GOVERNMENT ENGINERING COLLEGE-BHARUCH(014)

ANTENNA & WAVE PROPAGATION [2161003]

LOOP ANTENNAS

6TH SEM. E.C. DIV. : A BATCH : A3

Made By

PRATIK NAKRANI 130140111046

Guided By

Prof. Mukesh Chaurasiya

Wire antenna

1. Linear wire antenna

2. Loop antenna

3. Helical antenna

Aperture antenna

Micro strip antenna

Reflector antenna

Lens antenna

Types of Antenna

An antenna is a sensor of electromagnetic waves. It acts like transducer which converts electrical energy into EM energy at transmitting side and EM energy into electrical energy at the receiving side.

Also it is impedance matching device as it matches the impedance of the transmitter and free space.

Antenna

Linear wire Antenna

When Current passed through straight wires, it results in radiation

Loop Antennas Instead of keeping straight if we turned into loop , it results in radiation

Generally , Loop have any shape! But Square and circular loop is popular.

Types Of Loop [Dimensions] • When Overall length of loop is less then one-tenth

of wave length.• N* Circumference < N = Number of Turns

Electrically Small Loop

• When Overall length of loop is • These Loops will have maximum radiation along perpendicular to the loop

Electrically Large Loop

Properties

Electrically Small Loop • The Radiation pattern of these loops will have null

direction perpendicular to the plane of loop.• These have small radiation resistance () Thus Radiation

is Poor Hence Rarely used in Transmission• But they can use for receiving antennas in Radios• can be increased by increasing it’s size or number of

Turns [N].• Another way to increase is to insert within its

circumference or perimeter, a ferrite core of very high permeability () FERRITE LOOP it’s increases the H hence

Small LoopAntennas

• When Overall length of loop is less then one-tenth of wave length is called small loop antenna.

a

I

Id

d

Circular loop Area

Square loop Area [

Radiation Pattern for Both the loop is same when =

The Radiation Fields of small loops are independent of shape of the loop but only depends upon the area of the loop therefore we select the square loop for simple analysis

Radiation Pattern

Radiation Resistance

This relates the power supplied to the antenna and the current flowing into the antenna.

For loop antenna,

= ᾒ

The greater the radiation resistance, the more energy is radiated or received by the antenna.

The directivity measures the antenna’s ability to concentrate its power in a given direction

The directivity is the same as that of an infinitesimal dipole.

The radiation characteristics of a small loop antenna can be additionally improved by inserting a ferromagnetic core.

Directivity

Loop antennas feature simplicity, low cost and versatility.

Much less affected by human body movement than other antennas and is therefore suitable for indoor installations.

Potential gain up to 2dB compared to a half wave length dipole

Exhibits the same radiation pattern as dipole.

Advantages

For maximum efficiency the antenna must be vey large for FM

The antenna is rarely used for transmission because of its small radiation efficiency.

Disadvantages

Small loop antenna is used as receiving antenna in radios and pagers.

Used in applications involving HF(3-30MHz),VHF(30-300MHz) and UHF(300-3000MHz).

They can also be used in microwave range (1GHz-100GHz) as field probes.

Applications

Thank You

Image credits : Amazon India LtdCompatible in : Microsoft office 2013