ANTENNA ARRAY

Jun 17 • Notes • 2335 Views • 2 Comments on ANTENNA ARRAY

ANTENNA ARRAY :

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• GATE 2015 Syllabus for Electronics and Communication Engineering

POINT SOURCE :.

A point source is defined as a radiator that has various dimensions of a point in space.It is represented as :

.

ARRAYS AND POINT SOURCE :

TWO ELEMENT ARRAY :

A  two-element antenna array of  an equilateral triangle antenna on a ferrite substrate are used for theoretical study  by considering the presence of bias magnetic  field in the same  direction of propagation of electromagnetic waves. The natural modes of propagation is in the direction of magnetic  field and the circularly polarized waves  have dielectric propagation constants. In this  loss-less isotropic warm plasma , the  antenna array   geometry excites or interests  both electromagnetic (EM) and electroacoustic plasma (P) waves and is a sum of  two  nonradiating surface waves .

ENDFIRE ARRAY AND BROADSIDE ARRAYS :

An end fire array is defined as a combination of same and equally spaced antenna that radiates by the axis of the axis of any antenna array . A current of similar magnitude and opposite in phase  is fed to the elements and hence because of this unidirectional radiation is obtained .

Broadside array is defined as the maximum radiation that travels along the axis of the array . It is mostly the combination of  many identical antennas that are kept at a line drawn perpendicularly in respective axis .

UNIFORM  LINEAR ARRAYS OF n- ELEMENTS

Uniform linear array has  array elements that are placed on the y axis with a uniform spacing given that is d. The currents  on the elements is different only by a phase angle increase of b given below

where I = reference current

n = 1, 2, – – – -N/2 and

N = number of elements.

ARRAYS OF 2 DRIVEN HALF WAVE LENGTH ELEMENTS :

The number of  half-wave driven antenna elements are placed  with respect to each other so that the  energy from an  individual element will sum to specific directions and then cancel it  in other directions, then the antenna system is called as a directional array .

The Driven arrays are mostly made up of a number of half-wave dipoles placed  and phased such  that the desired directional pattern is achieved. A simple antenna array  consists of two horizontal overloaded  elements,where  each is  of  half wavelength long and is  fed in phase resulting in a radiation pattern,  in a direction of right angle to the plane  that contains  the antenna conductor.

PRINCIPLE OF PATTERN MULTIPLICATION :

The antenna elements  always operate independently. In real situations , the  antennas are  placed in a  close proximity to each other so that it can interact strongly with each other . This is known as  mutual coupling effect and it will distort all  the array properties , like the  array pattern, from those that are based on the pattern multiplication principle. In order to apply the pattern  multiplication  principle we need to follow the mutual coupling condition .

QUESTIONS AND ANSWERS :

QUE > DEFINE POINT SOURCE ?

ANS > A point source is defined as a radiator that has various dimensions of a point in space.

QUE > WHAT IS PATTERN MULTIPLICATION PRINCIPLE ?

ANS > The antenna elements mostly operate independently. In real situations , the  antennas are  positioned  in a  close proximity to each other so that it can interact strongly with each other . This is known as  mutual coupling effect and it will loose  all  the array properties , like the  array pattern, from those that are based on the pattern multiplication principle. In order to apply the pattern  multiplication  principle we need to follow the mutual coupling condition .

QUE> DIFFERENCE BETWEEN AN END FIRE ARRAY AND BROADSIDE ARRAY ?

ANS > The difference between them is that :

An end fire array is  a combination of same and equal spaced antenna that radiates by the axis of the axis of any antenna array . A current of same magnitude and opposite in phase  is fed to the elements and hence because of this unidirectional radiation is obtained .

Broadside array is  the maximum radiation that travels along the axis of the array . It is mostly the combination or sum  of  many identical antennas that are kept at a line drawn perpendicularly in respective axis .

GATE Syllabus-

1.Gate Syllabus for Electronics and Communication 2014

2. Gate syllabus for Engineering Science 2014

IES Syllabus-

1. IES Syllabus for Electronics and Telecomm

2. IES Syllabus for General Ability

ANTENNA ARRAYSendfire array and broadside arrayprinciple of pattern multiplicationquestion and answersunfiform linear arrays of n-elements

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