Muhammad Usama QureshiFurqan Shoukat

Muhammad Hashim Hussain

Horn Antenna

Introduction to Antennas

• An antenna is a device that is used to transmit and/or receive an electromagnetic wave.

• The antenna itself can always transmit or receive, but it maybe used for only one of these functions.

• Examples: Cell-phone antenna (transmit and receive) Wireless LAN antenna (transmit and receive) FM radio antenna (receive only) Satellite dish antenna (receive only)

Main properties of antennas

• Radiation pattern

• Directivity (how directional the beam is)

• Efficiency (power radiated relative to total input power)

• Polarization (linear, CP)

• Input Impedance

• Bandwidth (the useable frequency range)

Types of Antennas• Antenna tower a tall tower designed to support antennas (also known as

aerials in the UK) for telecommunications and broadcasting.• Dipole antenna a simple antenna usually constructed from two wires in

opposite phases placed end to end.• Directional antenna or beam antenna, radiates greater power primarily in

one direction.• Horn antenna a type of directional antenna shaped like a horn.• Omni directional antenna an antenna system which radiates power

uniformly in all directions in one plane.• Parabolic antenna an antenna shaped like a parabola in one or both planes.• Power antenna (automotive) A power antenna is an electrically motorized

automotive radio antenna that raises and lowers either manually with a dash-mounted switch or automatically by turning the radio on or off.

Horn Antenna

It acts like a “loudspeaker” for electromagnetic waves.• High bandwidth• Moderate directivity• Commonly used at microwave frequencies and above• Often used as a feed for a reflector antenna

• The horn is nothing more than a hollow pipe of different cross sections, which has been tapered (flared) to a larger opening. An electromagnetic horn can take many different forms, four of which

• The radiation from the aperture antennas, such as open-ended waveguides and horn antennas, can be rigorously calculated from the current distributions on the inside wall and the exterior surface of the aperture-antenna.

E-Plane view

Directivity• The directivity of the H-plane sectoral horn is calculated by

the general directivity expression for apertures.

• The integral in the denominator is proportional to the total radiated power,

Directivity • The directivity of the E-plane sectoral horn is found in a

manner analogous to the H-plane sectoral horn:

where

Directivity• The directivity of the pyramidal horn can be found by

introducing the phase efficiency factors of both planes and the taper efficiency factor of the H-plane

where

Efficiency • The antenna efficiency (or radiation efficiency) can be written

as the ratio of the radiated power to the input power of the antenna:

• The total efficiency of an antenna is the radiation efficiency multiplied by the impedance mismatch loss of the antenna, when connected to a transmission line or receiver (radio or transmitter).

where ML is the antenna's loss due to impedance mismatch.

Gain • Antenna Gain describes how much power is transmitted in

the direction of peak radiation to that of an isotropic source.

Other types of Horn Antenna

• Multimode Horns• Corrugated Horns• Hog Horns• Biconical Horns• Dielectric Horns etc