JNTU QUESTION BANK ANTENNAS AND WAVE PROPAGATION MODEL QUESTION PAPER PREVIOUS YEAR QUESTION PAPER FOR 3rd YEAR FIRST SEMESTER ECE.CEET BRANCHES
JNTU QUESTION BANK ANTENNAS AND WAVE PROPAGATION MODEL QUESTION PAPER PREVIOUS YEAR QUESTION PAPER FOR 3rd YEAR FIRST SEMESTER ECE.CEET BRANCHES
III B.Tech I Semester Supplimentary Examinations, February 2008
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) Explain the following terms:i. Beam Width
ii. Omni Directional pattern
iii. Side Lobe Level
iv. Radiation resistance
v. Field Pattern of antenna.
(b) Define the terms Directivity and Power Gain. Show that the Directivity of a
short current element is 1.5. [8+8]
2. (a) Starting from the fundamentals, derive an expression for radiated electric field
for half wave dipole and sketch the field strength pattern.
(b) Prove that leff(transmitting) is same as leff(receiving) for any antenna where
leff is effective length of an antenna. [8+8]
3. (a) How an unidirectional pattern is obtained in an end fire array? Explain in
detail.
(b) List out the mathematical relations for a N element half wavelength spaced
binomial array. Hence find the directivity, HPBW for N=20. [8+8]
4. (a) Explain how a rhombic Antenna is formed by a V antenna and an inverted V
Antenna.
(b) Explain the reason why length of a traveling wave radiation is multiple of half
wave length. [8+8]
5. (a) Discuss the application of the Image antenna concept to the 900 corner reflec-
tor.
(b) What is a parabolic cylinder antenna? Derive an expression for field distrib-
utions on the surface of reflector. [8+8]
6. (a) What is Zoning? What are its advantages?
(b) Discuss the applications of Horn Antenna. Sketch the sectoral horns. [8+8]
7. (a) Show that Ionosphere act as a variable refractive index medium.
(b) A radio link has to be established between two earth station at a distance of
25000kms. If the height of ionosphere is 200kms and its critical frequency is
5MHz. Calculate the MUF for the given path. Also calculate the electron
density in the ionosphere layer. [8+8]
8. (a) A police radio transmitter operating at a frequency 1.69GHz is required to
provide a ground wave having a strength of 0.5mv/m at a distance of 16km.
The transmitter antenna, having an efficiency of 50% produces a radiating
field proportional of cosθ. The ground wave has σ= 5 × 10−5 mho/cm and εr
= 15. Calculate the power transmitted.
(b) Derive the fundamental equation for free space propagation. [8+8]
III B.Tech I Semester Supplimentary Examinations, February 2008
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. Find the effective length of a λ/2 dipole and λ/4 monopole. Hence calculate theirdirectivities, using the appropriate radiation resistances. [16]
2. (a) Derive expressions for the electric and magnetic fields radiated by a half wave
length dipole antenna.
(b) A grounded vertical antenna has an effective height of 111.3 mts and operates
at a wavelength of 18.8kms,with base current of 725 amps, Find the E and H
fields at a distance of 150kms and power radiated by it. [8+8]
3. (a) What is the necessity of an Array? Explain the three different types of arrays
with regard to beam pointing direction.
(b) 64 isotropic elements are to be arranged in a binomial array form. Determine
the current ratios and find polar plot of the array. [8+8]
4. (a) Describe the construction and properties of Rhombic Antenna.
(b) Describe the characteristics of long wire traveling wave antenna. Sketch their
pattern for lengths of
i. λ/2
ii. 5 λ
iii. 20 λ. [10+6]
5. (a) With reference to paraboloids,explain the following:
i. Aperture Efficiency
ii. Front toBack Ratio
iii. Types of Feeds.
(b) Design Yagi-Uda antenna of six elements to provide a gain of 12dB if the
operating frequency is 200MHz. [8+8]
6. (a) What is the principle of equality of path length? How is it applicable to horn
antenna?
(b) Discuss how the directivity of horn antenna can be measured. [8+8]
7. (a) Show that Ionosphere act as a variable refractive index medium.
(b) A radio link has to be established between two earth station at a distance of
25000kms. If the height of ionosphere is 200kms and its critical frequency is
5MHz. Calculate the MUF for the given path. Also calculate the electron
density in the ionosphere layer. [8+8]
1 of 2
Code No: R05310403 Set No. 2
8. (a) Prove that the radio horizon distance between transmitting and receiving an-
tennas is given by dmiles=p2ht+p2hr.
(b) Write short notes on “Troposcatter”. [8+8]
III B.Tech I Semester Supplimentary Examinations, February 2008
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) As related to Antennas, define and explain the following terms:i. Directivity
ii. Radiation Resistance
iii. Beam Width
iv. Band Width.
(b) Evaluate the directivity of
i. An Isotropic Source
ii. Source with Bi-Directional cos θ power pattern. [8+8]
2. (a) What is Retarded Potential? Explain different approaches to solve radiation
Problems.
(b) Explain the Lorentz Gauge Condition and show that
∇ ∇. ¯A/jωµε-jω ¯A = 1 / jωµε (∇∗∇∗¯A)
where ¯A is magnetic vector potential. [8+8]
3. (a) Explain the principle of pattern multiplication.What is the effect of earth on
the radiation pattern of antennas.
(b) A uniform linear array consists of 16 isotropic point source with a spacing of
λ/4 if the phase difference α=-900. Find
i. HPBW.
ii. Directivity.
iii. Effective aperture. [8+8]
4. (a) Explain the construction and radiation characteristics of Helical Antenna.
(b) What is a ‘V’ antenna. Explain its characteristics. [8+8]
5. (a) Explain how the radiation pattern of folded dipole will be modified with the
addition of a reflector and two directors parasitic elements.
(b) Bring out the differences between Active and Passive Corner Reflectors. What
are Retro Reflectors? [8+8]
6. (a) Explain the principle of operation of Dielectric Lens Antenna.
(b) Write short notes on “Radiation from Sectoral Horn”. [8+8]
1 of 2
Code No: R05310403 Set No. 3
7. (a) What are different mechanisms of propagation of electromagnetic waves? Ex-
plain.
(b) What is Critical Frequency? What is Virtual Height? Find the maximum
distance that can be covered if the virtual height of the ionospheric layer is
250kms. [8+8]
8. (a) Write short notes on “M Curves and their characteristics”.
(b) Show that the radius of curvature of ray path is given by 2/(dεr/dh) for
tropospheric waves. [8+8]
III B.Tech I Semester Supplimentary Examinations, February 2008
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) Explain the terms “Isotropic”, “Directional” and “Omni directional pattern”,“Radiation Intensity”.
(b) Define Effective Aperture and calculate the effective aperture of a 0.25 λ di-
pole. [8+8]
2. (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. [8+8]
3. (a) What are the various differences between binomial and linear arrays.
(b) Design a 8 element broadside array of isotropic sources of λ/2 spacing between
elements. The pattern is to be optimum with a side lobe level 26db down the
mainlobe maximum. [8+8]
4. (a) Distinguish between
i. Resonant and Non Resonant antennas.
ii. Narrow Band and Wide Band antennas.
(b) Show that a single wire excited with a traveling wave current is an end fire
antenna with a sharp null along the direction of extension of the wire. [8+8]
5. (a) A Paraboloid reflector of 1.8m diameter is used at 6GHz. Calculate the beam
width between the nulls and gains in dBs.
(b) Design Yagi Uda antenna of six elements to provide a again of 12dB if the
operating frequency is 200MHz. [8+8]
6. (a) Distinguish between Sectoral, Pyramidal and Conical horns. Explain their
utility.
(b) With a neat setup, explain the absolute method of measuring the gain of an
antenna. [8+8]
7. (a) Describe the salient features of Ground wave propagation. Discuss the effect of
frequency earth constants and curvature of earth on ground wave propagation.
(b) Communication by ionosphere propagation is required for a distance of 200kms.
height of the layer is 220kms and the critical frequency is 5MHz. Find MUF.
[8+8]
8. (a) Write explanatory notes on
i. Selective fading and Interference fading.
ii. Field Strength calculation for radio AM broadcast waves.
(b) A communication link is to be established between two stations using half
length antenna for maximum distance gain. Transmitter power is 1KW, dis-
tance between transmitter and receiver is 100km. What is the maximum power
received by receiver? Frequency of operation is 100MHz. [8+8]
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