Antennas & their Types

Presented By:ZAHOOR AHMAD WANI

Introduction to Antennas

ANTENNA - Definition

An Antenna (aerial) is an electrical device which converts electric energy into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver.

An antenna is a device used for sending or receiving Electromagnetic waves.

An antenna Consists of a Transmitter and a Receiver.

TRANSMITTER of ANTENNA

A device that converts sound, light, or electrical signals into radio, microwave, or other electrical signals .

RECEIVER of ANTENNA

An antenna used to

convert electromagnetic

waves into electrical

energy.

PARAMETERS OF ANTENNA

BANDWIDTH It specifies the range of frequencies over which its performance does

not suffer due to a poor impedance match. 

GAIN Gain is a parameter which measures the degree of directivity of the

antenna's radiation pattern.

EFFECTIVE AREA OR APERTURE The effective area or effective aperture of a receiving antenna

expresses the portion of the power of a passing electromagnetic wave .

RADIATION PATTERN It is typically represented by a three dimensional graph, or polar plots of the

horizontal and vertical cross sections. 

IMPEDANCE As an electro-magnetic wave travels through the different parts of the antenna

system it may encounter differences in impedance.

POLARIZATION The polarization of an antenna is the orientation of the electric field (E-plane) of the

radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation.

EFFICIENCY Efficiency of a transmitting antenna is the ratio of power actually radiated (in all

directions) to the power absorbed by the antenna terminals.

PARAMETERS OF ANTENNA

TYPES OF ANTENNAS

There are various types of Antennas and few of them are:

1. YAGI – UDA ANTENNA

2. HELIX ANTENNA

3. PARABOLIC ANTENNA

4. LOOP ANTENNA

5. HORN ANTENNA

1.YAGI – UDA ANTENNA

Yagi - Uda Antenna consists of:

A Reflector Director and a

Driven element. It is a Unidirectional antenna. Frequency range – 300MHz - 3GHz.

Seven Element Yagi –Uda Antenna

Yagi – Uda - Advantages

1. High gain and good front to back ratio.

2. It has narrow bandwidth.

3. It is fixed frequency device.

4. Greater directivity due to director and

reflector.

2. HELIX ANTENNA

A conducting wire in the form of screw thread fed by power source.

The feed line is connected between the bottom of the helix and the ground plane. 

Helix antenna is Omni-directional. Frequency range – VHF and UHF band.

where > VHF= Very High FrequencyUHF= Ultra High Frequency

Helix Antenna

Applications of Helix Antenna

1. Satellite Communication.

2. Space communication & space probes.

3. For Telemetry applications.

3. PARABOLIC REFLECTOR ANTENNA

This is used to convert Spherical wave into Plane wave The feed antenna is called primary antenna and

reflector is secondary antenna. Frequency range - 3GHz-30GHz

Applications

1. Radar communication.2. Satellite communication.

Parabolic Reflector Antenna

4. LOOP ANTENNA

A directional-type antenna consisting of one or more complete turns of a conductor.

It determines the direction of arrival of radio signals.

Frequency range – 500-1600 KHz.

Applications of Loop Antenna

1. Direction finding of signal propagation.

2. Radio (AM/FM) reception.

3. Long distance point to point

Communication.

5. Horn Antennas

Horn antennas are obviously very directional.

The shape of the horn determines if the electric or magnetic fields are maximized.

The gain is very high in the direction of the horn’s axis

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