EC-602 Antenna and Wave Propagation - Jun 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aWhat is the concept of retarded potential? Explain how it accounts for the finite speed of electromagnetic wave propagation and its importance in radiation theory.
   How to answer

   • Definition of retarded potentials for scalar and vector potentials with time delay R/c
   • Explanation of finite propagation speed vs static potentials
   • Mathematical form with retarded time t-R/c
   • Importance in radiation theory - source to far-field causality
2. 7 Marks
   bExplain the working principle of a quarter-wave monopole antenna. Derive the expressions for the radiation pattern and discuss its applications.
   How to answer

   • Working principle of quarter-wave monopole with ground plane and image theory
   • Current distribution and radiation mechanism
   • Derivation of far-field radiation pattern expression
   • Applications in mobile, broadcast and communication systems
3. 7 Marks
   aDiscuss the significance of the far-field approximation in antenna design and analysis.
   How to answer

   • Definition of far-field region and Fraunhofer criteria
   • Simplifications in field expressions - plane wave approximation
   • Significance for pattern, gain, directivity measurement
   • Role in antenna design and testing
4. 7 Marks
   bWhat are the directional properties of dipole antennas. Analyze the influence of dipole length and feed-point position on its directional properties.
   How to answer

   • Directional properties - radiation pattern, directivity, beamwidth
   • Effect of dipole length on pattern and lobes
   • Effect of feed-point position on current and radiation
   • Examples of half-wave vs short vs long dipole
5. 7 Marks
   aDescribe horizontal patterns in broadcast antenna arrays. How do they influence the coverage area of AM/FM broadcast systems?
   How to answer

   • Concept of horizontal plane pattern in broadcast arrays
   • Array configuration to achieve omnidirectional or shaped pattern
   • Influence on coverage area and field uniformity
   • AM/FM broadcast application considerations
6. 7 Marks
   bExplain how the conductivity and permittivity of the ground impact the vertical patterns of antennas.
   How to answer

   • Role of ground conductivity and permittivity in reflection
   • Effect on vertical pattern shape, nulls and lobes
   • Ground losses and surface wave excitation
   • Illustration with vertical antenna over real ground
7. 7 Marks
   aExplain the working principle of a log-periodic antenna. How does its structure enable wideband operation?
   How to answer

   • Log-periodic principle - scaling and periodicity with frequency
   • Active region concept and phasing
   • Structural features - toothed dipoles, scale factor tau
   • How structure gives wideband impedance and pattern
8. 7 Marks
   bDiscuss about the radiation pattern and design principles of a long wire antenna. How does its length influence its performance?
   How to answer

   • Long wire antenna geometry and travelling wave current
   • Radiation pattern with multiple lobes
   • Design principles - height, length in wavelengths, termination
   • Effect of increasing length on directivity and lobe number
9. 7 Marks
   aExplain the construction and operation of a Yagi-Uda antenna. Discuss the roles of the reflector and directors in shaping the radiation pattern.
   How to answer

   • Construction - driven element, reflector, directors and spacing
   • Operation - parasitic excitation and Yagi effect
   • Role of reflector in back-lobe suppression
   • Role of directors in forward gain and pattern narrowing
10. 7 Marks
    bDiscuss the transition between surface and space waves in ground wave propagation. How does terrain affect this transition?
    How to answer

    • Surface wave vs space wave components in ground wave
    • Transition mechanism with distance and frequency
    • Effect of terrain roughness, conductivity, obstacles
    • Implication for coverage and field strength
11. 7 Marks
    aDescribe the effects of the environment on the propagation of radio waves. Explain how atmospheric conditions, terrain and obstacles influence wave behavior.
    How to answer

    • Environment factors - atmosphere, terrain, obstacles
    • Atmospheric refraction, absorption and ducting
    • Terrain diffraction, reflection and shadowing
    • Obstacles causing multipath and fading
12. 7 Marks
    bDiscuss the phenomena of super refraction and scattering in space wave propagation. How do they affect the transmission of signals?
    How to answer

    • Definition of super refraction and scattering phenomena
    • Mechanism in troposphere - refractive index gradients
    • Effect on range, signal strength and fading
    • Impact on reliable signal transmission
13. 7 Marks
    aWhat are Slot antennas? Derive the expression for the radiation pattern of a rectangular slot in an infinite ground plane.
    How to answer

    • Definition of slot antenna and Babinet's principle
    • Rectangular slot in infinite ground plane geometry
    • Derivation steps for far-field pattern expression
    • Resultant pattern characteristics and polarization
14. 7 Marks
    bDiscuss the advantages of tapered apertures over uniform apertures and explain its application in reducing side lobe levels in antenna systems.
    How to answer

    • Uniform vs tapered aperture illumination concept
    • Advantages - lower side lobes, improved pattern
    • Trade-off with gain and beamwidth
    • Application in side lobe reduction in arrays and apertures
15. 14 Marks
    Write a short note on any two:

    1. a)Oscillating Electric Dipole
    2. b)Turnstile antenna
    3. c)Relation between MUF and skip distance
    4. d)Numerical tool for antenna analysis
    How to answer

    • Brief principle and key features of chosen topics
    • Relevant diagrams/formulas for each note
    • Applications and significance
    • Comparison or relation where applicable e.g. MUF vs skip distance