Online Questions and Answers Topic Outline
- MCQs in Basic Principles of Microwave Communications
- MCQs in Electro-Optics
- MCQs in Photonics
- MCQs in Optoelectronics
- MCQs in Electromagnetics
- MCQs in Avionics, Aerospace, Navigational and Military Applications
- MCQs in Medical Electronics
- MCQs in Cybernetics
- MCQs in Biometrics
MCQs in Microwave Communications and Principles Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part VI of the Series
251. Which of the following is not true: The radar cross section of a target
- a) depends on the frequency used
- b) may be reduced by special coating of the target
- c) depends on the aspect of a target, if this non-spherical
- d) is equal to the actual cross-sectional area for small targets
252. It is a general term applied to the reduction in signal strength at the input to a receiver
- a) fading
- b) attenuation
- c) absorption
- d) ghosting
253. Indicate which of the following cannot be followed by the word “waveguide”
- a) elliptical
- b) flexible
- c) coaxial
- d) ridged
254. If the ratio of the antenna diameter to the wavelength in a radar system is high, this will result in (indicate the false statement)
- a) large maximum range
- b) good target discrimination
- c) difficult target acquisition
- d) increased capture area
255. High-power TWTs are replacing what in microwave amplifiers?
- a) MESFETs
- b) Magnetrons
- c) Klystrons
- d) IMPATT diodes
256. The most widely used microwave antenna is a
- a) half-wave dipole
- b) quarter-wave probe
- c) single loop
- d) horn
257. Applies to propagation variables in the physical radio path which affect changes in path loss between the transmitter at one station and its normal receiver at the other station.
- a) ghosting
- b) absorption
- c) attenuation
- d) fading
258. If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of
- a) square root of 2
- b) 2
- c) 4
- d) 8
259. If the peak transmitted power in a radar system is increased by a factor of 15, the maximum range will be increased by a factor of
- a) 2
- b) 4
- c) 8
- d) 16
260. Varactor and step-recovery diodes are widely used in what type of circuit?
- a) amplifier
- b) oscillator
- c) frequency multiplier
- d) mixer
261. It is defined as line loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects.
- a) IRL
- b) FSL
- c) RSL
- d) Eb/No
262. For proper operation, a magnetron must be accompanied by a
- a) cavity resonator
- b) strong electric field
- c) permanent magnet
- d) high dc voltage
263. A police radar speed trap functions at a frequency of 1.024 GHz in direct line with your car. The reflected energy from your car is shifted 275 Hz in frequency. Calculate the speed in miles per hour?
- a) 60 mph
- b) 70 mph
- c) 80 mph
- d) 90 mph
264. It is the ratio of the wideband carrier to the wideband noise power
- a) carrier to noise ratio
- b) signal to noise ratio
- c) energy per bit per noise density ratio
- d) noise figure
265. What is the duty cycle of a radar pulse if the pulse width is 1µs, the pulse repetition rate is 900, and the average power is 18 W?
- a) 0.09 %
- b) 0.99 %
- c) 0.90 %
- d) 1.00 %
266. A microwave tube amplifier uses an axial magnetic field and a radial electric field. This is the
- a) reflex klystron
- b) coaxial magnetron
- c) traveling-wave magnetron
- d) CFA
267. Figure of merit used to indicate how much the signal-to-noise ratio deteriorates as a signal passes through a circuit or series of circuits
- a) noise factor
- b) signal to noise ratio
- c) carrier to noise ratio
- d) dynamic range
268. What is the peak power of a radar pulse if the pulse width is 1µs, the pulse repetition rate is 900, and the average power is 18 W?
- a) 10 kW
- b) 15 kW
- c) 20 kW
- d) 30 kW
269. The point where the antenna is mounted with respect to the parabolic reflector is called the
- a) focal point
- b) center
- c) locus
- d) tangent
270. The operating frequency of klystron and magnetrons is set by the
- a) cavity resonators
- b) DC supply voltage
- c) input signal frequency
- d) Number of cavities
271. Using a small reflector to beam waves to the larger parabolic reflector is known as
- a) focal feed
- b) horn feed
- c) cassegrain feed
- d) coax feed
272. If the noise figures and gains of each of the amplifiers in cascade is 3 dB and 10 dB respectively. What is the total noise figure?
- a) 2.12 dB
- b) 3.24 dB
- c) 1.24 dB
- d) 4.23 dB
273. One of the following is unlikely to be used as a pulsed device
- a) multicavity klystron
- b) BWO
- c) CFA
- d) TWT
274. Calculate the maximum ambiguous range for a radar system with PRT equal to 400µs.
- a) 13.8 mi
- b) 43.5 mi
- c) 16.4 mi
- d) 32.8 mi
275. When electromagnetic waves are propagated in a waveguide
- a) they travel along the broader walls of the guide
- b) they are reflected from the walls but do not travel along them
- c) they travel through the dielectric without the walls
- d) they travel along all four walls of the waveguide
276. What is the distance in nautical miles to a target if it takes 123 µs for a radar pulse to travel from the radar antenna to the target, back to the antenna, and be displayed on the PPI scope?
- a) 10 nmi
- b) 5 nmi
- c) 20 nmi
- d) 15 nmi
277. Waveguides are used mainly for microwave signals because
- a) they depend on straight-line propagation which applies to microwaves only
- b) losses would be too heavy at lower frequencies
- c) there are no generators powerful enough to excite them at lower frequencies
- d) they would be too bulky at lower frequencies
278. Calculate the coupling of a directional coupler that has 70 mW into the main guide and 0.35 mW out the secondary guide.
- a) 13 dB
- b) 23 dB
- c) 33 dB
- d) 10 dB
279. The wavelength of a wave in a waveguide
- a) is greater than in free space
- b) depends only on the waveguide dimensions and the free space wavelength
- c) is inversely proportional to the phase velocity
- d) is directly proportional to the group velocity
280. A rectangular waveguide is 1 cm by 2 cm. Calculate the cutoff frequency
- a) 3.5 GHz
- b) 15 GHz
- c) 7.5 GHz
- d) 4 GHz
281. The main difference between the operation of transmission liners and waveguides is that
- a) the latter is not distributed, like transmission lines
- b) the former can use stubs and quarter-wave transformers, unlike the latter
- c) transmission lines use the principal mode of propagation, and therefore do not suffer from low-frequency cut-off
- d) terms such as impedance matching and standing-wave ratio cannot be applied to waveguides
282. The useful power of the transmitter that is contained in the radiated pulses is termed as ______.
- a) rms power
- b) rated power
- c) peak power
- d) average power
283. In radars, echoes that are produced when the reflected beam is strong enough to make a second trip
- a) double range echoes
- b) double frequencies echoes
- c) second return echoes
- d) second time around echoes
284. Indicate the false statement. Compared with equivalent transmission lines, 3 GHz waveguides
- a) are less lossy
- b) can carry higher powers
- c) are less bulky
- d) have lower attenuation
285. The range beyond which targets appear as second return echoes is called
- a) maximum range
- b) maximum unambiguous range
- c) maximum usable range
- d) any of these
286. When a particular mode is excited in a waveguide, there appears an extra electric component, in the direction of propagation. The resulting mode is
- a) transverse electric
- b) transverse magnetic
- c) longitudinal
- d) transverse-electromagnetic
287. In radars, echoes that arrive after the transmission of the next pulse are called _____.
- a) second return echoes
- b) second time around echoes
- c) multiple time around echoes
- d) any of these
288. When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is
- a) the same as the free space
- b) the same as the wavelength perpendicular to the wall
- c) shortened because of the Doppler effect
- d) greater than in the actual direction of propagation
289. A radar mile is equivalent to
- a) 2000 mi
- b) 2000 m
- c) 2000 yd
- d) 2000 km
290. As a result of reflections from a plane conducting wall, electromagnetic waves acquire an apparent velocity of light in space
- a) velocity of propagation
- b) normal velocity
- c) group velocity
- d) phase velocity
291. In radars, the time between pulses is called ______.
- a) rest time
- b) duration time
- c) delay time
- d) propagation time
292. Indicate the false statement. When the free-space wavelength of a signal equals the cutoff wavelength of the guide
- a) the group velocity of the signal becomes zero
- b) the phase velocity of the signal becomes infinite
- c) the characteristic impedance of the guide becomes infinite
- d) the wavelength within the waveguide becomes infinite
293. In radars, the duration of the pulse is
- a) duty cycle
- b) pulse width
- c) pulse amplitude
- d) pulse cycle
294. A signal propagated in a waveguide has a full wave electric intensity change between two further walls, and no component of the electric field in the direction of propagation. The mode is
- a) TE11
- b) TE10
- c) TM22
- d) TE20
295. In radars, the number of the pulses transmitted per second is called
- a) pulse repetition frequency
- b) pulse repetition time
- c) pulse repetition phase
- d) pulse number of repetition
296. Which of the following is incorrect? The dominant mode of propagation is preferred with rectangular waveguides because
- a) it leads to the smallest waveguide dimensions
- b) the resulting impedance can be matched directly to coaxial lines
- c) it is easier to excite than other modes
- d) propagation of it without any spurious generation can be ensured
297. It is a mean of employing radio waves to detect and locate objects such as aircraft, ships and land masses.
- a) detectors
- b) radars
- c) repeaters
- d) beacons
298. A choke flange may be used to couple two waveguides
- a) to help the alignment of the waveguides
- b) because it is simpler than any other join
- c) to compensate for discontinuities at the join
- d) to increase the bandwidth of the system
299. The resonant frequency of a cavity may be varied by changing any of these parameters except:
- a) cavity volume
- b) cavity inductance
- c) cavity capacitance
- d) cavity resistance
300. In order to couple two generators to a waveguide system without coupling them to each other, which could not be use?
- a) rat-race
- b) E-plane T
- c) hybrid ring
- d) magic T
Post a Comment