Shri Vishnu Engineering College for Women :: Bhimavaram Department of Electronics & Communication Engineering Antennas & wave Propagation

ASSIGNMENT-I 1. Define the terms: i. Antenna Aperture ii. Beam Width iii. Aperture Efficiency iv. Bandwidth. 2. a) Define the terms Radiation intensity, Gain, Resolution and Beam efficiency

b) The field pattern of an antenna is given by i) Plot the normalized power pattern. ii) Estimate the main beam efficiency of the antenna. 3. As related to antennas, define and explain the following terms: i ) Radiation Resistance ii) Effective Area iii) Effective Length iv) Efficiency 4. Find the effective aperture of an isotropic antenna operating at a wavelength of 10-2 m, deriving its directivity. 5. An antenna has a field pattern given Find the following: i) HPBW ii) Beam Width between first nulls (FNBW) 6. Find the effective length of a λ/2 dipole and λ/4 monopole. Hence calculate their directivities, using the appropriate radiation resistances. 7. Establish the relations between directivity and effective area, directivity and effective length. 8. An antenna has a radiation resistance of 63 ohms and a lossy resistance of 6Ω . If the power gain is 30, calculate the directivity and the efficiency of the antenna

ASSIGNMENT-II 1. a) State the Reciprocity Theorem for antennas? Prove that the Self Impedance of an antenna in transmitting and receiving mode is same. b) Define directivity, obtain the directivity of an isotropic antenna, short dipole and Half-wave Dipole 2. a) Give the expression for electric field due to current element. Find the distance from a radiating element such that Radiation and Induction fields are equal with necessary assumptions. b) What is short magnetic Di-pole? How is it realized? 3. a) Define the terms electrostatic field, induction field, and radiation field of an antenna and bring out their significance. b) Sketch and compare radiation patterns of horizontal half wave dipole with those of vertical half wave dipole c) What are short antennas 4. Explain how loop aerial is used for direction finding? Derive the relevant expression for electric field intensity for loop aerial. 5. Derive an expression for radiation resistance of half wave length slot aerial using babinet’s principle. Sketch the field pattern 6. . (a) Explain the terms Isotropic, Directional and Omni directional patterns. (b) Show that the radiation resistance of a λ/4 monopole is 36.5ohms. (c) Plot the radiation pattern of dipole antenna for 4 different dimensions in terms of wavelengths 7. . (a)What is radiation resistance of an antenna. (b)Show that the radiation resistance of half wave dipole is 73ohm 8. Distinguish between Dipole and Monopole

ASSIGNMENT-III

1. What is Array Factor? Find the array factor of 2 element array. 2. For an array of 2 identical infinitesimal dipoles oriented with a separation of ‘D’ and phase excitation difference ‘β’ between the elements. Find the angles of observation where the nulls of the array occur. The magnitude of excitation of the elements is same 3. A linear broadside array consist of 4 identical equal in phase point source with λ/3 spacing. Calculate and plot the field pattern. Also find the directivityand beam width. 4. What is optimum spacing used in parasitic array? Why. 5. Compare the performance of Broadside and End fire array. 6. Show that the width of principle lobe of an end fine array is greater than that of broadside array of the same length. 7 (a) Compare the radiation characteristics of uniform linear arrays, fed with i. uniform amplitudes. ii. Triangular taper amplitudes. iii. Binomially tapered amplitudes. (b) Mention the advantages and disadvantages of Binomial array. 8. a) How a unidirectional pattern is obtained in an end fire array. Explain? b) What are the advantages and disadvantages of binomial array?

ASSIGNMENT-IV 1. a) Sketch and explain the constructional features of Helical Antenna. b) Sketch and explain the basic set up for V-antenna and plot the pattern 2. a) Explain the need and the configuration of a Folded Dipole Antenna. Sketch its radiation pattern and compare its characteristics with those of simple λ/2 dipole. b) List out the design relations associated with a Rhombic Antenna. What are its applications? 3. a) List out the relations associated with a rhombic antenna. What are its applications? b) Discuss the merits and demerits of travelling wave antenna

4. (a) State the advantages and disadvantages of Rhombic Antenna. (b) Draw the radiation pattern for traveling wave antenna for L=_λ/2, λ, 2 λ, 4λ. 5. If a Helical antenna has spacing between turns 0.05m, diameter 0.1m, no. of turns equal to 20 and operates at 1000MHz. Find the null to null beam width of the main beam and also half power beam width and directivity. 6. Discuss the basic properties of Helical Antennas 7. Describe the construction and properties of Rhombic Antenna. 8. Describe the characteristics of long wire traveling wave antenna. Sketch their Pattern for lengths of i. λ/2 ii. 5λ iii. 20λ

ASSIGNMENT-V

1. (a) What is a parabolic element. How does a parasitic element act when length is greater than and smaller than λ/2. (b) Distinguish between Spherical and Cylindrical paraboloids. Comment on their aperture efficiency and applications 2. a) Explain all the structural requirements of a 5 element yagi antenna at 475MHz accounting for typical spacing, length to diameter ratios and input impedance Zn. (b) Explain the geometry, requirements and properties of parabolic reflectors. 3 A paraboloids operating at 5GHz, has a radiation pattern with null to null beam width of 100. Find the mouth diameter of the paraboloid, HPBW and power gain. 4. Draw the Yadi-Uda antenna and sketch its radiation, Write down the design equations of yagi-uda antenna. 5. (a) Describe the following reflectors : i. Truncated Paraboloids ii. Offset Paraboloids. (b) Find the gain, BWFN, HPBW of a paraboloids of 2m diameter operating at 5GHz when half wave dipole is used. 6. Derive an expression for the gain of a 900 corner reflector. 7. Explain the principle and working of Yagi Antenna

8. a) Design Yagi Uda antenna of six elements to provide a gain of 12dB if the operating frequency is 200MHz b) Explain with suitable sketches perpendicular mode of radiation in helical antenna.

ASSIGNMENT-VI 1. What is the principle of equality of path length? How is it applicable to horn antenna? 2. Obtain an expression for the directivity of pyramidal horn in terms of its aperture Dimensions. 3 Briefly explain the impedance measurement of a horn antenna by using slotted Line Method. 4. (a)Distinguish between sectoral, pyramidal and conical horns, with neat sketches. List out their utility and applications. b) With neat set up, explain the absolute method of measuring the gain of an antenna. 5 Describe the methods for measuring the below parameters for an antenna a) Gain b) Directivity with a neat block diagram [8+8] 6. a) What is Zoning? What are its advantages? b) Discuss the applications of Horn Antenna. Sketch the sectoral horns. 7. (a) Derive an expression for directivity of pyramidal horn in terms of aperture Dimensions (b) Explain the 3 antenna method of measurement of the gain of a horn antenna with necessary relations. 8. (a) Given that radiation pattern of an antenna are measured, explain how the directivity and power gain can be evaluated. (b) Distinguish between different types of lens antennas, explaining their curvature profiles. 9 (a) Explain why the beam widths in the two perpendicular planes of radiation of a square pyramidal horn will be different. Derive gain formula. (b) What is an antenna test range? What is minimum distance at which test should be taken for an antenna 5m in diameter and working at 6GHz? Derive the necessary expression.

ASSIGNMENT-VII 1. a) Explain the effects of D-layer in sky wave propagation. b) Distinguish between the terms MUF, LUHF and Optimum frequency. 2. a) Write short notes on i) Ionosphere abnormalities ii) Optimum working frequency and LUHF 3. Describe the fading of short wave broadcast signals 4. a) Write short notes on “Ground wave propagation and effective of earth” b) In case of ionosphere, explain D, E&F layers. 5. a) Explain the following: i) Ground Wave ii) Space Wave iii) Surface Wave b) Discuss the characteristics of ionospheric layer 6. (a) What is Virtual Height? Derive the expression for the same. (b) What is Skip Distance? Explain briefly 7. (a) Discus the salient features of Sky wave propagation (b) Bring out the various problems associated with this mode of propagation. How are these problems overcome? 8 (a) Show that MUF of ionized layer is given by fcp1+(D/2h)2 for flat earth. (b) Discuss the following: i. Ionospheric Storms. ii. Sudden Ionospheric Disturbances

ASSIGNMENT-VIII 1 a) Establish the relations for the received field strength of LOS propagated wave at i) Small distance ii) Large distance b) Describe the salient features of multi hop propagation 2. a) What is LOS propagation? Under what conditions it can exist? b) Explain the formation of inversion layer in the troposphere in the phenomenon of duct propagation

3 a) Discuss Duct Propagation dwell on causes and effects. b) Explain the bending of signals due to earths curvature. How is it useful for propagation 4. A communication link is to be established between two stations using half wave-length antenna for maximum directive gain. Transmitter power is 1 KW, frequency of operation is 100 MHz and distance between transmitter and receiver is 100 Km. what is the maximum power received by receiver? Explain and derive the formulas used 5. (a) Describe the troposphere and explain how tropospheric ducts can be used for microwave propagation. (b) Derive the expression for space wave electric field produced by an antenna at a distance point, assuming a flat earth 6.(a) Space wave propagates between transmitting and receiving stations of heights ‘h1’ and ‘h2’ respectively. Derive the expression for field strength. (b) What are the different paths used for propagating radio waves from 300KHz and 300MHz 7. (a) Derive the field strength of tropo spheric wave (b) Give an account of effect of earths imperfections and roughness. 8. Discuss the effects of hills, building and other obstacles an space wave propagation