IQRA NATIONAL UNIVERSITY

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Parabolic Antenna

Definition Terminologies Basic Antenna Types Types of shapes Radiation Pattern Concept Features Applications

Contents

A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of arabola, to direct the radio waves.

It is often referred to as a dish antenna.

Parabolic antenna

Focus-The focus is where all the incoming radio waves are concentrated.

Vertex-The vertex is the innermost point at the center of the parabolic reflector.

Focal length-The focal length of a parabola is the distance from its focus to its vertex.

Aperture-The aperture of a parabolic reflector is its opening and is described by its diameter.

Terminologies

Radiation Pattern Concept

Antenna Test Range

Antenna Under Test

Source Antenna

Parabolic reflector

A parabolic reflector

adds all the fields from a surface = aperture at a focal point

Hyperbolic reflector

.A

Light from the point A

.B

appears to come from point Breflecting off the hyperbola

Hyperbolic reflector:

Hyperbolic reflector:

B

Light converging towards B

A

converges at Areflecting off the hyperbola

Parabolic reflector

Parabolic reflector

Hyperbolic reflector

Parabolic primary & Hyperbolic secondary

AT antenna:•Cassegrain configuration•22-m diameter primary main reflector•2.75-m secondary reflector

Signal path

Basic Antenna Types

Standard Parabolic Antenna

Shielded Antenna

Focal Plane Antenna

GRIDPAK® Antenna

Parabolic antennas are distinguished by their shapes. Paraboloidal or dish Shrouded dish Cylindrical

Type of shapes

Paraboloidal or dish

The reflector is shaped like a paraboloid. This is the most common type.It radiates a narrowpencil-shaped beam along the axis of the dish.

Shrouded dish

The shroud shields the antennafrom radiation from angles outside the main beam axis, reducing the side lobes.

Shrouded microwave relay dishes on a communications tower in Australia.

Cylindrical

The reflector is curved in only one direction and flat in the other.The radio waves come to a focus not at a point but along a line.

Features of Parabolic antenna

Greater Directivity and Gain. Parabolic or dish antennas are NOT

frequency dependant. Receives and radiates signals only in

one direction. Produce sharp and narrow beamwidth

of any antenna types. Handy for end users (small reflector

antenna).

Applications Parabolic antennas are used as High gain antennas for point to point communication In applications such as microwave relay links that carry

telephone and television signals between nearby cities Wireless WAN/LAN links for data communications

satellite and spacecraft communication antennas Radio telescopes Radar antennas Satellite television dish antennas

Any Question