Antenna Array

List of things we are going to look forward under Antenna Array

List of contents

• Two-element, N-element linear array
• Uniform (amplitude & Spacing) arrays
• Broadside  and  End-fire  array
• Uniform spacing, Non-uniform amplitude arrays
• Binomial array, Dolph-Tschebyscheff array
• Planar  Array,  Circular Array, Log Periodic Antenna, Yagi-Uda Antenna Array

Prerequisite

• Basic Wire Antenna- Infinitesimal Antenna (l<<l)
• Few points about  Single Element an Antenna
• Radiation Pattern is relatively wide.
• Provides low values of directivity (gain)
• Need of Long Dist. Comm. (or many Applications):
• Very directive antennas (Very High Gains)

How to fulfill the need?

• Increasing the size of the Antenna
  • electrical and geometrical
• How to increase the size of an Antenna
  • Two ways:
    • 1.Enlarge the  dimension of single element   
    • 2.Enlarge the dimension of the antenna without increasing the element size, by forming an assembly of radiating elements, i.e. An array.
• The antenna formed by multi elements is referred as an ARRAY
• Elements: Mostly Identical (for simple, convenient & practical)
  •  Forms (Wires, Apertures, etc)

Field of an Array

• The total field of the array is a vector addition of fields of individual elemens.
  • Constructive Interference of the field (Add) of individual elements.
  • Destructive Interference of the field (Cancel) of individual elements.

Five Controls of an Array (Identical Elements)

1. Geometrical Configuration of the overall array.
   1. Linear, Circular, Rectangular, Spherical
2. Relative Displacement between the elements
3. The excitation amplitude of the individual element
4. The excitation Phase of the individual elements
5. The relative pattern of the individual elements

Array Analysis

FIELD EQUATIONS OF SINGLE  ELEMENT

Infinitesimal Dipole

TWO ELEMENT ARRAY

Total Field

Pattern Multiplication

“ The product of the field of a single element at a selected reference point (usually origin) and the Array Factor of that array is called as the concept of Pattern Multiplication”

Array Factor

N-Element Linear Array: Uniform Amplitude and Spacing

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