MCQ in Microwave Communications Part 7 | ECE Board Exam

This is the Multiples Choice Questions Part 7 of the Series in Microwave Communications as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Basic Principles of Microwave Communications
• MCQ in Electro-Optics
• MCQ in Photonics
• MCQ in Optoelectronics
• MCQ in Electromagnetics
• MCQ in Avionics, Aerospace, Navigational and Military Applications
• MCQ in Medical Electronics
• MCQ in Cybernetics
• MCQ in Biometrics

Continue Practice Exam Test Questions Part 7 of the Series

301. A type of tee so-named because of the side arms shunting the E field for the TE modes, which is analogous to voltage in the transmission lines

a) magic tee

b) rat tee

c) series tee

d) shunt tee

302. Which one of the following waveguide tuning components is not easily adjustable?

a) screw

b) stub

c) iris

d) plunger

303. What type of waveguide is widely used?

a) circular

b) ridged

c) flexible

d) rectangular

304. A piston attenuator is a

a) vane attenuator

b) waveguide below cutoff

c) mode filter

d) flap attenuator

305. Waveguides act as _________.

a) low-pass filter

b) bandpass filter

c) high-pass filter

d) band-stop filter

306. Cylindrical cavity resonators are not used with klystron because they have

a) a Q that is too low

b) a shape whose resonant frequency is too difficult to calculate

c) harmonically related resonant frequencies

d) too heavy losses

307. In waveguides, if no component of the E field is in the direction of propagation the mode is said to be

a) TE

b) TM

c) TEM

d) TME

308. A directional coupler with three or more holes is sometimes used in preference to the two-hole coupler

a) because it is more efficient

b) to increase coupling of the signal

c) to reduce spurious mode generation

d) to increase the bandwidth of the system

309. The smallest free-space wavelength that is just unable to propagate in the waveguide

a) cutoff wavelength

b) cutoff frequency

c) cutoff waveguide length

d) cutoff phase

310. It is the minimum frequency of waves that can propagate through the waveguide

a) cutoff frequency

b) cutoff wavelength

c) cutoff phase

d) cutoff waveguide length

311. A common application of magnetrons is in

a) Radar

b) Satellites

c) Two-way radio

d) TV sets

312. In waveguides, it is the velocity at which the wave changes phase

a) waveguide velocity

b) group velocity

c) phase velocity

d) total velocity

313. The maximum power that may be handled by a ferrite component is limited by the

a) curie temperature

b) saturation magnetization

c) line width

d) gyromagnetic resonance

314. In waveguides, it is the velocity at which the wave propagates

a) phase velocity

b) group velocity

c) total velocity

d) waveguide velocity

315. A PIN diode is

a) a metal semiconductor point-contact diode

b) a microwave mixer diode

c) often used as a microwave detector

d) suitable for use as a microwave switch

316. A common omnidirectional microwave antenna is the

a) horn

b) parabolic reflector

c) helical

d) bicone

317. The output of a helical antenna is

a) vertically polarized

b) horizontally polarized

c) circularly polarized

d) linearly polarized

318. For some applications, circular waveguides may be preferred to rectangular ones because of

a) the smaller the cross section needed at any frequency

b) lower attenuation

c) freedom from spurious modes

d) rotation of polarization

319. A helical antenna is made up of a coil and a

a) director

b) reflector

c) dipole

d) horn

320. In a klystron amplifier, velocity modulation of the electron beam is produced by the

a) collector

b) catcher cavity

c) cathode

d) buncher cavity

321. Increasing the diameter of a parabolic reflector causes which of the following:

a) decreased beamwidth

b) increased gain

c) none of the above

d) decreased beamwidth and increased gain

322. For low attenuation, the best transmission medium is

a) flexible waveguide

b) ridged waveguide

c) rectangular waveguide

d) coaxial line

323. Low-power Gunn diodes are replacing

a) Reflex klystron

b) TWTs

c) Magnetrons

d) Varactor diodes

324. One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their

a) noise figure increases

b) transmit time becomes too short

c) shunt capacitive reactances becomes too large

d) series inductance reactances becomes too small

325. A rectangular waveguide has a width of 1 inch and a height of 0.6 inch. Its cutoff frequency is

a) 2.54 GHz

b) 3.0 GHz

c) 5.9 GHz

d) 11.8 GHz

326. The TWT is sometimes preferred to the multicavity klystron amplifier, because the former

a) is more efficient

b) has a greater bandwidth

c) has a higher number of modes

d) produces higher output power

327. The most common cross section of a waveguide is a

a) square

b) circle

c) triangle

d) rectangle

328. The cavity magnetron uses strapping to

a) prevent mode jumping

b) prevent cathode back-heating

c) ensure bunching

d) improve the phase-focusing effect

329. Signal propagation in a waveguide is by

a) electrons

b) electric and magnetic fields

c) holes

d) air pressure

330. The dominant mode in most waveguides is

a) TE 0,1

b) TE 1,2

c) TM 0,1

d) TM 1,1

331. Periodic permanent-magnet focusing is used with TWTs to

a) allow pulsed operation

b) improve electron bunching

c) avoid the bulk of electromagnet

d) allow coupled-cavity operation at the highest frequencies

332. A popular microwave mixer diode is the

a) Gunn

b) Varactor

c) Hot carrier

d) IMPATT

333. A magnetron whose oscillating frequency is electronically adjustable over a wide range is called a

a) coaxial magnetron

b) dither-tune magnetron

c) frequency-agile magnetron

d) VTM

334. The main benefit of using microwave is

a) lower-cost equipment

b) sampler equipment

c) greater transmission distances

d) more spectrum space for signals

335. Which diode is a popular microwave oscillator?

a) IMPATT

b) Gunn

c) Varactor

d) Schottly

336. Which of the following is not a disadvantage of microwave?

a) higher cost equipment

b) line-of-sight transmission

c) conventional components are not usable

d) circuits are more difficult to analyze

337. Which of the following is a microwave frequency?

a) 1.7 MHz

b) 750 MHz

c) 0.98 MHz

d) 22 GHz

338. In a TWT, the electron beam, is density-modulated by a

a) Permanent magnet

b) Modulation transformer

c) Helix

d) Cavity resonator

339. Which of the following is not a common microwave application?

a) radar

b) mobile radio

c) telephone

d) spacecraft communications

340. Indicate the false statement. Transit time in microwave tubes will be reduced if

a) the electrodes are brought closer together

b) a higher node current is used

c) multiple or coaxial loads are used

d) the anode voltage is made larger

341. Coaxial cable is not widely used for long microwave transmission lines because of its

a) high loss

b) high lost

c) large size

d) excessive radiation

342. The main advantage of the TWT over a klystron for microwave amplification is

a) lower cost

b) smaller size

c) higher power

d) wider bandwidth

343. A magnetic field is used in the cavity magnetron to

a) prevent anode current in the absence of oscillations

b) ensure that the oscillations are pulsed

c) help in focusing the electron beam, thus preventing spreading

d) ensure that the electrons will orbit around the cathode

344. A waveguide has a cutoff frequency of 17 GHz. Which of the signals will not be passed by the waveguide?

a) 15 GHz

b) 18 GHz

c) 22 GHz

d) 25 GHz

345. When the electric field in a waveguide is perpendicular to the direction of wave propagation, the mode is said to be

a) vertical polarization

b) transverse electric

c) horizontal polarization

d) transverse magnetic

346. The TWT is sometimes preferred to the magnetron as a radar transmitter output tube because it is

a) capable of longer duty cycle

b) a more efficient amplifier

c) more broadband

d) less noisy

347. A magnetic field is introduced into a waveguide by a

a) probe

b) dipole

c) stripline

d) capacitor

348. A reflex klystron is used as a/n

a) amplifier

b) oscillator

c) mixer

d) frequency multiplier

349. Indicate the false statement: Manganese ferrite may be used as a

a) circulator

b) isolator

c) garnet

d) phase shifter

350. Indicate the false statement. Klystron amplifiers may use intermediate cavities to

a) prevent oscillations that occur in two-cavity klystron

b) increase the bandwidth of the device

c) improve the power gain

d) increase the efficiency of the klystron

Questions and Answers in Microwave Communications and Principles Series

Following is the list of multiple choice questions in this brand new series:

Complete List of MCQ in Communications Engineering per topic