EC-602 Antenna and Wave Propagation - May 2024 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
   aDerive an equation of potential function for sinusoidal operations of an antenna.
   How to answer

   • Define retarded vector and scalar potentials for time-harmonic sources
   • Start from Maxwell equations with sinusoidal $e^{j\omega t}$ dependence
   • Derive wave equations for $\mathbf{A}$ and $\Phi$
   • Give integral solutions with $e^{-jkr}/r$ factor
2. 7 Marks
   bWrite some of the practical applications of short antenna.
   How to answer

   • Define short antenna / Hertzian dipole
   • List practical applications e.g. AM broadcast, portable, measurement
   • Mention advantages for low frequency
   • Brief use-case explanation
3. 7 Marks
   aWhat do you mean by antenna? Write some of the properties of antenna.
   How to answer

   • Define antenna as transducer between guided wave and free space
   • Explain transmit and receive function
   • List properties: gain, directivity, efficiency, bandwidth, polarization, impedance
   • Brief meaning of each property
4. 7 Marks
   bDerive a relation and find necessary equations for transmission between the two antennas.
   How to answer

   • Consider two antennas for transmit-receive link
   • Apply reciprocity / Friis concept with effective apertures
   • Derive Friis transmission equation $P_r/P_t$ vs $G_t,G_r,\lambda,R$
   • State assumptions and necessary equations
5. 7 Marks
   aWhat do you mean by Antenna Gain? Give a brief classification of Gain and explain each one.
   How to answer

   • Define antenna gain vs directivity
   • Classify: absolute, relative, partial, realized gain
   • Give formulas $G = \eta D$
   • Explain each type briefly
6. 7 Marks
   bDerive and explain the relation of antenna efficiency and effective length of an antenna.
   How to answer

   • Define radiation efficiency and effective length
   • Relate radiated power, input power and current distribution
   • Derive relation $l_e$ vs physical length and efficiency
   • Explain physical significance
7. 7 Marks
   aExplain Babinet's principle and complementary antenna.
   How to answer

   • State Babinet's principle in optics and EM form
   • Define complementary screens / antennas
   • Relate impedances $Z_1 Z_2 = \eta^2/4$
   • Example: slot vs dipole
8. 7 Marks
   bDiscuss the pattern multiplication of an antenna. Explain the effect of earth on vertical patterns.
   How to answer

   • Define pattern multiplication: element pattern x array factor
   • Give mathematical expression for total pattern
   • Explain image theory for earth effect
   • Discuss effect on vertical patterns for horizontal/vertical antennas
9. 7 Marks
   aExplain folded dipole antenna. Derive the current equation for this antenna.
   How to answer

   • Describe construction of folded dipole
   • Explain two-wire mode and current division
   • Derive input impedance ~4x dipole and current equation
   • Mention advantages: bandwidth, matching
10. 7 Marks
    bDraw and explain all the characteristics and properties of Yagi Uda Antenna.
    How to answer

    • Draw Yagi-Uda with reflector, driven element, directors
    • Explain operation and parasitic excitation
    • List characteristics: gain, directivity, bandwidth, impedance
    • Mention applications e.g. TV reception
11. 7 Marks
    aDiscuss the Taylor synthesis of sum patterns of an antenna array system.
    How to answer

    • Define array synthesis and sum pattern requirement
    • Explain Taylor distribution for controlled sidelobes
    • Give design steps and taper coefficients
    • Mention trade-off sidelobe level vs beamwidth
12. 7 Marks
    bDraw and explain the Schelkunoff unit circle with the help of suitable example.
    How to answer

    • Define Schelkunoff polynomial $W(z)$ with $z=e^{j\psi}$
    • Draw unit circle in complex z-plane with roots/zeros
    • Illustrate with example e.g. broadside array
    • Explain null locations and visible region
13. 7 Marks
    aDiscuss some of the fundamentals of electromagnetic waves. Discuss the types of radio waves propagation.
    How to answer

    • Define EM waves: $E$, $H$, propagation, polarization
    • Explain Maxwell basis, velocity, impedance
    • Classify radio propagation: ground, sky, space/tropospheric
    • Give frequency ranges and examples
14. 7 Marks
    bDiscuss the super refraction. Also explain the tropospheric propagation.
    How to answer

    • Define super-refraction and modified refractive index
    • Explain duct formation conditions
    • Define tropospheric scatter/duct propagation
    • Explain effects on range and fading
15. 14 Marks
    Write short notes (any four)

    1. a)MUF
    2. b)LUF
    3. c)Skip Distance
    4. d)Parabolic Reflector Antenna
    5. e)Binomial Array
    6. f)Virtual height
    How to answer

    • Select any four items from list
    • Give definition, formula and significance for each
    • Add neat sketch where applicable e.g. parabolic reflector
    • Mention typical values / applications