1m-2m
1. In a high-frequency RF circuit, which chip capacitor size would be most
appropriate?
a) 50 mils square ✅ (Correct)
b) 200 mils square
c) 400 mils square
d) 600 mils square
2. In a high-speed digital circuit, which chip capacitor type would be most suitable?
a) Single-plate configuration
b) multiple-layer design ✅ (Correct)
c) Both types are equally suitable
d) None of the mentioned
3. A communication system requires high-frequency operation for satellite
communication. Which transmission line configuration is most suitable?
a) TEM line
b) Guided mode line
c) Optical fiber cable
d) waveguides ✅ (Correct)
4. The reflection coefficient of a matched load ideally should be for perfect
matching.
a) Zero ✅ (Correct)
b) Negative
c) Positive
d) Infinite
5. Which of the following statements is true regarding a lossless device?
a) Purely resistive impedance
b) Purely reactive impedance ✅ (Correct)
c) Purely resistive admittance
d) Purely reactive admittance
6. Assertion & Reason:
Assertion (A): In a lossless network, the delivered power at every port is zero.
Reason (R): Lossless devices do not absorb power.
c) A is false but R is true ✅ (Correct)
7. ____ devices exhibit symmetric impedance and admittance matrices, where Zmn
= Znm & Ymn = Ynm.
a) Lossless
b) Lossy
c) Reciprocal ✅ (Correct)
d) Non-reciprocal
8. In a lossless network, the elements of the impedance matrix are predominantly
_______.
a) resistive
b) reactive ✅ (Correct)
c) inductive
d) capacitive
9. Purpose of resistive layer trimming in chip resistors?
a) Adjust power rating
b) Reduce thickness
c) Achieve desired resistance ✅ (Correct)
d) Improve linearity
10. Which matrix is multiplied for cascaded two-port networks?
a) Scattering matrix
b) Admittance matrix
c) Impedance matrix
d) Transmission matrix ✅ (Correct)
11. Scattering matrix for a matched microwave network:
a) All non diagonal elements will be zero
b) All diagonal elements will be zero ✅ (Correct)
c) None will be zero
d) All elements zero
12. Condition for a reciprocal 2-port network:
a) Sij = Sji (i≠j) ✅ (Correct)
b) Sij = Sji (i=j)
c) Sij = 1/Sji (i≠j)
d) Sij ≠ Sji (i=j)
13. Benefit of using S-parameters:
a) Reduced power consumption
b) Increased capacitance
c) Reduced reflections ✅ (Correct)
d) Increased resistance
14. Disadvantage of carbon-composite resistors in high frequency:
a) They have high lead inductances ✅ (Correct)
b) They have low parasitic capacitances
c) They are not temperature stable
d) They cannot be small
15. Why open/short measurements are insufficient at high frequencies?
a) Absence of wire inductance
b) Absence of capacitive loading
c) Presence of wire inductance ✅ (Correct)
d) Presence of capacitive loading
Match the following:
1. Cascade → B
2. Series → C
3. Parallel → A
Answer: d) 1-B, 2-C, 3-A ✅ (Correct)
16. E bend min. radius for small reflection:
a) 1.5a ✅ (Correct)
b) 1.5b
c) 2a
d) 2b
17. H bend min. radius:
a) 1.5a
b) 1.5b ✅ (Correct)
c) 2a
d) 2b
18. Mean length between discontinuities in waveguide bend:
a) Even quarter wavelength ✅ (Correct)
b) Odd quarter wavelength
c) Full wavelength
d) Half wavelength
19. Wave fed into port 1 of a hybrid ring:
a) It appears at port 3 ✅ (Correct)
b) Canceled at port
c) Appears at port 2
d) Reflected back at port 1
20. Mode with 90° Faraday rotation in circular guide of microwave gyrator:
a) TE01
b) TE11 ✅ (Correct)
c) TM10
d) TM01
21. Assertion & Reason for H-Tee zero output with equal in-phase sources:
a) Both A and R are true and R is the correct explanation ✅ (Correct)
22. Matched loads are made using:
a) Inductive elements
b) Capacitive elements
c) Resistive elements ✅ (Correct)
d) Reactive elements
23. Primary purpose of movable shorts:
a) Impedance tuning and adjustment ✅ (Correct)
b) Power amplification
c) Signal modulation
d) Data transmission
24. How movable shorts minimize reflections:
a) Resistive properties
b) Short circuit creation
c) Adjustable electrical length ✅ (Correct)
d) Signal amplification
25. How isolators improve frequency stability:
a) Amplifying reflected power
b) Absorbing reflected power ✅ (Correct)
c) Increasing load impedance
d) Reducing generator power
26. Isolators can be made by inserting a:
a) Resistor
b) Capacitor
c) Ferrite rod ✅ (Correct)
d) Transformer
27. Why isolator is called "uniline":
a) Multiple directions
b) Only one direction ✅ (Correct)
c) Telecom use
d) Eliminates reflections
28. Power from port 1 to port 4 in microwave circulator:
a) Zero ✅ (Correct)
b) Half
c) Equal to power at port 1
d) Double
29. Two 3-dB couplers in circulator phase shift:
a) 45°
b) 90° ✅ (Correct)
c) 180°
d) 270°
30. Output power in H-Tee with equal in-phase sources:
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero ✅ (Correct)
31. Waves leaving main arms in H-plane Tee (equal lengths):
a) Out of phase ✅ (Correct)
b) In phase
c) Random
d) Irrelevant
32. H-plane Tee is classified as:
a) Current
b) Shunt
c) Parallel
d) Series ✅ (Correct)
33. Why E-Tee is called "3dB splitter":
a) Splits input into two equal parts ✅ (Correct)
b) Attenuates by 3dB
c) Combines signals with 3dB gain
d) Splits with -3dB
34. Condition for zero output in E-Tee combiner:
a) Equal input signals
b) Out-of-phase input signals ✅ (Correct)
c) Different lengths
d) Different powers
35. Magic-Tee is:
a) Modification of H-plane tee
b) Modification of E-plane tee
c) Combination of E & H plane ✅ (Correct)
d) Two E-plane tees in parallel
36. Type of junction for E-plane & H-plane Tee:
a) Four-port junction
b) Two-port junction
c) Three-port junction ✅ (Correct)
d) Single-port junction
1. Define reciprocal and symmetrical networks
Reciprocal network: a network where transmission is the same in both
directions (e.g. Zmn = Znm, Sij = Sji).
Symmetrical network: ports are identical and interchangeable so
input/output behaviours match.
Reciprocity is a physical property (no nonreciprocal elements like ferrites).
Symmetry relates to geometry/port equivalence.
2. A 5 dB attenuator VSWR = 1.2 — find S-parameters (reciprocal)
For a matched reciprocal attenuator, S11 ≈ S22 ≈ (VSWR−1)/(VSWR+1) ≈
(1.2−1)/(1.2+1)=0.091.
In dB, S21 (magnitude) = −5 dB ⇒ |S21| = 10^(−5/20)=0.5623.
Reciprocity gives S12 = S21 = 0.5623∠0°.
S11 and S22 are small reflections ≈0.091∠0°.
3. State the principle of Faraday’s rotation law
A magnetic field along the propagation direction causes the plane of
polarization of a wave to rotate.
Rotation angle ∝ magnetic flux density, path length and Verdet constant of
the medium.
Used in nonreciprocal devices (gyrators, isolators) due to time-odd
magneto-optic effect.
4. Limitations of measuring Z, Y, ABCD at high frequency
At HF/microwave, open/short techniques produce parasitic
inductance/capacitance.
Leads and fixtures add transmission effects, so lumped parameters lose
meaning.
S-parameters are preferred because they use matched ports and travel-
wave concept.
5. Summarize advantages of the ABCD matrix
ABCD (transmission) matrix cascades simply: overall T = T1·T2·...·TN.
Useful for series/chain two-ports and finding voltage/current relations.
Works with mismatched ports and converts readily to other parameter sets.
6. Problems caused by resistors at high frequency
Parasitic inductance from leads and resistor geometry increases impedance
with frequency.
Parasitic capacitance between resistor elements causes unwanted bypass
paths.
Skin effect and temperature coefficient change effective resistance and
introduce loss.
7. Classify RF bands available at microwave frequency range
Common microwave bands: L (1–2 GHz), S (2–4 GHz), C (4–8 GHz), X (8–12
GHz), Ku (12–18 GHz), K/Ka (18–40+ GHz).
Each band has specific applications (radar, satellite, comms).
8. Discuss properties of S-parameters
Defined with ports matched to reference impedances; relate incident and
reflected waves.
Frequency dependent, complex (magnitude and phase).
Easily measured with VNA; cascade via chain-scattering conversions.
9. Describe the transmission matrix with necessary equation
Transmission (ABCD) relates port 1 volt/current to port 2: [V1] = [A B; C D]
[V2].
V1 = A·V2 + B·I2, I1 = C·V2 + D·I2.
For cascaded networks, Ttotal = T1·T2.
10.Explain attenuation loss and return loss
Attenuation loss: reduction of signal power along a line, expressed in dB
(Pin/ Pout).
Return loss: measure of reflected power due to mismatch, RL(dB)= −20log10|
Γ|.
Higher return loss → better matching; higher attenuation → more signal
loss.
11.Fundamental characteristics and applications of microstrip lines
Single conductor trace over a ground plane separated by a dielectric (quasi-
TEM).
Characteristic impedance depends on width, thickness and substrate
permittivity.
Used in RF PCBs, filters, antennas, and matching networks up to microwave
frequencies.
12.Define reflection coefficient
Γ = (ZL − Z0)/(ZL + Z0), ratio of reflected to incident wave at a port.
Complex quantity with magnitude ≤1 for passive loads; phase indicates
phase shift.
13.Parameters used at low frequency for a two-port network
Z-parameters (impedance), Y-parameters (admittance), h-parameters
(hybrid), and ABCD.
They relate voltages and currents directly (suitable for lumped circuits).
14.Explain the phase shift property of S-matrix
Each Sij is complex: Sij = |Sij| e^{jθij}, where θij is the phase shift between
incident and scattered wave.
Phase varies with frequency and physical delays; important for matching,
delay and stability.
15.Explain Quality-factor (Q) of a capacitor
Q = |Xc|/Rloss = (1/ωC)/Rloss, ratio of reactive to resistive impedance.
High Q → low loss, desirable at RF; low Q indicates more dielectric or series
loss.
16.Distinguish reciprocal vs non-reciprocal devices
Reciprocal: Sij = Sji (transmission symmetric), e.g., passive networks without
magnetics.
Non-reciprocal: Sij ≠ Sji (directional behavior), realized using ferrites under
bias (isolators, circulators).
17.Explain the need of isolator in a microwave network
Isolators absorb/refuse reflected energy to protect sources and improve
stability.
They ensure power flows predominantly one way, preventing oscillations
from reflections.
18.Draw the equivalent circuit of practical capacitor
(practical cap) — series R (ESR) — series L (ESL) — ideal C to ground.
R accounts for dielectric/ohmic loss; L for lead/terminal inductance; C is the
capacitance.
19.List applications of magic Tee junction
Used for combining/splitting signals with phase isolation, mixers, balanced
amplifiers.
Used in duplexers, phase shifters and antenna feed networks for
symmetry/control.
20.Mention applications of directional coupler
Sampling forward/reflected power, power monitoring, duplexing, antenna
feed networks, and reflectometry.
Used in VSWR measurement and signal routing without disturbing main
line.
21.Explain transmission characteristics of hybrid ring
Hybrid ring (rat-race) provides ports with constructive/destructive
interference.
With proper feed, signal splits with specific phase shifts; isolated port sees
cancellation.
Useful for balanced mixers, combiners, and phase shifters.
22.Discuss construction of E-plane bend and H-plane bend
E-bend: bend in plane containing E-field (narrow dimension changes) —
radius refer to ‘a’ dimension.
H-bend: bend in plane containing H-field (broad dimension changes) —
radius refer to ‘b’ dimension.
Both require smooth curvature to reduce mode conversion and reflection.
23.Define coupling factor and directivity of a directional coupler
Coupling factor (dB): how much power is coupled to the coupled port
relative to input.
Directivity (dB): difference between coupled power from forward and
backward directions; measure of isolation between forward and reverse
coupling.
24.Analyse design and functionality of waveguide corners and twists
Corners/twists change waveguide direction or orientation; design uses
gradual bends and matched transitions.
Sharp discontinuities cause mode conversion and reflections; smooth radius
and matching structures minimize loss.
25.Illustrate a 4-port circulator and give its S-matrix
Circulator passes power 1→2, 2→3, 3→4, 4→1 nonreciprocally.
Ideal S-matrix (4-port): S_{i,i+1}=1, others 0 (index modulo 4). Example row
for port1: [0 1 0 0].
26.Describe the concept of matched load
A matched load has impedance equal to system Z0 so no reflection occurs
(Γ=0).
It absorbs incident power fully and is used for termination and testing.
27.Compare transmission of E-plane Tee and H-plane Tee
E-plane Tee splits electric field with equal amplitude and in-phase outputs
(depending on port).
H-plane Tee splits magnetic field and can produce out-of-phase outputs;
different port isolation and power flow properties.
28.Define insertion loss in dB
Insertion loss (dB) = −20 log10(|S21|) or 10 log10(Pin/Pout).
It quantifies loss introduced by inserting a device into the transmission path.
29.Identify component type with S11=S22=0, S21 ≠ S12
S11=S22=0 ⇒ matched at ports; S21 ≠ S12 indicates non-reciprocal,
directional device.
This describes an isolator/circulator (non-reciprocal two-port).
30.Why isolators are called uniline device? (2 marks)
Because they allow power transmission predominantly in one direction
only while isolating the reverse direction.
This one-way (single-line) behaviour protects sources from reflections and
ensures stable forward operation. (2 marks)
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mark cheat-sheet?
