This set of Radar Multiple Choice Questions & Answers (MCQs) focuses on “Types of Complex Targets”.

1. Which out of the following is not an example of a complex target?
a) Aircraft
b) Buildings
c) Fabricated structures
d) Cone

Explanation: Aircraft, buildings, fabricated structures are examples of complex targets however cone is a simple target. It’s easier to tell them apart based on their design complexity and their dimension variations. As for complex targets, it has a complex design compared to variations.

2. Depending upon the viewing aspect and frequency, the variability results due to multiple individual scatterers constituting the target.
a) True
b) False

Explanation: It is true that depending upon the viewing aspect, the multiple scatterers helps in identifying the target since each and every individual scattered wave once get reflected back from the complex structure of a target such as an airplane or a ship helps in rejuvenating the real shape and structure of the object.

3. In World War II, which out of the following band designation was used while operating radar in an aircraft?
a) L
b) S
c) C
d) X

Explanation: During World War II the aircraft were mounted on a turntable in surroundings free from other reflecting objects and was illuminated by a radar operating at 3 GHz (S band). The aircraft’s propellers were running during the measurement and produced modulation of the order of 1 to 2 kHz.

4. The cross section of an aircraft’s radar antenna is less if the radar antenna is in the nose and pointing in the direction of the viewing target.
a) True
b) False

Explanation: The cross section of an aircraft’s radar antenna is large if the radar antenna is in the noise and pointing in the direction of the viewing target, plus at angles a few degrees off the nose, the cross section generally decreases until echoes from the leading edge of the wing become important.

5. What happens if the wing of an aircraft is viewed from below or slightly above and perpendicular to its trailing edge?
a) Variation in backscatter occurs
b) The cross section appears larger
c) A travelling wave is induced
d) Scattering characteristics can be obtained

Explanation: If the wing is viewed from slightly below or above, a traveling wave can be induced and there can be a radar echo due to reflection from the trailing edge of the wing. This traveling wave echo can be larger for vertical polarization than horizontal.

6. What is the most realistic method for obtaining the radar cross section of an aircraft?
a) Measure the actual aircraft in flight
b) Measure the aircraft’s body parts before assembling
c) Measure each and every body dimensions before flight
d) Dismantle and measure it

Explanation: The radar cross section of an aircraft can be measured realistically when the aircraft is in the middle of flight. The dynamic radar cross section measurement was able to measure the backscatter signals from aircraft L, S, C and X bands with horizontal or vertical linear polarization, circular polarization as well as cross polarization on receive.

7. Airborne synthetic aperture radar is an unusual technique for obtaining the scattering characteristics of an aircraft which was utilized by _______
a) Trimble
b) Metratek
c) Actsoft
d) Masternaut

Explanation: The method for obtaining scattering characteristics of an aircraft was utilized by Metratek, Inc. of Reston, Virginia. Airborne synthetic aperture radar is a high resolution multi frequency imaging radar mounted on the tail of an A-3 aircraft to provide 300° coverage.

8. In ships during low grazing angles near zero degrees, how can we express the median (50th percentile) value of the radar cross section?
a) σ = 52 f D3/2
b) σ = 52 f1/2 D1/2
c) σ = 52 f3/2 D1/2
d) σ = 52 f1/2 D3/2

Explanation: The median value can be expressed by the empirical relationship σ = 52 f1/2 D3/2 where σ is the radar cross section, f is the radar frequency and D is the ship’s displacement. The value of cross section was the average taken about the port and starboard bow and quarter aspects of a number of ships.

9. The values of ship cross sections at zero grazing angle compared to cross sections at higher grazing angles are ________
a) zero
b) same
c) higher
d) lesser

Explanation: The values of ship cross sections at zero grazing angle are much higher than the cross sections at higher grazing angles. At zero degrees a ship’s super structure presents many vertical surfaces and corner reflectors, both of which have large backscatter echoes.

10. Which theorem for the radars cross section of a ship says that the cross section in square meters can be approximated by the ship’s displacement in tons?
a) Target decomposition theorem
b) Range ambiguity theorem
c) Folk theorem
d) Chinese remainder theorem

Explanation: A folk theorem for the radar cross section of a ship is that the cross section in square meters can be approximated by the ship’s displacement in tons. For example, a 10,000 ton ship might be said to have a radar cross section of the order 10,000 m2.

Sanfoundry Global Education & Learning Series – Radar.

To practice all areas of Radar, here is complete set of Multiple Choice Questions and Answers.

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