# Antennas Study Notes for Electronics and Communication Engineering for GATE EC Exam

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Antennas Study Notes for Electronics and Communication Engineering for GATE EC Exam: In this article, you will find the Study Notes on Antennas which will cover the topics such as Introduction, Basic Antenna parameters, Dipole antenna, Antenna’s Power and field, Radiation Pattern, Antenna Characteristics and Important Antenna’s.

Table of content

## Antenna

An antenna is a way for linking the electromagnetic waves from transmitter to receiver.

A resonant antenna is a transmission line whose length is exactly equal to the multiple of half wavelength, i.e.,

where, n = 1, 2, 3,….. positive real integer and λ is wavelength.

Basic Antenna Parameters: Antenna parameters are the factors that select the antenna for particular reason or application.

Directivity: Directivity is defined as the ratio of radiation intensity in particular direction to average radiation intensity i.e.,

• U(θ, φ) = radiation intensity in a direction
• Uav = average radiation intensity

## Dipole Antenna

• A dipole antenna may be defined as a symmetrical antenna in which the two ends are at equal potential relative to mid-point.
• A physical dipole consists of two equal and opposite charges i.e., in the literal sense, two poles.
• The dipole magnetic field lines are shown in the figure.
• A half-wave dipole λ/2 antenna is the fundamental ratio antenna of the metal rod on a thin wire, which has a physical length of half wavelength in free space.

Note: A λ/2 antenna is also known as Hertz antenna or half-wave doublet.

Antenna’s Power and Field: Normalized power and field pattern can be obtained by dividing a power or field component by its maximum value respectively i.e.,

## Normalized power

Normalized field pattern:

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