Difficulty: Easy & Basic
Long microwave amplifier needs wide bandwidth. Which tube uses an electron beam and slow-wave structure?
A Magnetron
B Traveling-wave tube
C Schottky diode
D PIN attenuator
Answer: B. Traveling-wave tube. A TWT amplifies RF through interaction between an electron beam and a traveling wave on a slow-wave structure.
In a TWT, what does its slow-wave structure do?
A Slows RF phase
B Stops electron motion
C Stores audio data
D Rectifies the beam
Answer: A. Slows RF phase. It reduces the wave’s phase velocity so it can interact with the electron beam.
Which electrode sends electrons back through the cavity in a reflex klystron?
A Collector
B Repeller
C Anode strap
D Ferrite puck
Answer: B. Repeller. The repeller reverses the electron beam for another cavity interaction.
In a multicavity klystron amplifier, what is the first cavity commonly called?
A Collector
B Output horn
C Isolator
D Buncher
Answer: D. Buncher. The buncher cavity velocity-modulates the electron beam.
Which semiconductor microwave oscillator uses transferred-electron negative resistance?
A PIN diode
B Gunn diode
C Schottky diode
D Varactor diode
Answer: B. Gunn diode. The Gunn effect produces a negative-resistance region used for microwave oscillation.
Which diode relies on avalanche and transit-time effects for microwave generation?
A LED
B Zener only
C IMPATT
D Photodiode
Answer: C. IMPATT. IMPATT devices use impact ionization and transit-time delay.
A low-capacitance junction is useful for microwave mixing. Which diode commonly fits?
A Power rectifier
B Photovoltaic cell
C Schottky diode
D Zener clamp
Answer: C. Schottky diode. Schottky diodes are widely used in microwave mixers and detectors.
Which diode changes junction capacitance when reverse bias changes?
A Varactor
B PIN
C Gunn
D IMPATT
Answer: A. Varactor. A varactor uses voltage-dependent junction capacitance for tuning.
Which diode is widely used as an RF switch or attenuator element?
A Gunn diode
B LED
C PIN diode
D Photodiode
Answer: C. PIN diode. PIN diodes provide useful RF resistance changes for switching and attenuation.
A signal enters the side arm of an ideal E-plane tee. How do the collinear outputs relate?
A Opposite phase
B Same phase
C DC level
D Random phase
Answer: A. Opposite phase. The E-plane tee produces a phase reversal between its collinear arms.
With input at its side arm, an ideal H-plane tee produces collinear outputs in what relation?
A Opposite phase
B Same phase
C Quadrature
D No output
Answer: B. Same phase. The H-plane tee splits the side-arm signal in phase between collinear arms.
What does a magic tee combine in one four-port microwave junction?
A Two waveguide loads
B Two attenuators
C Four isolators
D E and H tees
Answer: D. E and H tees. A magic tee combines E-plane and H-plane tee properties.
Which hybrid ring is commonly called a rat-race junction?
A 90-degree hybrid
B One-port resonator
C 180-degree hybrid
D Waveguide filter
Answer: C. 180-degree hybrid. A rat-race hybrid provides sum and difference behavior with 180-degree relationships.
Why is a waveguide taper placed between unequal guide sizes?
A Generate oscillation
B Measure frequency
C Absorb all power
D Reduce mismatch
Answer: D. Reduce mismatch. A gradual transition can improve impedance matching between sections.
A waveguide twist primarily changes what?
A Carrier frequency
B Field orientation
C Signal coding
D Cutoff mode
Answer: B. Field orientation. A twist rotates the field orientation to suit the connected component.
In a slotted-line setup, what does moving the probe locate?
A Standing-wave maxima
B Electron bunches
C Antenna licence
D Magnetron cathode
Answer: A. Standing-wave maxima. Probe readings along the line reveal maxima and minima for VSWR analysis.
A cavity-based wavemeter is used to determine what?
A Noise figure only
B Microwave frequency
C Cable length only
D Antenna polarization
Answer: B. Microwave frequency. A wavemeter identifies frequency through a tuned resonant response.
Which component converts incident microwave power into a measurable voltage?
A Waveguide twist
B Matched flange
C Directional coupler
D Crystal detector
Answer: D. Crystal detector. A crystal or diode detector rectifies RF energy for measurement.
During a bench measurement, a variable attenuator adjusts what?
A Waveguide mode
B Carrier polarization
C Signal level
D Cavity dimensions
Answer: C. Signal level. The attenuator provides controlled reduction of microwave power.
At the end of a waveguide test setup, what absorbs incident power with little reflection?
A Open flange
B Shorting plate
C Waveguide bend
D Matched termination
Answer: D. Matched termination. A matched load absorbs the guided power and minimizes reflections.
Why can a hollow waveguide be useful for high-power microwave transmission?
A Needs no dimensions
B Supports DC perfectly
C Has zero cutoff
D High power handling
Answer: D. High power handling. Waveguides can carry substantial RF power when operated within their design limits.
Which transmission line has a conductor over a dielectric substrate and ground plane?
A Microstrip
B Rectangular waveguide
C Twin-lead only
D Hollow cavity
Answer: A. Microstrip. Microstrip is a planar line formed over a dielectric with a ground plane.
In stripline, where is the signal conductor located?
A Between ground planes
B Outside the shield
C Inside a hollow guide
D Above one ground plane
Answer: A. Between ground planes. Stripline places its conductor within dielectric between ground planes.
As frequency rises, what happens to conductor skin depth?
A It increases
B It stays constant
C It decreases
D It becomes infinite
Answer: C. It decreases. Skin depth decreases approximately with the inverse square root of frequency.
Microwave heating of food mainly occurs through which interaction?
A Dielectric loss
B Magnetic levitation
C Electron bunching
D Waveguide cutoff
Answer: A. Dielectric loss. Lossy polar materials absorb RF energy and convert it to heat.