(SEM. V) THEORY EXAMINATION 2017-2018 ANTENNA AND WAVE PROPAGATION

ANTENNA AND WAVE PROPAGATION (NEC-504)

B.Tech | Semester V | Section-wise Important Questions & Notes

SECTION A – Very Short Answer & Numericals (2 × 10 = 20)

This section mixes definitions + small numericals. Answers must be direct and formula-based.

 Important Questions

Explain Half Power Beam Width (HPBW) and First Null Beam Width (FNBW).

Explain the concept of point sources.

Define antenna temperature.

What is tapering? Explain with an example.

Numerical on radiation resistance, loss resistance, gain & directivity.

Uniform linear array numerical (HPBW & directivity).

Parabolic reflector numerical (area & HPBW).

Horn antenna numerical (power gain & directivity).

Define skip distance and virtual height.

Path difference numerical (time delay & phase difference).

 Key Notes

HPBW: Angle between half-power points of main lobe.

FNBW: Angle between first nulls.

Antenna temperature: Measure of noise power received by antenna.

Tapering: Varying amplitude of array elements to reduce side lobes.

Numerical questions are very frequent in this section.

 SECTION B – Long Theory & Derivations (Attempt Any 3)

This section focuses on core antenna theory and derivations.

 Important Questions

Explain Antenna Gain, Directivity, Beam Efficiency & Antenna Impedance.

Linear array of n isotropic sources – broadside array derivation.

Derive electric and magnetic field of a short dipole antenna.

Direction finding using loop antenna (short loop & large loop).

Explain:

Atmospheric noise             Maximum usable frequency (MUF)

Critical frequency               Skip distance

Key Notes
 

Directivity ≠ Gain (gain includes losses).                Broadside array → maximum radiation at 90°.

Short dipole is a fundamental antenna model.     MUF and critical frequency are very important for propagation.

SECTION C – Medium Answer & Numericals (5 × 2 = 10)

This section combines numericals + conceptual short notes.

Important Questions

Numerical on antenna efficiency, power loss & directive gain.

Short notes on:

Directivity and resolution

Radio communication link

Explain antenna aperture and derive relation between aperture & directivity.

Key Notes

Antenna efficiency = Radiated power / Input power.

Effective aperture is directly related to antenna directivity.

Always show units and stepwise calculation.