Avionics Multiple Choice Questions on “Electronic Scanned Array Radar”.
1. What is the fundamental limitation of the radar that is overcome by Electronic scanned array radars?
a) More clarity
b) Situation awareness
c) Better range
d) Less noise
Answer: b
Clarification: The fundamental limitation in military radars is situation awareness. This limitation is overcome by the electronically scanned array which has a very high rate of scanning.
2. How is the radar beam moved in the ESA?
a) Phase shift
b) Mechanical gimbal
c) Mechanical servos
d) Hydraulics
Answer: a
Clarification: In ESA, the antenna’s beam is moved electronically by setting the phase angles of phase shifters located at each radiating element to provide a linear phase taper across the array surface.
3. Which of the following determines the direction of the antenna beam in ESA?
a) Physical direction of antenna
b) Direction of aircraft nose
c) Slope of the phase taper
d) Mechanical gimbal
Answer: c
Clarification: The ESA controls the beam by phase shifters. The slope of the phase taper determines the direction in which the antenna beam will be pointed.
4. The ESA radar beam can be repositioned in a few _______
a) Microseconds
b) Nanoseconds
c) Milliseconds
d) Seconds
Answer: a
Clarification: Since the antenna’s phase shifter settings can be changed in a few microseconds, an ESA’s beam can be repositioned almost instantly.
5. The ESA is more _________ since it has no moving parts.
a) Prone to failure
b) Powerful
c) Reliable
d) Accurate
Answer: c
Clarification: The antenna reliability is dramatically improved in an ESA since there is no moving parts present. The antennas face one direction but the radar beam can be steered electronically to a very wide angle.
6. Which of the following are present in an ESA?
a) Gimbals
b) Electronic motors
c) Phase shifter
d) Potentiometer
Answer: c
Clarification: The ESA has no mechanical moving parts, such as antenna gimbals, potentiometers, rotary joints, or hydraulic/electronic motors. It uses phase shifters to electronically steer the beam.
7. Both AESA and PESA are ________ radars?
a) Pulse
b) Continuous wave
c) Low frequency
d) Analog
Answer: a
Clarification: Both AESA and PESA that are currently in use are pulse radars. Its basic principle is that shorts bursts of radio pulse are emitted which reflect off a target and the reflected pulse gives the information about the object.
8. Which of the following is false with respect to PESA?
a) PESA can only have one main beam and one transmit power source
b) All elements combine to a single receiver. Each element steers the beam through phase shifters
c) Because it uses a, multiple frequencies, it is less susceptible to enemy jammers
d) PESA is more technically simple
Answer: c
Clarification: In a PESA only one transmitter drives the whole antenna and hence only one frequency can be achieved at a time. This allows it to be more susceptible to jammers.
9. What is the number of transmitting modules in a common AESA?
a) 20 to 50
b) 1000 to 2000
c) 150 to 200
d) 1