JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III PRINCIPLES OF ELECTRONIC COMMUNICATIONS Previous Question Paper (October - 2020 - R16)
Answer any five questions. All questions carry equal marks.
Main
A communication system has five stages, with gains of 12, 245, 68, 231, and 9 dB. What is the overall gain?
Answer
To calculate the overall gain of a multi-stage communication system where individual gains are expressed in decibels (dB), the total gain is simply the sum of the individual gains:
Given the individual gains as 12 dB, 245 dB, 68 dB, 231 dB, and 9 dB, the calculation is:
The overall gain of the communication system is 565 dB.
Explain the frequency range and applications of UHF, SHF and EHF.
Answer
The radio frequency spectrum is categorized into various bands based on frequency ranges, each serving distinct communication purposes:
- Ultra High Frequency (UHF): This band covers the frequency range from 300 MHz to 3 GHz. It is primarily used for television broadcasting, mobile communication (GSM/LTE), Wi-Fi, Bluetooth, and GPS systems. UHF signals are characterized by line-of-sight propagation and are capable of penetrating buildings effectively.
- Super High Frequency (SHF): This band spans from 3 GHz to 30 GHz. It is widely utilized for satellite communication, microwave links, radar systems, and high-speed wireless local area networks (WLAN). Due to the high frequency, these waves exhibit highly directional propagation, making them suitable for point-to-point communication.
- Extremely High Frequency (EHF): This band ranges from 30 GHz to 300 GHz. It is employed in advanced applications such as radio astronomy, remote sensing, high-resolution radar, and 5G millimeter-wave (mmWave) communications. EHF signals provide very high bandwidth but are susceptible to atmospheric attenuation, particularly due to rain and oxygen absorption.
A power amplifier has an input of 90 mV across 10 kΩ. The output is 7.8 V across an 8-Ω speaker. What is the power gain, in decibels? You must compute the input and output power levels first.
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A signal travels a distance of 75 ft in the time it takes to complete 1 cycle. What is its frequency?
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A television signal occupies a 6-MHz bandwidth. If the low-frequency limit of channel 2 is 54 MHz, what is the upper-frequency limit?
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Determine the modulation index and bandwidth for FM and PM signals for a modulating signal
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Compare PAM with PWM.
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Draw the QPSK transmitter and explain each block.
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Discuss the oversampling and under sampling operating and state their advantages and disadvantages.
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Discuss the Signal flow in a VoIP system.
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Illustrate the diagrams of LANs arranged according to the three basic topologies: star, ring, and bus.
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Explain the paging systems.
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An office with 20 PCs is to be wired so that any computer can communicate with any other. How many interconnecting wires (or links, L) are needed?
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Discuss the Ethernet frame format.
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Explain two types of optical transmitter components and their main operating characteristics.
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Discuss the advantages and disadvantages of satellite communications.
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Detail notes about GSM – system overview, physical and logical channels.
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Explain why IEEE 802.16 is a MAN technology.
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