Antennas & Wave Propagation B.Tech Question Paper : vardhaman.org

College : Vardhaman College Of Engineering
Degree : B.Tech
Department : Electronics & Communication Engineering
Semester : V
Subject : Antennas & Wave Propagation
Document type : Question Paper
Website : vardhaman.org

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Antennas & Wave Propagation Question Paper :

Four Year B. Tech V Semester Supplementary Examinations June – 2014
(Regulations: VCE-R11)
(Electronics and Communication Engineering)
Date: 21 June, 2014 FN
Time: 3 hours
Max Marks: 75
Answer ONE question from each Unit

Related : Vardhaman College Of Engineering Analog Communications B.Tech Question Paper : www.pdfquestion.in/6376.html

Unit – I :
All parts of the question must be answered in one place only :
1. a) Define:
i. Radiation Intensity
ii. Directivity
iii. Gain
iv. HPBW
v. Effective Area of an antenna and write the corresponding mathematical expressions. 10M

b) Two lossless polarization matched antennas aligned for maximum radiation between them, are separated by a distance of 50? . The antennas are matched to their transmission lines and have directivities of 20dB. If the power at the input terminal of he transmit antenna is 10W, calculate the power at the receiver antenna terminal. 5M

2. a) Derive the expression for FRIIS formula. 6M
b) Find the directivity for the following intensity patterns:
i. Unidirectional cosine pattern U=Um Cos?
ii. Bidirectional cosine pattern U= Um Cos?
iii. Bidirectional sine pattern U= Um Sin? 9M

Unit – II :
3. a) Derive the expressions for the far field components for a small loop antenna. 6M
b) Show that the radiation resistance of a small loop antenna is Rr=31171(A/?2)2 9M
4. a) Given a linear uniform array of 16 elements with a separation of ? / 4between the elements. Compare the directivity of the array if the array is:
i. Broadside array
ii. Ordinary end fire array 6M
b) For any array of 2 isotropic antennas, show that the patterns are identical 9M

Unit – III :
5. a) Explain the practical design considerations for the monofilar axial –mode helical antenna? 10M
b) With a neat diagram, explain the helix structure? 5M
6. a) Explain the different antennas having essentially a single travelling wave? 10M
b) Explain the operation of V antenna in detail? 5M

Unit – IV :
7. a) Discuss the method adopted to obtain optimum flare angles of a pyramidal horn and the conditions on horn length to realize such a horn. 5M
b) Determine the length L, H-plane aperture and flare angles E ? and H ? of a pyramidal horn for which aE ? 10? . The horn is fed by a waveguide with 10 TE mode. Take 2 E ? ? ? and 0.375 H ? ? ? . Also calculate the beam widths and directivity. 10M

8. a) Write the advantages offered by dielectric lens antennas. 5M
b) How does a folded dipole differ from its standard version?.Show that a ? folded dipole offers a fourfold increase in its input impedance over that of a standard dipole. 10M

Unit – V :
9. a) Discuss the prominent modes of wave propagation and factors affecting them. 1 0 M
b) In an Ionospheric propagation, the angle of incidence made at a particular layer at a height of 200 km is 450 with a critical frequency of 6 MHz.Calculate the skip distance. 5M

10. a) Find the far field distance from an antenna with maximum dimension of 1m and operating frequency of 900 MHz. 5M
b) Define the terms surface and elevated ducts and duct gradient. Also discuss the duct propagation. 10M

B. Tech V Semester Regular Examinations, December – 2013 :
(Regulations: VCE-R11)
Antennas And Wave Propagation :
(Electronics and Communication Engineering)
Date : 14 December, 2013
Time : 3 Hours
Max. Marks : 75
Answer ONE question from each Unit
All Questions Carry Equal Marks

All parts of the question must be answered in one place only :
Unit – 1 :
1. a) Define
i. Isotropic and Directional Antenna
ii. Radiation Pattern
iii. Near and Far Fields
iv. Polarization of an antenna
v. Directivity of an antenna 10M

b) An antenna has a radiation resistance of 72O, loss resistance o 8O and power gain of 12dB. Determine the antenna efficiency and it’s directivity. 5M

2. a) Obtain the expressions for radiation resistance, maximum directivity and effective aperture assuming the expression for average power density for an infinitesimal dipole . 7M
b) Discuss the far field conditions for an antenna of length L and assuming far field conditions, calculate the amplitude and phase errors for an antenna of length 6l when observations are made at a distance of80l . 8M

Unit – 2 :
3. a) Show that the radiation resistance of a small loop antenna is Rr=31171(A/?2)2. 9M
b) Explain briefly the following:
i. Broadside array
ii. End fire array
iii. Scanning array 6M

4. a) Given a linear uniform array of 16 elements with a separation of l / 4 between the elements. Compare the directivity of the array if the array is
(i) Broadside array
(ii) Ordinary end fire array. 6M

b) Assuming the array factor for an uniform planar array, find the progressive phase shift between the elements in the x and y directions for a desired beam at and the conditions for principal maxima and grating lobes to occur. 9M

Unit – 3 :
5. a) What are the advantages and drawbacks of rhombic antenna? Design an alignment type rhombic antenna for an elevation angle to be operated at l = 3cm. 7M
b) Explain the principle of operation of V-dipole antennas. Design a V-dipole antenna to be operated at 20MHz with directivity of 7.5 dB. 8M

Unit – 4 :
7. a) Discuss the method adopted to obtain optimum flare angles of a pyramidal horn and the conditions on horn length to realize such a horn. 9M
b) Explain briefly the parameters affecting the performance of a parabolic reflector antenna. 6M

8. a) Write the advantages offered by dielectric lens antennas. 7M
b) Design a rectangular patch antenna on a dielectric substrate with to be operated at 3GHz.Determine the antenna parameters, bandwidth and VSWR, if the antenna is fed by a transmission line of 100O. Assume the thickness of the substrate as 2% of ?. 8M