# Antennas Questions and Answers – Adaptive Array – Dolph Pattern Method

This set of Antennas Multiple Choice Questions & Answers (MCQs) focuses on “Adaptive Array – Dolph Pattern Method”.

1. Which of the following a method proposed to design array with any side lobes?
a) Dolph-Chebyshev
b) Binomial array
c) Taylor

Explanation: Dolph- chebyshev method is used to design array with desired side lobes. It uses the approximation of the Chebyshev polynomials. Binomial array is used to synthesis the patterns without side lobes. Taylor and broad-side array have side lobes.

2. Dolph pattern uses which of the following polynomial approximation?
a) Chebyshev
b) Binomial
c) Pascal’s
d) Taylor

Explanation: An array with desired side lobes can be designed by using the Dolph-chebyshev method. This method uses the approximation of the Chebyshev polynomials. Binomial array uses the Pascal’s triangle for amplitude excitations.

3. What should be the side lobe level to make Dolph Chebyshev to binomial array?
a) -∞ dB
b) 0 dB
c) 1 dB
d) 10dB

Explanation: Dolph –Chebyshev will become binomial array when there are no any side lobes.
So side lobes a =0
Side lobe level = major lobe level / minor lobe max =0
In dB = 20 log (1/a) = -∞ dB.

4. Which of the following represents the chebyshev recursive formula?
a) Tm(z) = 2zTm-1(z) – Tm-2(z)
b) Tm(z) = zTm-1(z) – 2Tm-2(z)
c) Tm(z) = 2Tm-1(z) – zTm-2(z)
d) Tm(z) = Tm-1(z) – 2zTm-2(z)

Explanation: The Chebyshev polynomial of any order m can be derived from the recursive formula. This is one of the main features of the Chebyshev polynomial. It is given by
Tm(z) = 2zTm-1(z) – Tm-2(z).

5. What is the HPBW of the Dolph Chebyshev array if the broadening factor is 2 and HPBW of uniform array is 30°?
a) 30°
b) 60°
c) 90°
d) 120°

Explanation: HPBW of the Dolph Chebyshev array= broadening factor×HPBW of uniform array
=2×30°=60°.
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6. In Chebyshev array which of the following is approximated to the Chebyshev polynomial?
a) Array factor
b) HPBW
c) Side lobe level
d) Range equation

Explanation: The array factor is approximated to the Chebyshev polynomial and the desired side lobe level is maintained similar to the polynomial where constant amplitude is maintained between -1 to 1. Dolph- chebyshev method is used to design array with desired side lobes.

Sanfoundry Global Education & Learning Series – Antennas.