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- Antenna and wave Propagation - AWP
- 2018
- PYQ
**Biju Patnaik University of Technology Rourkela Odisha - BPUT**- Electronics and Communication Engineering
- B.Tech
**5135 Views**- 68 Offline Downloads
- Uploaded 1 year ago

Registration No : Total Number of Pages : 02 B.Tech. PET6J012 6th Semester Regular Examination 2017-18 ANTENNAS AND WAVE PROPAGATION BRANCH: ECE, ETC Time: 3 Hours Max Marks: 100 Q.CODE: C445 Answer Part-A which is compulsory and any four from Part-B. The figures in the right hand margin indicate marks. Q1 a) b) c) d) e) f) g) h) Part – A (Answer all the questions) Answer the following questions : multiple type or dash fill up type : Wave front is basically a locus of points acquiring similar _______ If the path difference of two waves with single source traveling by different paths to arrive at the same point, is λ/2, what would be the phase difference between them? a. β x (λ/2) b. β / (λ/2) c. β + (λ/2) d. β – (λ/2) The knowledge of which parameter is sufficient for deriving the time varying electromagnetic field? a. Electric field intensity b. Magnetic field intensity c. Current density d. Power density At which angles does the front to back ratio specify an antenna gain? a. 0° & 180° b. 90° & 180° c. 180° & 270° d. 180° & 360° Which among the following exhibits perpendicular nature in TEM wave? a. Electric field b. Magnetic field c. Direction of propagation d. All of the above If the magnetic field component of a plane wave in a lossless dielectric is H = 50 sin (2π x 106 t – 6x) azmA/m, what will be the wave velocity? a. 1.047 x 106 m/s b. 1.257 x 106 m/s c. 2.50 x 106 m/s d. 3 x 106 m/s Which conversion mechanism is performed by parabolic reflector antenna? a. Plane to spherical wave b. Spherical to plane wave c. Both a. and b. d. None of the above If the radius of loop is λ/ 20 in a free space medium, what will be the radiation resistance of 8-turn small circular loop? a. 0.7883 Ω b. 50.45 Ω c. 123.17 Ω d. 190.01 Ω (2 x 10)

i) j) Q2 a) b) c) d) e) f) g) h) i) j) Q3 a) b) Q4 a) b) Q5 a) b) Q6 a) b) Q7 a) b) Q8 a) b) Q9 a) b) If a linear uniform array consists of 9 isotropic elements separated by λ/4, what would be the directivity of a broadside array in dB? a. 6.53 dB b. 7.99 dB c. 8.55 dB d. 9.02 dB For avoiding ground losses, better is the surface conductivity, less is the __________. Answer the following questions : Short answer type : Define a Hertizian dipole. What is meant by retarded potential? Define effective area and specify its significance. What is the relationship between effective aperture and directivity? What are the advantages of antenna arrays? Define array factor. What are the features of pyramidal horn antenna? What are the limitations of lens antenna? What are the applications of log periodic and Yagi Uda antenna? What are the different methods of feeding slot antennas? Differentiate V antenna from rhombic antenna. Part – B (Answer any four questions) Derive the expression for power radiated by a current element and its radiation resistance. Deduce the field quantities and draw radiation pattern for a half wave dipole antenna. (2 x 10) (10) (5) For an array N element feed with signal of equivalent amplitude and phase, determine the maxima and minima directions. Draw the radiation pattern. What is folded dipole antenna? Explain the term pattern multiplication. (10) Obtain the expression for the field and the radiation pattern produced by a 2element array of infinitesimal dipole with distance of separation λ/2 & currents of equal magnitude and phase shift 180° Derive the expression for radiation resistance of small loop antenna. (10) Explain the principle of operation & application of parabolic reflector and its types of feeding. Two space crafts are separated by 3 km. Each has an antenna with directivity D = 200 operating at 2 GHz. If craft A’s receives 20 db power, what is the transmitter power by craft B? (10) Explain the geometry of a log periodic antenna. How wideband operation is possible with this antenna. Give the design equations. With necessary illustrations explain the radiation characteristics of Yagi Uda antenna. (10) Explain the following in details i. Baluns ii. Polarization mismatch Derive the expression for calculating field strength at a distance in space wave Propagation. (10) Explain the measurement procedure of the measurement of VSWR and radiation pattern. Explain the different types of Diversity technique. (10) (5) (5) (5) (5) (5) (5)

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