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ENEX 411Bachelor in Electronics, Communication and Information Engineering · Semester 71 Paper Available

RF and Microwave Engineering

Past examination question papers and complete curriculum syllabus for RF and Microwave Engineering (ENEX 411), Bachelor in Electronics, Communication and Information Engineering Semester 7 under Institute of Engineering (IOE), Tribhuvan University.

Past Question Papers (PDF)

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Note: This question paper file (8th sem) was archived from an IOE exam session for the common RF and Microwave Engineering curriculum.

8th-sem_RF and Microwave Engineering.pdf

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Most Frequently Asked Questions

Top recurring IOE board exam questions for RF and Microwave Engineering with verified mark schemes, formula notation, and recurrence frequency.

Showing 30 of 30 top repeated questions

Introduction to Microwave Engineering and Transmission Lines

4 Questions
#1Repeated 3 Times[8 Marks]Introduction to Microwave Engineering and Transmission Lines
A load impedance $Z_L = 110 + j110\ \Omega$ (or $75 + j100\ \Omega$) is connected to a $50\ \Omega$ lossless transmission line. Using the Smith Chart, determine: (a) Voltage Reflection Coefficient $\Gamma_L$, (b) Standing Wave Ratio (SWR), (c) Input impedance at a distance $0.2\lambda$ from load, and (d) Locations of voltage maxima and minima.
Appeared in:2080 Chaitra2079 Chaitra2073 Magh
#2Repeated 3 Times[8 Marks]Introduction to Microwave Engineering and Transmission Lines
Design a single-stub (shunt or series, open or short-circuited) impedance matching network to match an arbitrary load impedance to a $50\ \Omega$ transmission line using the Smith Chart. Calculate the stub position from the load and stub electrical length.
Appeared in:2080 Chaitra2079 Chaitra2071 Magh
#3Repeated 3 Times[6 Marks]Introduction to Microwave Engineering and Transmission Lines
Explain how microwave systems differ from conventional low-frequency lumped circuits. Compare lumped and distributed circuit models, and explain skin depth and dielectric loss at microwave frequencies.
Appeared in:2080 Chaitra2079 Chaitra2073 Magh
#4Repeated 3 Times[8 Marks]Introduction to Microwave Engineering and Transmission Lines
Explain Single-Stub and Double-Stub Shunt Impedance Matching using the Smith Chart. For a load $Z_L = 100 + j80\ \Omega$ connected to a $50\ \Omega$ line, determine the location and length of a short-circuited shunt stub.
Appeared in:2082 Chaitra2080 Chaitra2079 Chaitra

Waveguides and Cavity Resonators

3 Questions
#1Repeated 3 Times[10 Marks]Waveguides and Cavity Resonators
Derive electromagnetic field equations for TE and TM modes in a Rectangular Waveguide. Define and derive expressions for cutoff frequency ($f_c$), guide wavelength ($\lambda_g$), phase velocity ($v_p$), and wave impedance ($Z_{\text{TE}}$ and $Z_{\text{TM}}$). Explain why $TE_{10}$ is the dominant mode.
Appeared in:2080 Chaitra2077 Chaitra2073 Magh
#2Repeated 3 Times[8 Marks]Waveguides and Cavity Resonators
Derive the cut-off frequency $f_c = \frac{c}{2\pi}\sqrt{(m\pi/a)^2 + (n\pi/b)^2}$, guide wavelength $\lambda_g = \frac{\lambda_0}{\sqrt{1 - (f_c/f)^2}}$, and wave impedance for the $TE_{10}$ dominant mode in a rectangular waveguide. Why cannot TEM waves propagate inside a hollow single-conductor waveguide?
Appeared in:2082 Chaitra2080 Chaitra2078 Bhadra
#3Repeated 3 Times[8 Marks]Waveguides and Cavity Resonators
Explain Rectangular Cavity Resonators. Derive the resonant frequency formula $f_{mnp} = \frac{c}{2}\sqrt{(m/a)^2 + (n/b)^2 + (p/d)^2}$ and quality factor ($Q$) of the dominant $TE_{101}$ mode resonator.
Appeared in:2082 Chaitra2081 Chaitra2077 Magh

Microwave Passive Components and Scattering Matrix

8 Questions
#1Repeated 4 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Explain the Insertion Loss method for microwave filter design. Describe Richard's Transformation and Kuroda's Identities for converting lumped element prototype low-pass filters into distributed microstrip transmission line stubs.
Appeared in:2079 Chaitra2075 Bhadra2074 Bhadra2073 Magh
#2Repeated 3 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Why are Scattering Parameters (S-parameters) preferred over Z, Y, and h parameters at microwave frequencies? Define the S-matrix for a two-port and three-port network and prove that for a lossless reciprocal network, $[S]^T = [S]$ and $[S]^\dagger [S] = [I]$.
Appeared in:2080 Chaitra2079 Chaitra2073 Magh
#3Repeated 3 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Explain the construction, operational principle, and derive the S-matrix of a Magic Tee (Hybrid Tee). Show that the E-arm and H-arm are mutually decoupled, and explain its applications as a duplexer or balanced mixer.
Appeared in:2080 Chaitra2079 Chaitra2076 Bhadra
#4Repeated 3 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Define coupling factor ($C$), directivity ($D$), and isolation ($I$) of a Directional Coupler. Explain the working principle and S-matrix of a two-hole waveguide directional coupler and a Bethe-hole directional coupler.
Appeared in:2079 Chaitra2075 Bhadra2073 Bhadra
#5Repeated 3 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Explain the Magic-Tee (Hybrid-Tee) microwave junction. Derive its $4 \times 4$ Scattering Matrix ($S$-matrix) from symmetry and unitary properties, and explain its applications as an E-H tuner, duplexer, and balanced mixer.
Appeared in:2082 Chaitra2081 Chaitra2078 Kartik
#6Repeated 3 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Describe Directional Couplers. Define Coupling Factor ($C = 10\log_{10}(P_1/P_3)$), Directivity ($D = 10\log_{10}(P_3/P_4)$), and Isolation ($I = 10\log_{10}(P_1/P_4)$). Explain the Bethe-hole coupler and two-hole directional coupler.
Appeared in:2082 Chaitra2080 Chaitra2076 Chaitra
#7Repeated 3 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Explain Ferrite Microwave Devices: Faraday Rotation Isolators and Circulators. Derive the $3 \times 3$ S-matrix of an ideal 3-port circulator and explain non-reciprocal phase shift under external DC magnetic bias.
Appeared in:2082 Chaitra2081 Chaitra2079 Chaitra
#8Repeated 2 Times[8 Marks]Microwave Passive Components and Scattering Matrix
Explain Faraday Rotation in microwave ferrites. Describe the operational principle, internal structure, and scattering matrix of Microwave Isolators and Circulators.
Appeared in:2075 Bhadra2073 Magh

Microwave Semiconductor Devices

5 Questions
#1Repeated 4 Times[10 Marks]Microwave Semiconductor Devices
For a microwave transistor with given S-parameters at $5\text{ GHz}$, check unconditional stability using Rollet's stability criteria: $K > 1$ and $|\Delta| < 1$, where $\Delta = S_{11}S_{22} - S_{12}S_{21}$ and $K = \frac{1 - |S_{11}|^2 - |S_{22}|^2 + |\Delta|^2}{2|S_{12}S_{21}|}$. Plot input and output stability circles on the Smith Chart.
Appeared in:2080 Chaitra2079 Chaitra2075 Bhadra2071 Magh
#2Repeated 3 Times[8 Marks]Microwave Semiconductor Devices
Design input and output matching networks for a microwave transistor amplifier to achieve maximum transducer power gain ($G_{T,\max}$) or specified unilateral gain ($G_U$) with matching stubs on a $50\ \Omega$ microstrip line.
Appeared in:2080 Chaitra2079 Chaitra2071 Magh
#3Repeated 3 Times[8 Marks]Microwave Semiconductor Devices
Explain the Gunn Diode oscillator based on the Ridley-Watkins-Hilsum (RWH) transferred electron mechanism. Describe negative differential resistance, GaAs conduction band valleys ($\Gamma$ and $L$), and high-field domain transit modes.
Appeared in:2082 Chaitra2080 Chaitra2078 Kartik
#4Repeated 3 Times[8 Marks]Microwave Semiconductor Devices
Describe IMPATT and TRAPATT avalanche transit-time diodes. Explain impact ionization avalanche breakdown, $90^\circ$ phase delay, drift transit delay, and dynamic negative resistance generation.
Appeared in:2082 Chaitra2081 Chaitra2077 Magh
#5Repeated 2 Times[8 Marks]Microwave Semiconductor Devices
Explain the transferred electron mechanism (Gunn Effect and Ridley-Watkins-Hilsum theory) in a GaAs Gunn Diode. Describe the formation and drift of high-field dipole domains.
Appeared in:2079 Chaitra2075 Bhadra

Microwave Tubes (Klystron, TWT, Magnetron)

6 Questions
#1Repeated 3 Times[10 Marks]Microwave Tubes (Klystron, TWT, Magnetron)
What is velocity modulation and bunching effect? Describe the construction, operational principle, and Applegate diagram of a Two-Cavity Klystron amplifier and Reflex Klystron oscillator.
Appeared in:2080 Chaitra2079 Chaitra2071 Bhadra
#2Repeated 3 Times[8 Marks]Microwave Tubes (Klystron, TWT, Magnetron)
Describe the Reflex Klystron oscillator. Explain velocity modulation, bunching process with Applegate diagram, repeller voltage modes ($n + 3/4$), electronic tuning, and power output efficiency.
Appeared in:2082 Chaitra2080 Chaitra2077 Magh
#3Repeated 3 Times[8 Marks]Microwave Tubes (Klystron, TWT, Magnetron)
Explain the Two-Cavity Klystron amplifier: Bunched electron beam dynamics, bunching parameter, cavity gap transit angle, and RF power amplification mechanism.
Appeared in:2082 Chaitra2081 Chaitra2078 Bhadra
#4Repeated 3 Times[8 Marks]Microwave Tubes (Klystron, TWT, Magnetron)
Explain the Traveling Wave Tube (TWT) amplifier. Describe the slow-wave helical structure, continuous beam-wave interaction, axial phase velocity synchronism, and gain mechanism.
Appeared in:2082 Chaitra2080 Chaitra2076 Chaitra
#5Repeated 3 Times[8 Marks]Microwave Tubes (Klystron, TWT, Magnetron)
Explain the Cylindrical Magnetron oscillator. Describe crossed-field dynamics ($E \perp B$), Hull cut-off magnetic field, Hartree resonance condition, $\pi$-mode oscillation, and strapping techniques.
Appeared in:2082 Chaitra2081 Chaitra2079 Chaitra
#6Repeated 2 Times[8 Marks]Microwave Tubes (Klystron, TWT, Magnetron)
Explain the operational principle of a Cavity Magnetron oscillator. Describe electron trajectory under crossed electric and magnetic fields, phase focusing effect, and Hull cutoff magnetic field / Hartree condition.
Appeared in:2079 Chaitra2074 Bhadra

Microwave Measurements and Applications

4 Questions
#1Repeated 4 Times[8 Marks]Microwave Measurements and Applications
Explain microwave power measurement using Bolometer bridges (thermistors and barretters) and static calorimeters. Describe the operation and calibration of a Vector Network Analyzer (VNA) for measuring device S-parameters.
Appeared in:2080 Chaitra2079 Chaitra2076 Bhadra2075 Bhadra
#2Repeated 4 Times[6 Marks]Microwave Measurements and Applications
Define Specific Absorption Rate (SAR) and power density. Discuss microwave electromagnetic radiation biological hazards (thermal cataracts, tissue heating) and list major international RF safety standards and practices.
Appeared in:2080 Chaitra2079 Chaitra2075 Bhadra2073 Bhadra
#3Repeated 3 Times[8 Marks]Microwave Measurements and Applications
Explain Microwave Power and VSWR Measurements. Describe the Bolometer/Thermistor sensor bridge, slotted line method for measuring high and low VSWR (double minimum method), and frequency meter cavity operation.
Appeared in:2082 Chaitra2080 Chaitra2078 Bhadra
#4Repeated 3 Times[6 Marks]Microwave Measurements and Applications
Explain Microwave Radiation Hazards and IEEE/ICNIRP Safety Standards. Discuss Specific Absorption Rate (SAR in W/kg), thermal and non-thermal biological effects of microwave exposure, and maximum permissible exposure limits.
Appeared in:2082 Chaitra2081 Chaitra2079 Chaitra

Curriculum Syllabus & Course Topics

Sourced from TU curriculum portal
Full Syllabus (PDF)
Chapter-wise Units & Micro-Syllabus Topics (6 Units)

  1. 1. Introduction to Microwave Engineering and Transmission Lines

    6

  2. 2. Waveguides and Cavity Resonators

    8

  3. 3. Microwave Passive Components and Scattering Matrix

    8

  4. 4. Microwave Semiconductor Devices

    6

  5. 5. Microwave Tubes (Klystron, TWT, Magnetron)

    8

  6. 6. Microwave Measurements and Applications

    9

Examination Scheme & Marks Distribution

Evaluation Structure

  • Final Board Theory Exam: 60 Marks (Pass mark: 24)
  • Internal Assessment: 40 Marks (Pass mark: 16)
  • Practical / Lab Exam: 25 or 50 Marks (Continuous lab evaluation + viva, where applicable)

* This is the general current IOE 60/40 scheme; verify course-specific details in the syllabus above.

Exam Preparation Guidelines

  • Review the available past examination paper to understand question styling, typical derivation topics, and marks allocation.
  • Cross-reference key answers with official syllabus units, standard textbooks, and lecture notes.
  • Structure answers with labeled diagrams, concise bullet points, and highlight final answers in numerical solutions.

Frequently Asked Questions (RF and Microwave Engineering)

Q: How can I download RF and Microwave Engineering past question papers?

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Q: What is the pass mark for RF and Microwave Engineering?

The general current scheme is a 60-mark final theory exam and a 40-mark internal assessment, with pass marks of 24 and 16. Verify the course-specific syllabus above.

Q: Where can I find the complete syllabus for this subject?

The available chapter-wise syllabus and topic breakdown is indexed in the Syllabus section above, with links to the curriculum PDF source.

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