JNTU B.Tech III ANTENNAS AND WAVE PROPAGATION Previous Question Paper (November/December - 2018 - R13)

An antenna has a field pattern given by E(θ) = cos²θ for 0^o ≤ θ ≤ 90^o. Find the half power beam width.

Define any three antenna parameters.

What is folded dipole antenna?

Why is an electromagnetic horn antenna a well matched antenna?

What is Fermat’s principle?

List the advantages of Cassegrain feed.

Find the near and far field distances for a reflector antenna with diameter D = 0.5m at 300 GHz.

Draw the radiation pattern of an array of four isotropic elements spaced by λ/2.

What is impact of imperfect earth on surface wave?

Calculate the maximum distance at which signal from transmitting antenna with 144 m height would be received by the receiving antenna of 25m height.

Derive the Friis transmission equation and discuss the terms isotropic, omni-directional and principal patterns.

A short antenna with a uniform current distribution in free space has Idl = 3×10^-4 A-m. Calculate the far field E_θ component for θ = 90^o, Φ = 0^o, λ = 10 cm and r = 200 cm.

Derive the expression for power radiated and radiation resistance of alternating current element.

A 50cm long vertical dipole operating at 30MHz radiates a maximum electric field of 15 mV/m at 5 km distance. Find its power radiated, input current and maximum magnetic field at the same distance.

Explain the design considerations of Pyramidal Horns.

Sketch the geometry of a helical antenna, and explain the principle of working in normal mode.

How a Rhombic antenna has high directivity? Explain by means of its geometrical structure.

Draw the structure of helical antenna and explain its working in axial mode.

Compare different feeding methods that are associated with parabolic reflectors.

For a parabolic reflector of 7.5m diameter at 4 GHz, find the BWFN, HPBW, Directivity and effective aperture.

With neat schematic, describe the radiation characteristics of a rectangular microstrip patch antenna, using basic transmission line model.

Calculate and plot the pattern of an ideal square-corner reflector with λ/2 driven antenna spaced λ/2 from the corner but with the antenna displaced 20^o from the bisector of the corner angle. The pattern to be calculated is in a plane perpendicular to the antenna and to the reflecting sides.

Find the array factor and sketch the pattern of a 2 element array having equal amplitudes, phases, and having a spacing of d = λ.

How do you measure gain of an antenna using three antennas?

Obtain an expression for the BWFN of a broadside array, and compare the same with that of an End fire array.

What are the advantages of antenna arrays? Explain the types of antenna arrays.

Obtain the relation between skip distance and Maximum Usable Frequency.

Explain the effects of D and F layers of the ionosphere on propagation and estimate the critical frequency and MUF for a layer with 10¹¹/m³ electron density, and incident angle of 60^o.

Duct propagation

Fading.