JNTU
JNTU B.Tech III ANTENNAS AND WAVE PROPAGATION Previous Question Paper (May - 2019 - R16)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
Answer all questions. Each question carries marks as indicated.
Define Beam area and how does it related with Directivity of the antenna.
Answer
The Beam area (or beam solid angle) ΩA is the integral of the normalized power pattern over a sphere of 4π steradians. It is related to Directivity (D) by the inverse relationship:
Find the gain of a parabolic antenna with a 6 meters diameter dish and dipole feed at a frequency of 10GHz.
Answer
Given: Diameter D = 6 m, Frequency f = 10 GHz (λ = c/f = 0.03 m). The gain G of a parabolic antenna is given by G = η(πD/λ)2. Assuming an aperture efficiency η ≈ 0.6:
In decibels, GdB = 10 log10(236,870) ≈ 53.74 dBi.
List the applications of horn antennas.
Answer
Sign in to view the complete answer paper.
How is a folded dipole used in an antenna designed for TV reception?
Answer
Sign in to view the complete answer paper.
What are the advantages of microstrip antennas?
Answer
Sign in to view the complete answer paper.
What is offset feeding of parabolic reflector antenna?
Answer
Sign in to view the complete answer paper.
Differentiate Linear and Binomial arrays.
Answer
Sign in to view the complete answer paper.
Find the HPBW of a uniform linear array consisting of 16 isotropic point sources with spacing λ/4 and phase difference δ = -90°.
Answer
Sign in to view the complete answer paper.
Define optimum usable frequency of an ionospheric layer.
Answer
Sign in to view the complete answer paper.
What is multi-hop propagation?
Answer
Sign in to view the complete answer paper.
Part B
Define the half-power beam width and directivity of an antenna. And derive the relation between them.
Answer
Sign in to view the complete answer paper.
The far field of an antenna along the (θ,φ) direction is given by Eθ(θ,φ) = E0 cos²θ and Eφ(θ,φ) = 0. Calculate the maximum directivity of the antenna.
Answer
Sign in to view the complete answer paper.
Derive the field components and radiation resistance of a half wave dipole.
Answer
Sign in to view the complete answer paper.
Explain the Radiation characteristics of a pyramidal horn antenna with neat diagrams.
Answer
Sign in to view the complete answer paper.
Design an End-fire circularly polarized helix having HPBW of 45° and a circumference of 60cm at a frequency of 500MHz. Determine the turns needed, directivity and axial ratio.
Answer
Sign in to view the complete answer paper.
Explain the impedance transformation characteristics of a folded dipole.
Answer
Sign in to view the complete answer paper.
Sketch and explain the construction, operation of a helical antenna.
Answer
Sign in to view the complete answer paper.
Explain the characteristics of an active corner reflector with the help of image principle.
Answer
Sign in to view the complete answer paper.
Illustrate the geometrical features of parabolic reflectors.
Answer
Sign in to view the complete answer paper.
Draw the radiation characteristics of rectangular microstrip antenna.
Answer
Sign in to view the complete answer paper.
Calculate the FNBW of a 2.5 m parabolic reflector used at 6GHz. What will be its gain in decibels?
Answer
Sign in to view the complete answer paper.
Derive the expression for array factor of a linear broadside array of n isotropic elements.
Answer
Sign in to view the complete answer paper.
Find the array factor and plot the normalized radiation pattern of a broadside array of 5 isotropic radiators of spacing λ/2.
Answer
Sign in to view the complete answer paper.
Explain the 3-antenna method of measurement of the gain of a horn antenna with necessary relations.
Answer
Sign in to view the complete answer paper.
List different sources of errors in antenna measurements.
Answer
Sign in to view the complete answer paper.
Discuss the salient features of sky wave propagation. Bring out the various problems associated with this mode of propagation.
Answer
Sign in to view the complete answer paper.
Write short notes on D-layer and sporadic-E layer.
Answer
Sign in to view the complete answer paper.
Find the relation between Maximum usable frequency and Skip distance.
Answer
Sign in to view the complete answer paper.
Calculate the maximum usable frequency for a high frequency radio link between two points at a distance of 2500km on the surface of earth. Consider the height of ionosphere is 200km and the critical frequency is 5MHz.
Answer
Sign in to view the complete answer paper.