EC-702-A Microwave Engineering - 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
   aDiscuss the general representation of EM field in terms of TEM, TE and TM components.
   How to answer

   • Define TEM, TE, TM with field components Ez, Hz conditions
   • Write Maxwell equations for guided wave with e^{-j\beta z} dependence
   • Show transverse-longitudinal decomposition formulas
2. 7 Marks
   bWrite and explain the classification of different waveguide structures, also explain its operating principle.
   How to answer

   • List waveguide types: rectangular, circular, ridged, microstrip etc.
   • Classify by structure and mode support
   • Explain operating principle of guided propagation and cutoff
3. 7 Marks
   aA rectangular waveguide with dimension of $3\times 2$ cms operates in TM11 mode at $10$ GHz. Determine the characteristic wave impedance.
   How to answer

   • Calculate cutoff frequency/wavenumber for $TM_{11}$ with $a=3$ cm, $b=2$ cm
   • Calculate free-space impedance $\eta$ and $f_c/f$ ratio
   • Apply $Z_{TM}=\eta\sqrt{1-(f_c/f)^2}$ to get characteristic wave impedance
4. 7 Marks
   bDiscuss some of the properties of Dominant mode.
   How to answer

   • Define dominant mode e.g. $TE_{10}$ in rectangular guide
   • Explain lowest cutoff frequency and field pattern
   • List properties: low loss, bandwidth, single-mode operation
5. 7 Marks
   aDerive a general band width relation for Micro strip and rectangular waveguides.
   How to answer

   • Define bandwidth limited by cutoff of dominant and next higher mode
   • Derive $f_c$ expressions for microstrip quasi-TEM and rectangular $TE_{10}$
   • Obtain fractional bandwidth relation
6. 7 Marks
   bDiscuss the dominant and higher order modes in strip line structure.
   How to answer

   • Describe stripline geometry and quasi-TEM dominant mode
   • Explain higher order TE/TM and parallel-plate modes
   • Discuss cutoff conditions and suppression
7. 7 Marks
   aWrite and explain the properties of Scattering matrix of reciprocal network.
   How to answer

   • Define scattering matrix $[S]$ for N-port network
   • Prove symmetry $S_{ij}=S_{ji}$ for reciprocal network
   • Prove unitary property for lossless case
8. 7 Marks
   bWhat do you mean by directional couplers? Explain their basic derivative parameters.
   How to answer

   • Define directional coupler with 4 ports
   • Explain coupling, directivity, isolation, insertion loss
   • Give S-matrix and example values
9. 7 Marks
   aExplain the working principle of two cavity klystron. Discuss some of its applications.
   How to answer

   • Draw two-cavity klystron with buncher and catcher cavities
   • Explain velocity modulation, bunching and energy extraction
   • List applications in radar, UHF TV, accelerators
10. 7 Marks
    bDraw and explain the block diagram of frequency converters using varactor diodes.
    How to answer

    • Draw block diagram with varactor, pump, filters for up/down conversion
    • Explain nonlinear capacitance and Manley-Rowe interaction
    • Show input, pump and output frequency relations
11. 7 Marks
    aDiscuss some of the properties of ferrites, isolators and phase shifters.
    How to answer

    • Define ferrites and Faraday rotation / non-reciprocity
    • Explain isolator operation and S-matrix
    • Explain latching / Faraday phase shifter types
12. 7 Marks
    bDerive and explain Manley Rowe power relation.
    How to answer

    • State Manley-Rowe relations $\sum mP_{mn}/(mf_1+nf_2)=0$ etc.
    • Derive from power conservation in nonlinear reactance
    • Explain up-converter vs down-converter power gain implications
13. 7 Marks
    aExplain the principle of VSWR meter. How it works? Explain with suitable example.
    How to answer

    • Define VSWR and slotted-line / bridge principle
    • Explain detector, calibration and meter reading
    • Give example measurement of load VSWR
14. 7 Marks
    bDiscuss about the network analyzer and its use in measurements.
    How to answer

    • Define network analyzer for S-parameter measurement
    • Explain stimulus, test set, receivers and calibration
    • List uses: filter, antenna, amplifier characterization
15. 14 Marks
    Write short note (Any four)

    1. a)TWT amplifier
    2. b)BARITT
    3. c)Gunn Oscillator
    4. d)Tee junction of waveguides
    5. e)Tuned detectors
    How to answer

    • Define each device with principle and diagram
    • Give construction, working and key formulas
    • Mention microwave applications