡⁡⁡for− < x(t) = rect( ) = { 2 𝜏 0⁡⁡⁡⁡⁡⁡⁡⁡⁡⁡otℎerwise

Enlist various methods of FM generation. Explain any one of them.

What is VSB what is its significance?

Give a comparison between Series Tuned and Parallel Tuned circuits.

An FM wave is given by x(t) = 20sin⁡(6×108t+7sin1250t). Determine:

carrier frequency1 ii) modulating frequency iii) modulation index and iv) maximum deviation

Define the following terms related with radio receiver:

selectivity (ii) fidelity (iii) sensitivity

Explain the importance of pre-emphasis and de-emphasis circuits.

Describe the technology behind Ham Radio and discuss its importance during natural calamities.

Define Image Frequency. An AM broadcast receiver has an IF of 465 kHz and is tuned to 1000 kHz and the RF stage has one tuned circuit with a Qof 50. Calculate the image frequency.

With the help of neat diagram and waveform explain the operation of an envelope detector.

List all the basic FM demodulators. Draw and explain Foster Seeley Discriminator in detail.