Antennas Questions and Answers – Binomial Array

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This set of Antennas Multiple Choice Questions & Answers (MCQs) focuses on “Binomial Array”.

1. Which of the following array is used to synthesize pattern without side lobes?
a) Binomial array
b) Linear array
c) End-fire array
d) Chebyshev array
View Answer

Answer: a
Explanation: Binomial array is used to synthesize patterns without side lobes. In Chebyshev there are side-lobes present below the major beam level. The excitation amplitudes of the binomial array follow a Pascal’s triangle.

2. The excitation amplitudes of the binomial array follow ____________
a) Pascal’s triangle
b) Bermuda triangle
c) Right angled triangle
d) Natural squares
View Answer

Answer: a
Explanation: The excitation amplitudes of the binomial array follow a Pascal’s triangle.

   1
  1 1
 1 2 1  
1 3 3 1

The array factor AF = (1-z)N-1 and N is number of elements.

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3. Which of following is the disadvantage of the binomial array?
a) It has low amplitude variations
b) It has high range of amplitude variations
c) It has a high HPBW
d) It has low HPBW
View Answer

Answer: a
Explanation: Binomial array follows a Pascal’s triangle type of amplitude variations. So there are high variations in the amplitudes. Binomial array has high HPBW and hence more wide beams are present.

4. Binomial array has high HPBW compared to Dolph-chebychev.
a) True
b) False
View Answer

Answer: a
Explanation: Binomial array has wide beams and so it has high HPBW. Its HPBW is high compared to Dolph-Chebyshev array. Binomial array is used to synthesize patterns without side lobes.
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5. Which of the following can be the excitation amplitude of binomial array with 4 elements?
a) 1 3 3 1
b) 1 2 3 1
c) 2 1 1 2
d) 1 4 6 4 1
View Answer

Answer: a
Explanation: The excitation amplitudes of the binomial array follow a Pascal’s triangle.

     1	            N=1
    1 1     	    N=2 
   1 2 1   	    N=3  
  1 3 3 1	    N=4

The array factor AF = (1+z)N-1 and N is number of elements.

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6. Dolph- Chebyshev becomes a Binomial array when there are no side lobes.
a) True
b) False
View Answer

Answer: a
Explanation: Binomial array is used to synthesize patterns without side lobes. Dolph- chebyshev method is used to design array with desired side lobes. When the side lobe of the Dolph drops to -∞ dB, it behaves like a binomial array.

7. What will be the array factor in polynomial form for the 3 element binomial array if Z=e^(-iᴪ)?
a) 1+2z+z2
b) 1+3z+3z2+z3
c) 1+2z+3z2+z3
d) 1+3z+z2
View Answer

Answer: a
Explanation: The array factor AF = (1+z)N-1 and N is number of elements.
AF = (1+z)3-1 = (1+z)2 = 1+2z+z2
Binomial array follows the Pascal’s triangle coefficients

     1	            N=1
    1 1     	    N=2 
   1 2 1   	    N=3  
  1 3 3 1	    N=4.
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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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