S.R.M. Institute of Science & Technology Deemed University School of Electronics & Communication Engineering

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1 S.R.M. Institute of Science & Technology Deemed University School of Electronics & Communication Engineering Question Bank Subject Code : EC401 Subject Name : Antennas and Wave Propagation Year & Sem : IV Year B.Tech (ECE),7th Sem. UNIT-I PART-A 1. Define Isotropic radiator. 2. Calculate the directivity of an Isotropic antenna. 3. Differentiate Radian & Steradian. 4. Define Gain & Beam width of an antenna. 5. Derive an expression for effective aperture area of antenna. 6. Calculate the maximum effective aperture area of antenna which is operating at a wavelength of 2 meters and has a directivity of Define Antenna Efficiency. 8. Write note on radiation pattern. 9. What is radiation intensity and explain in terms of poynting vector? 10. Explain directivity of an antenna. 11. Find out the radiation resistance of a?/16 wire dipole in free space. 12. Define power gain and write down the relation between directive gain and power gain. 13. Define radiation resistance and write down the expression for it. 14. Differentiate antenna bandwidth and beam width. 15. Define beam solid angle and antenna beam efficiency. 16. An antenna has a radiation resistance of 72 Ohms, a loss resistance of 8 Ohms and a power gain of 12dB. Determine the antenna efficiency and its directivity. 17. Define Terminal impedance. 18. State reciprocity theorem and briefly explain it. 19. Calculate the radiation resistance of short dipole. 20. Calculate a maximum effective aperture of a half wave dipole. 21. Calculate the length of a half wave dipole antenna meant to have correct half wave length at 60 MHz. 22. Calculate the maximum effective aperture of a microwave antenna which has a directivity of Calculate the radiation resistance of an antenna which is drawing 15A current and radiating 5 KW. 24. Calculate the power being radiate by an antenna having a radiation resistance of 50 Ohms and is drawing a current of 8A. 25. Calculate the radiation resistance of an antenna which is radiating 1000W and drawing current of 5A. 26. How much current does an antenna draw when radiating 1000W and is having a radiation resistance of 300 Ohms.

2 27. Mention the radiation and Induction field component for a small current element. 28. Show the directivity of an electric current element 3/ Define poynting vector. 30. What is effectiveness ratio? 31. What is scattering loss aperture? 32. Define effective length of an antenna. PART - B 1. Explain the retarded vector potential in detail. 2. Derive an expression for the power radiated by the current element and calculate the radiation resistance. 3. Derive an expression for the far field component of a half wave dipole of an antenna. 4. a) Derive the total power radiated by half wave dipole. b) Show that the radiation resistance of a half wave dipole is 80?2 (dl/?)2 Ohms. 5. Explain the reciprocity theorem in detail. 6. Derive an expression for the electric field and magnetic field due to a current element at a distance point in free space. 7. a) Derive an expression for the gain of half wave dipole. b) Explain effective aperture area with its types in detail. 8. At what distance in?, is the radiation component of magnetic field twice the inductance component? At what distance is it 100 times. UNIT II Antenna Arrays PART - A 1. What is an array and mention the various forms of antenna arrays? 2. What is a uniform linear array? 3. What is Broad side array and draw its radiation pattern? 4. What is End fire array and draw its radiation pattern? 5. What is collinear array? 6. What is parasitic array? 7. What is pattern multiplication concept? 8. List some of the advantages of pattern multiplication. 9. What is tapering of array? 10. Write a note on Binomial array. 11. How the secondary lobes are eliminated? 12. What is Pascal s triangle? 13. What is a Phased array? 14. What is a smart antenna? PART-B 1. Write short notes on various forms of arrays i.broad side array ii.end fire array iii.collinear array iv.parasitic array

3 2. Derive the expression for the far field pattern of an array of 2 isotropic point sources i) Equal amplitude and phase ii) Equal amplitude and opposite phase iii) Unequal amplitude and any phase 3. Explain the principle of Pattern multiplication. 4. Explain the array of N- sources of equal amplitude and spacing- Broad side case i. Direction of pattern maxima ii. Direction of pattern minima ii. Beam width of major lobe 5. Explain the array of N- sources of equal amplitude and spacing- End fire case i) Direction of pattern maxima ii. Direction of pattern minima ii) Beam width of major lobe 6. Write short notes on i. Binomial arrays ii. Phased arrays UNIT-III - SPECIAL PURPOSE ANTENNAS PART-A 1. What are the applications of loop antenna? 2. Give the reason for poor radiation of a loop antenna. 3. Distinguish between sectorial and pyramidal Horn antenna. 4. What are the advantages of folded dipole? 5. What is a folded dipole? What are its important properties? 6. Draw the structure of Log- periodic antenna. 7. What is a Yagi Uda array? 8. State Babinet s principle. 9. Why is flaring required in Horn antennas? 10. What is primary radiation and secondary radiation as applicable to parabolic reflector? 11. What is the reason for using Yagi antenna for TV broadcast reception? 12. What are the applications of Yagi Uda antenna? 13. What are parasitic elements and where are they used? 14. How does a parabolic reflector provide very high gain? 15. What is a parasitic element? How does it act when length is greater than and smaller than? / 2? 16. What is cheese feed as applicable to parabolic reflectors? 17. Mention the antennas used in medium frequency range. 18. How is a high frequency dipole antenna fed and matched with driving source? 19. Sketch the diagrams of various types of Horn antennas. 20. What are Traveling wave antennas? 21. Distinguish between resonant antenna and TWA? 22. Distinguish between standing wave antenna and TWA?

4 23. Define Spill over. 24. What is meant by smart antenna? 25. What is the principle of microwave antenna? 26. Define pitch angle. When a = 0o and a = 90o, how does the helical antenna behave? 27. What are the parameters to be considered in the design of an helical antenna? 28. What are the different modes of operation that can be used in Helical antenna? 29. List the applications of Helical antenna. 30. Why does the normal mode of operation is not preferred in Helical antenna? 31. Draw the structure of an Helical antenna with its parameters. 32. What is Cassegrain feed mechanism? PART - B 1. Explain the principle of traveling wave radiator. 2. Derive an expression for the radiated field due to a TWA. 3. Obtain the expression for the field produced by TWA and compare its radiation with resonant antenna. 4. Obtain the expression for the emf due to loop antenna and explain its use as a Direction finder. 5. Explain the special features of various types of Horn antennas and frequency independent antennas. 6. With a suitable diagram, discuss the construction and operation of a Yagi antenna. 7. Write detailed notes on (a) Parabolic reflectors (b) Log Periodic antennas 8. (a) Explain the principle of operation and applications of folded dipoles. (b) With a suitable diagram explain the construction and principle of operation of a log periodic antenna. 9. Write short notes on (a) Slot radiators (b) Loop antennas 10. How does a log periodic antenna provide a large bandwidth of operation? 11. Explain the principle of operation and applications of loop antenna. 12. Write detailed notes on (a) Horn antennas (b) Frequency independent antennas. 13. Explain the principle of operation and applications of loop antenna. 14. Explain in detail the working principle of Helical antenna in (a) Normal mode (b) Axial mode 15. Explain in detail the design aspects of Microstip antenna. UNIT-IV Radio Wave Propagation PART-A 1. What are the various modes of Propagation? 2. What is Duct Propagation 3. What do you mean by ground Wave Propagation 4. What do you mean by Sky Wave Propagation 5. What do you mean by Space Wave Propagation 6. What do you mean by Troposphere Scatter Propagation 7. Write short notes on Structure of Troposphere 8. Write short notes on Structure of Ionosphere layers 9. Write short notes on D region 10. Write short notes on Normal E region

5 11. Write short notes on Sporadic E region 12. Write short notes on F region 13. What is Critical Frequency 14. What is Magneto Ionic Splitting? 15. Define Gyro Frequency 16. Define Virtual Height 17. Define Maximum Usable Frequency(MUF) 18. Define Skip Distance 19. Define Optimum Working Frequency(OWF) 20. State some Ionospheric abnormalities 21. Define Sun Spot Cycle 22. Define Fading and Mention its types 23. What are Whistlers 24. What do you understand by Multi hop Propagation? 25. Write the ranges for various layers of atmosphere. PART-B 1. Explain briefly the various modes of Propagation 2. Explain Ground Wave Propagation in detail 3. Explain the Structure of Atmosphere 4. Explain the various layers of Ionosphere 5. Explain the effect of Earth s Magnetic Field on Radio wave Propagation 6. Explain Virtual Height and derive the Expression 7. Explain Maximum Usable Frequency and show how to Calculate MUF 8. Explain (a) Skip Distance (b) Optimum Working Frequency 9. Explain briefly about Ionospheric abnormalities 10. Determine the Effective Earth s Radius in Space Wave Propagation 11. Explain Super Refraction. UNIT V - ANTENNA MEASUREMENTS PART A 1. What are the types of antenna measurements? 2. Define Impedance measurements. 3. Define Pattern measurements. 4. Define Gain of antenna. 5. Define Radiation Resistance. 6. Define Transmission bandwidth of an antenna. 7. Define Power Gain. 8. Define VSWR. 9. What is standing wave ratio method of impedance measurements? 10. Define Radiation pattern measurements. 11. Define Directivity. 12. Define antenna Radiation Efficiency.

6 13. Define Polarization measurement. 14. Define Antenna Aperture Efficiency. 15. List the different methods used for measuring the Polarization. 16. Define Vertical Incidence measurement. 17. Define Oblique incidence measurement. 18. Give the relation between Vertical and Oblique incidence transmission. 19. Determine the gain and beam width for a parabolic antenna with 10M-diameter dish and dipole feed at 10GHz. 20. Define Beam width of antenna. PART B 1. Describe the methods for measuring the gain and beam width of antenna. 2. Describe the methods for measuring the Power gain, Radiation efficiency and Transmission bandwidth of an antenna. 3. Describe the Slotted line technique for Impedance measurement. 4. Describe how the radiation pattern and Radiation resistance of a given antenna can be measured experimentally. 5. Derive the relation between oblique and vertical incidence transmission. 6. Write short notes on Vertical incidence measurement of the ionosphere. 7. Write short notes on Oblique incidence measurement of the ionosphere. 8. Describe briefly about Polarization measurements. 9. Derive an expression to determine Antenna efficiency and Antenna Aperture. 10. Derive an expression to determine the Directivity of an antenna.

1. What are the applications of loop antenna? (May2011) 2. Define Pattern Multiplication (May2011)

UNIT-II WIRE ANTENNAS AND ANTENNA ARRAYS 1. What are the applications of loop antenna? (May2011) 2. Define Pattern Multiplication (May2011) 3. A uniform linear array contains 50 isotropic radiation with