This set of Avionics Multiple Choice Questions & Answers (MCQs) focuses 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
Explanation: 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
Explanation: 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
Explanation: 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 _______
Explanation: 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
Explanation: 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?
b) Electronic motors
c) Phase shifter
Explanation: 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?
b) Continuous wave
c) Low frequency
Explanation: 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
Explanation: 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
Explanation: A typical airborne active array contains 1000 to 2000 transmitting modules, each capable of transmitting 5 to 20 watts of power.
10. Which one of the following is common between AESA and PESA?
a) Number of transmitting modules
b) Number of frequencies that can be used
c) Power required by each transmitter
d) Electronic scanning capability
Explanation: One of the basic common features between the AESA and PESA is that both provide electronic scanning. This allows the use of narrow beams since the rate of scanning is very high.
11. AESA is more reliable than PESA.
Explanation: An AESA solves many of the reliability and maintainability problems due to TWT and power supply problems. 4 to 6% of the T/R module could fail without noticeable degradation in antenna performance.
12. AESA can alter its transmitting and receiving patterns.
Explanation: In AESA a new control variable is introduced. The gain of each Tx and Rx module can be controlled and hence the array radars can adaptively alter their transmit and receive antenna pattern to maximize system performance.
13. Which of the following can track multiple targets with ease?
d) Conical radar antenna
Explanation: AESA radars can produce multiple radar frequencies with multiple beams. This allows the radar to have faster scan rates and can track multiple targets with ease.
14. The possibility of one phased array radar to act as multiple radars is called as _______
d) interleaving radar modes
Explanation: Beam agility makes it possible for one phased array radar to act as multiple radars each with its own beam shape and scan pattern! This is referred to as interleaving radar modes. The same radar can be tracking for airborne threats using one beam shape and scan pattern while searching for ground targets using another beam shape and scan pattern.
15. In an aircraft ESA the beam shape and direction is controlled by _______
c) Ground controller
d) Cannot be controlled
Explanation: The beam shape and direction is controlled by an on-board computer which gives the necessary phase shift to the phase shifters to change the beam direction and shape.
Sanfoundry Global Education & Learning Series – Avionics.
To practice all areas of Avionics, here is complete set of 1000+ Multiple Choice Questions and Answers.