JNTU
JNTU B.Tech IV SATELLITE COMMUNICATIONS Previous Question Paper (July - 2021 - R16)
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Discuss the laws of planetary motion which apply to any two bodies in space that interact through gravitation.
Answer
Kepler's laws of planetary motion describe the orbital mechanics of two bodies interacting via gravity:
- First Law (Law of Ellipses): The orbit of each satellite is an ellipse with the center of mass of the system (the primary body, such as the Earth) at one of the two foci.
- Second Law (Law of Equal Areas): A line joining the satellite and the center of the Earth sweeps out equal areas in equal intervals of time. This implies that the satellite's orbital speed is highest at perigee and lowest at apogee.
- Third Law (Law of Harmonies): The square of the orbital period (T) is directly proportional to the cube of the semi-major axis (a) of the orbit. Mathematically, T2 = (4π2 / μ) * a3, where μ is the Earth's gravitational parameter.
Determine the look angles for the ground station antenna by necessary calculations.
Answer
Look angles, specifically the Azimuth (Az) and Elevation (El), define the pointing direction of a ground station antenna toward a satellite. Given the Earth's radius (Re), the satellite's orbital radius (r), and the ground station latitude (λ) and longitude (φ), the elevation angle is calculated as:
where β is the central angle between the ground station and the satellite sub-point. The azimuth angle is derived from:
These calculations ensure the antenna is correctly aligned with the satellite's position relative to the local horizon and true north.
Explain how satellite must have very high reliability in the hostile environment of outer space, and develop a strategy that must be devised that allows some components to fail without causing the entire communication capacity of the satellite to be lost.
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Explain the different methods to keep satellite stable and pointed in the desired direction to keep the antennas properly oriented towards earth.
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Prove that C/N ratio is directly proportional to G/T ratio from calculation of system noise temperature.
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A satellite TV signal occupies the full transponder bandwidth of 93MHz, and it must provide a C/N ratio of 62dB at the destination earth station. Given that the total transmission losses are 600dB and the destination of earth station G/T ratio is 81dB/K. Calculate the EIRP required.
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Discuss about the Antenna that is suitable for earth station by its characteristics.
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Explain about the different types of satellite tracking system with neat diagram.
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Discuss how GPS revolutionized navigation and position location in detail.
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Explain the design of any one Satellite Constellation with a neat diagram.
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An earth station is located at 400W longitude and 700N latitude. With respect to a geostationary satellite located at 600W longitude, find the earth station’s Azimuth and elevation angles by considering the orbital radius as 42163km and Earth’s radius as 6376km.
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Discuss about the orientation of satellite in space with respect to earth.
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Demonstrate the meaning of backoff and why is it necessary in multiple access system.
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Discuss about the amplifier that takes low power signals and enhances them greatly inorder to send the signal over a wire or from a dish.
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A TDMA system operates at 90M bits/s with a 4ms frame time. Assume that all slots are of equal length and guard time 2 micro sec is required between slots. Compute the efficiency of the communication resource for the case of 1, 5, 2, 07 slots per frame.
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What is meant by distance-insensitive communication system? Also discuss the advantages of satellite communication.
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