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# MCQ in Microwave Communications Part 5 | ECE Board Exam

This is the Multiples Choice Questions Part 5 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 5 of the Series

201. IF repeaters are also called

Solution:

202. It is the difference between the nominal output power of a transmitter and the minimum input power required by a receiver

a) RSL

b) IRL

c) system gain

d) FSL

Solution:

203. A phenomenon whereby the frequency of a reflected of a reflected signal is shifted if there is relative motion between the source and reflecting object.

a) Doppler effect

b) Hall effect

c) Marconi effect

d) Maxwell effect

Solution:

204. A ferrite is

a) a nonconductor with magnetic properties

b) an intermetallic compound with particularly good conductivity

c) an insulator which heavily attenuates magnetic fields

d) a microwave semiconductor invented by Faraday

Solution:

205. The primary purpose of the helix in a traveling-wave tube is to

a) prevent the electron beam from spreading in the long tube

b) reduce the axial velocity of the RF field

d) reduce the noise figure

Solution:

206. The attenuator is used in the travelling-wave tube to

a) help bunching

b) prevent oscillations

c) prevent saturation

d) increase the gain

Solution:

207. A magnetron is used only as

a) amplifier

b) oscillator

c) mixer

d) frequency multiplier

Solution:

208. A backward-wave oscillator is based on the

a) rising-sun magnetron

b) crossed-field amplifier

c) coaxial magnetron

d) traveling-wave tube

Solution:

209. Stripline and microstrip transmission lines are usually made with

a) coax

b) parallel lines

c) twisted pair

d) PCBs

Solution:

210. Which of the following is not a microwave tube?

a) Traveling-wave tube

b) Cathode-ray tube

c) Klystron

d) Magnetron

Solution:

211. Indicate which is not true. Compared with other types of radar, phased array radar has the following advantages

a) very fast scanning

b) ability to track and scan simultaneously

c) circuit simplicity

d) ability to track many targets simultaneously

Solution:

212. Given the frequency and dimensions of 5 GHz and 7 cm by 9 cm respectively, the beam of the pyramidal horn is about ______.

a) 27 degrees

b) 53 degrees

c) 60 degrees

d) 80 degrees

Solution:

213. The diameter of a parabolic reflector should be at least how many wavelengths at the operating frequency?

a) 1

b) 2

c) 5

d) 10

Solution:

214. A type of microwave repeater where the received RF carrier is down-converted to an IF frequency, amplified filtered and further demodulated to baseband.

a) RF repeater

b) IF repeater

c) baseband repeater

Solution:

215. In order to reduce cross-sectional dimensions, the waveguide to use is

a) circular

b) ridged

c) rectangular

d) flexible

Solution:

216. Indicate which one of the following applications or advantages of radar beacons is false:

a) target identification

c) very significant extension of the maximum range

d) more accurate tracking enemy targets

Solution:

217. Refers to more than one transmission path or method of transmission available between transmitter and a receiver.

a) diversity

b) polarization

c) efficiency

d) accuracy

Solution:

218. A solution to the โblind speedโ problem is to

a) change the Doppler frequency

b) vary the RF

c) use monopulse

d) use MTI

Solution:

219. A direct path that exist between the transmit and receive antennas

a) LOS

b) direct waves

c) space waves

d) terrestrial waves

Solution:

220. The function of the quartz delay line in an MTI radar is to

a) help in subtracting a complete scan from the previous scan

b) match the phase of the coho and the stalo

c) match the phase of the coho and the output oscillator

d) delay a sweep so that the next sweep can be subtracted from it

Solution:

221. Type of diversity where it modulates two different RF carrier frequencies with the same IF intelligence, then transmitting both RF signals to a given destination.

a) polarization diversity

c) space diversity

d) frequency diversity

Solution:

222. The coho in MTI radar operates at the

a) intermediate frequency

b) transmitted frequency

d) pulse operation frequency

Solution:

223. Which type of diode does not ordinarily operate with reverse bias?

a) Varactor

b) IMPATT

c) Snapp-off

d) Tunnel

Solution:

224. What happens when a horn antenna is made longer?

a) gain increases

b) beam width decreases

c) bandwidth increases

d) bandwidth decreases

Solution:

225. A pyramidal horn used at 5 GHz has an aperture that is 7 cm by 9 cm. The gain is about

a) 10.5 dB

b) 11.1 dB

c) 22.6 dB

d) 35.8 dB

Solution:

226. Type of diversity where the output of the transmitter is fed to two or more antennas that are physically separated by an appreciable wavelengths

b) wavelength diversity

c) space diversity

d) hybrid diversity

Solution:

227. The Doppler effect is used in (indicate the false statement)

a) moving-target plotting on the PPI

b) the MTI system

Solution:

228. A type of diversity where a single RF carrier is propagated with two different electromagnetic polarization.

a) space diversity

b) wavelength diversity

c) polarization diversity

d) hybrid diversity

Solution:

229. The A scope displays

a) the target position and range

b) the target range, but not position

c) the target position, but not range

d) neither range nor position, but only velocity

Solution:

230. The glass tube of a TWT may be coated with aquadag to

a) help focusing

b) provide attenuation

c) improve bunching

d) increase gain

Solution:

231. Type of diversity which consists of a standard frequency diversity path where the two transmitter/receiver pair at one end of the path are separated from each other and connected to different antennas that are vertically separated as in space diversity

b) wavelength diversity

c) space diversity

d) hybrid diversity

Solution:

a) it does not give the target velocity

b) it does not give the target range

c) a transponder is required at the target

d) it does not give the target position

Solution:

233. The combination of the frequency, space, polarization and receiver diversity into one system

a) hybrid diversity

c) space diversity

d) wavelength diversity

Solution:

234. If the target cross section is changing, the best system for accurate tracking in

a) lobe switching

b) sequential lobing

c) conical switching

d) monopulse

Solution:

235. The multicavity klystron

a) is not good low-level amplifier because of noise

b) has a high repeller voltage to ensure a rapid transmit time

c) is not suitable for pulse operation

d) needs a long transmit time through the buncher cavity to ensure current modulation

Solution:

236. An arrangement that avoids a service interruption during periods of deep fades or equipment failures.

a) service switching arrangement

b) protection switching arrangement

c) interruption switching arrangement

d) equipment switching arrangement

Solution:

237. A type of attenuator where attenuation is accomplished by insertion of a thin card of resistive material through a slot in the top of a waveguide

a) flap attenuator

b) vane attenuator

c) slot attenuator

d) directional coupler

Solution:

238. After a target has been acquired, the best scanning system for tracking is

a) nodding

b) spiral

c) conical

d) helical

Solution:

239. A duplexer is used

a) to couple two different antennas to a transmitter without mutual interference

b) to allow the one antenna to be used for reception or transmission without mutual interference

c) to prevent interference between two antennas when they are connected to a receiver

d) to increase the speed of pulses in pulsed radar

Solution:

240. Type of protection switching arrangement where each working radio channel has a dedicated backup or spare channel

a) hot swap

b) hot backup

c) hot standby

d) hot diversity

Solution:

241. If a return echo arrives after the allocated pulse interval,

a) it will interfere with the operation of the transmitter

c) it will not be received

d) the target will appear closer than it really is

Solution:

242. Points in the microwave system baseband signals either originate or terminate

a) terminator

b) terminal stations

c) terminating equipment

d) terminal equipment

Solution:

243. A half wavelength, closed section of a waveguide that acts as a parallel resonant circuit is known as _____.

a) half-wave section

b) cavity resonator

c) LCR circuit

d) directional couple

Solution:

244. Decreasing the volume of a cavity causes its resonant frequency to

a) increase

b) decrease

c) remains the same

d) drop to zero

Solution:

245. The IF bandwidth of a radar receiver is inversely proportional to the

a) pulse width

b) pulse repetition frequency

c) pulse interval

d) the target will appear closer than it really is

Solution:

246. Which of the following devices are not being used in microwave power amplifier?

a) klystron tubes

b) traveling wave tubes

c) IMPATT

d) magnetron

Solution:

247. Which is not true? A high PRF will

a) make the returned echoes easier to distinguish from noise

b) make the target tracking easier with conical scanning

c) increase the maximum range

d) have no effect on the range resolution

Solution:

248. It is a unidirectional device often made up of ferrite material used in conjunction with a channel-combining network to prevent the output from interfering with the output of another transmitter

a) circulator

b) magic tee

c) isolator

d) rat race

Solution:

249. Which is not true about the following: Flat-topped rectangular pulses must be transmitted in radar to

a) allow a good minimum range

b) make the returned echoes easier to distinguish from the noise

c) prevent frequency changes in the magnetron

d) allow accurate range measurements

Solution:

250. The power that leaks out of the back and sides of the transmit antenna interfering with the signal entering with the signal entering the input of a nearby receive antenna.

a) ringaround

d) turnaround

Solution:

#### Questions and Answers in Microwave Communications and Principles Series

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

MCQ in Microwave Communications
PART 1: MCQ from Number 1 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: PART 4
PART 5: MCQ from Number 201 โ 250                 Answer key: PART 5
PART 6: MCQ from Number 251 โ 300                 Answer key: PART 6
PART 7: MCQ from Number 301 โ 350                 Answer key: PART 7
PART 8: MCQ from Number 351 โ 400                 Answer key: PART 8
PART 9: MCQs from Number 401 โ 450                 Answer key: PART 9
PART 10: MCQs from Number 451 โ 500                 Answer key: PART 10

### Complete List of MCQ in Communications Engineering per topic

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