Question 1
In which of the following a single radiator source is used to feed antenna with different phase shifts?
A. Phased array
B. FMCW radar
C. Monopulse radar
D. CW radar
View Answer
Answer: A
Explanation: In phased array radar a single radiator is used to feed antenna with different phase shifts and thus the desired beam width is obtained. The beam of phased array radar is a synthesis of the multiple antennas used at different phase shifts. In FMCW, Monopulse, CW radar multiple antennas are not usually used at different phase shifts.
Question 2
In which of the following principle is used in the phased array radar?
A. Interference
B. Diffraction
C. Reflection
D. Refraction
View Answer
Answer: A
Explanation: In phased array radar a single radiator is used to feed antenna array with different phase shifts. When the signals are in-phase the superposition occurs and out of phase cancellation takes place. Thus it is able to steer the beam to required direction.
Question 3
Electronic scanning is more advantageous compared to mechanical scanning
A. True
B. False
View Answer
Answer: A
Explanation: Electronic scanning is flexible and also requires low maintenance. Electronic scanning is composed of phase shifters, electrical circuits that steer the beam. So Electronic Scanning is better compared to mechanical scanning.
Question 4
In Frequency scanning, the phase of all radiators is constant for the frequency tuned at that instant.
A. True
B. False
View Answer
Answer: A
Explanation: In frequency scanning, for one frequency all radiators will be in phase. As the frequency is changed then a corresponding phase shift occurs and the beam is scanned.
Question 5
In which of the following type of scanning a heterodyne is used?
A. IF Scanning
B. Frequency scanning
C. Phase scanning
D. Digital beam-forming
View Answer
Question 6
In which of the following scanning the phase of the radiator is constant at one frequency?
A. Phase scanning
B. Frequency scanning
C. Both Phase and frequency scanning
D. Neither Frequency nor Phase scanning
View Answer
Answer: B
Explanation: In frequency scanning, for one frequency all radiators will be in phase. As the frequency is changed then a corresponding phase shift occurs and the beam is scanned. In phase scanning the phase shifters are used and radiators have different phases.
Question 7
Which of the following is mainly used in electronic scanning?
A. Phase shifters
B. Amplifiers
C. Repeaters
D. Limiters
View Answer
Answer: A
Explanation: Electronic scanning is flexible and also requires low maintenance. Electronic scanning is composed of phase shifters, electrical circuits that steer the beam. For the beam to change its direction, the phase of the radiators has to be changed and so the phase shifters used.
Question 8
In which of the following scanning the phase of the radiators varies incrementally for scan?
A. Phase scanning
B. Frequency scanning
C. IF scanning
D. Beam forming
View Answer
Answer: A
Explanation: In phased array radar a single radiator is used to feed antenna with different phase shifts and thus the desired beam width is obtained. In phase scanning the phase shifters are used and radiators have different phases.
Question 9
Phase array with lens array come under which feeding system?
A. Optical-feed system
B. Constrained feed system
C. Sub array feed
D. Phase shifter
View Answer
Answer: A
Explanation: Phased array with lens or reflector arrays comes under the optical feed system. Proper aperture illumination is obtained by the optical feed system. In constrained the power is divided into many elements under different steps.
Question 10
Which of the following statement is true?
A. Lens array has different input and output radiators while same radiator is used for reflector array
B. There is no surface matching required for the lens array
C. In lens and reflect array same radiator is used for input and output
D. Lens and reflect array belong to constrained feed systems
View Answer
Answer: A
Explanation: In Lens array, different input and output radiators are used and hence there two surface matching is required. In reflect array the same radiator is used to radiate and collect.Phased array with lens or reflector arrays comes under the optical feed system.
Question 11
In which of the following feed system, the power division among elements on aperture is done in several steps?
A. Constrained feed systems
B. Optical feed systems
C. Lens array
D. Reflect array
View Answer
Answer: A
Explanation: The power is divided into many elements under different steps in constrained feed systems. Phased array antennas with lens or reflector arrays belong to the optical feed system. Proper aperture illumination is obtained through the optical feed system and systems power is divided in one step.
Question 12
Which of the following series feed has same bandwidth similar to parallel feed network?
A. End fed array
B. Center fed array
C. Both end fed and Center fed array
D. Neither End fed nor center fed array
View Answer
Answer: B
Explanation: The Center fed array in the series feed network has same bandwidth as the parallel feed networks. The end fed array has several bandwidth restrictions.
Question 13
In which of the following the feed is provided at the end of the array?
A. Series end fed
B. Series center fed
C. Parallel feed
D. Optical feed systems
View Answer
Answer: A
Explanation: In series end fed, the radiator is placed at the end of the array and its electrical path length depends on the frequency. In center fed, radiator is provided at the center of the array and has bandwidth similar to the parallel feed network. In parallel feed, a number of radiators are combined into sub-arrays and then to elements in series or center fed.
Question 14
In which of the following radiators are combined into sub-arrays and then fed to elements in end or center fed?
A. Parallel feed
B. Series feed
C. Optical feed system
D. Series end feed
View Answer
Answer: A
Explanation: In parallel feed, a number of radiators are combined into sub-arrays and then to elements in series or center fed. In series end fed, the radiator is placed at the end of the array and its electrical path length depends on the frequency.In optical feed systems power is divided in one step.
Question 15
In which of the following the power is divided in single step among the elements?
A. Optical feed system
B. Constrained feed system
C. Parallel feed system
D. Sub-array
View Answer
Answer: A
Explanation: Proper aperture illumination is obtained by the optical feed system. In constrained the power is divided into many elements under different steps. In optical feed systems power is divided in one step. In parallel feed, a number of radiators are combined into sub-arrays and then to elements in series or center fed.
Question 16
The power divider used to connect array elements to single port is called _____
A. array feed
B. phase shifter
C. frequency shifter
D. repeater
View Answer
Answer: A
Explanation: The power divider used to connect array elements to single port is called array feed. Array feeds are classified into three types: Constrained feeds, Optical feed/ space feed, parallel plate feed.
Question 17
In which of the following feed techniques the reflect array used particularly?
A. Space feed
B. Constrained feed
C. Parallel plate feed
D. Sub array
View Answer
Answer: A
Explanation: In space feed, the energy is distributed to the lens array in a manner analogous to point feed illuminating a reflect antenna. In constrained the power is divided into many elements under different steps. In optical feed systems power is divided in one step. Parallel plate feed uses microwave structure principles and provides efficient power division.
Question 18
A folded pillbox antenna is used in which of the following feeding system?
A. Parallel plate feed
B. Space feed
C. Optical feed system
D. Constrained feed system
View Answer
Question 19
Parallel plate feed is a cross of constrained and space feed.
A. True
B. False
View Answer
Question 20
In which of the following the noise interference is detected and is suppressed further?
A. Adaptive arrays
B. Phased array
C. Planar array
D. Sub-array
View Answer
Question 21
The noise detection and suppression is possible with adaptive arrays.
A. True
B. False
View Answer
Question 22
Adaptive arrays provide best results compared to switching beams under more interference.
A. True
B. False
View Answer
Question 23
In which of the following the nulls are introduced effectively when different other users interferes the desired user?
A. Adaptive array
B. Switching beam
C. Phased array
D. Sub-array
View Answer
Question 24
_________ is used to guide the beam in desired direction and place nulls in unwanted direction/interference.
A. Adaptive array
B. Switching beam
C. Phased array
D. Pulse radar
View Answer
Question 25
Which of the following statements is false?
A. The intra cellular handoffs are less in adaptive array compared to switching beams
B. Noise interference cannot be detected in adaptive arrays effectively compared to switching beams
C. Advanced digital signal processors are used in adaptive arrays
D. Algorithms used in adaptive array is more complex than switching beams
View Answer
Question 26
In which of the following is not a benefit of the adaptive array technology?
A. Co-channel interference reduction
B. Reduction in multipath interference
C. Increase in multipath interference
D. Reduction in handoffs
View Answer
Question 27
In which of the following a real time adaptive signal processor is used?
A. Adaptive array
B. Phased array
C. Pulse radar
D. CW radar
View Answer
Question 28
Antenna synthesis is inverse process to antenna analysis.
A. True
B. False
View Answer
Answer: B
Explanation: Schelkunoff is one of the methods of antenna synthesis. Antenna synthesis determines the distribution of input or output sources from the obtained radiation pattern. Antenna analysis is determining the radiation pattern for the given input distribution.
Answer: A
Explanation: Antenna synthesis determines the distribution of input or output sources from the obtained radiation pattern. Antenna analysis is determining the radiation pattern for the given input distribution.
Question 29
In which of the following methods nulls are introduced in the desired direction of pattern?
A. Schelkunoff
B. Taylor
C. Woodward
D. Fourier
View Answer
Answer: A
Explanation: In Schelkunoff method, pattern is produced with null in specified directions. Woodward method is suited for beam shaping and Fourier is used when the complete pattern and excitation distributions locations are given. Taylor series have a constant inner minor lobes level and decreasing lobes for other.
Question 30
In which of the following method is popularly used for beam shaping in antenna synthesis?
A. Woodward
B. Schelkunoff
C. Fourier
D. Taylor
View Answer
Answer: A
Explanation: Woodward method is suited for beam shaping and the complete pattern and excitation distributions locations are given by the Fourier method. The nulls in specified pattern are produced by the Schelkunoff method. The Taylor synthesis has a constant inner minor lobes level.
Question 31
In which of the following synthesis method have a constant inner minor lobe level and remaining one decreasing gradually?
A. Woodward
B. Schelkunoff
C. Fourier
D. Taylor
View Answer
Answer: D
Explanation: Taylor synthesis has a constant inner minor lobes level and gradually decreasing lobes for other. Nulls are produced in a specified direction for the pattern using Schelkunoff method. The Woodward method is used for beam shaping in antenna synthesis while Fourier is used when the complete pattern and excitation distributions locations are given.
Question 32
Antenna synthesis is analogous to _________.
A. Antenna array
B. Antenna analysis
C. Antenna radiation
D. Schelkunoff synthesis
View Answer
Answer: B
Explanation: Schelkunoff is one of the methods of antenna synthesis. Antenna synthesis determines the distribution of input or output sources from the obtained radiation pattern. Antenna analysis is determining the radiation pattern for the given input distribution.
Question 33
In which of the following is not a technique of antenna synthesis?
A. Woodward
B. Schelkunoff
C. Fourier
D. Thinning
View Answer
Answer: D
Explanation: Thinning is a process to reduce the array elements with degrading the performance. Woodward-Lawson, Schelkunoff, Fourier, Taylor are techniques of antenna synthesis.Antenna synthesis determines the distribution of input or output sources from the obtained radiation pattern.
Question 34
In which of the following method is used for antenna design with no side lobes?
A. Binomial array
B. Dolph Chebyshev
C. Schelkunoff
D. Woodward
View Answer
Answer: A
Explanation: Dolph Chebyshev is a special case (at no side lobes) of Binomial array. Dolph Chebyshev is used to design array at desired side lobes. In Schelkunoff method, pattern is produced with null in specified directions. Woodward method is suited for beam shaping.
Question 35
Which of the following is the key feature of the Chebyshev array?
A. Have constant side lobes and elements are placed uniformly
B. Have varying side lobes and elements are placed uniformly
C. Minor lobes are present at |x| > 1
D. Major lobes are present at |x| < 1
View Answer
Answer: A
Explanation: Chebyshev array exhibits the properties of the Chebyshev polynomial having constant amplitude 1-≤x≤1. Minor lobes are present at |x| < 1 andMajor lobes are present at |x| > 1.
Question 36
In Chebyshev array, its array factor is approximated to Chebyshev polynomial.
A. True
B. False
View Answer
Answer: A
Explanation: One of the properties exhibited by the Chebyshev array is having a constant amplitude range of 1-≤x≤1. Its array factor is approximated to Chebyshev polynomial. This array has constant side lobes and elements are placed uniformly.
Question 37
________ is used to obtain array with any desired side lobe level.
A. Chebyshev
B. Schelkunoff
C. Woodward-Lawson
D. Binomial
View Answer
Answer: A
Explanation: Chebyshev technique is used to obtain array with any desired side lobe level. In Schelkunoff method, pattern is produced with null in specified directions. Woodward method is suited for beam shaping. Binomial array is used when no side lobes are desired.