Horn Antennas

Basic Concept The horn antenna gains its name from its appearance Type of Aperture antenna A horn antenna is used for the transmission and reception of microwave signals

The horn antenna may be considered as an RF transformer RF transformers match the Impedance to achieve maximum power transfer and to suppress undesired signal reflection. Tapered or flared end enables the impedance to be matched Spot Area Coverage Basic Concept Cntd….

Design Used in conjunction with waveguide feeds

Waveguides A waveguide is a special form of transmission line consisting of a hollow, metal tube Works only for signals of extremely high frequencies

Radiation Pattern

Major Types Of Horn Antenna Pyramidal Horns Conical Horns Corrugated Horns

Multiflare Horn Lens Corrected Horn Hog Horn Dual Mode Horn Some Other Types

Pyramidal Horn

Basic Properties Rectangular Gain DB Easy Fabrication

Radiation Pattern

Pattern For Phase And Amplitude

Conical Horn

Basic Details Also called Open Ended Waveguides Used commonly with multiple beam antennas(MPAs) Wide Bandwidth Has an excellent VSWR for large aperture Easy Fabrication Used as Array elements

Directivity Gain Pattern

Corrugated Horn

Basic Details The name “Corrugated” means shaped into alternating parallel grooves and ridges Used in most of all communication satellites Complete earth coverage FOV +- 9* Medium Antenna Gain Difficult Fabrication

Corrugated Horn

Radiation Pattern

Uses Of Horn Antennas Horn antennas are commonly used as the active element in a dish antenna, the horn is orientated towards the reflector surface, and is able to give a reasonably even illumination of the surface without allowing radiation to miss the reflector, minimizing loss of energy around the edges of the dish reflector Used in Almost all of the Satellites Horn antennas are used in short-range radar systems, to measure the speeds of approaching or retreating vehicles It provides a significant level of directivity and gain

Some Pictures

Helix Antenna

Introduction The helix antenna, invented in the late fourties by John Kraus (W8JK) Specially for frequencies in the range GHz Design is very easy, practical, and, non critical.

Cntd……… Frequencies around 2.4 GHz which can be used for e.g. high speed packet radio (S5-PSK, Mbit/s), 2.4 GHz wavelans, and, amateur satellite (AO40) Developments in wavelan equipment result in easy possibilities for high speed wireless internet access using the b (aka WiFi) standard.

Theory The helix antenna can be considered as a spring with N turns with a reflector The circumference (C) of a turn is approximately one wavelength (l) The distance (d) between the turns is approx. 0.25C The size of the reflector (R) is equal to C or l, and can be a circle or a square

Theory Cntd….. The design yields circular polarization (CP), which can be either 'right hand' or 'left hand' (RHCP or LHCP respectively), depending upon how the helix is wound To have maximum transfer of energy, both ends of the link must use the same polarization, unless you use a (passive) reflector in the radio path

Gain The gain (G) of the antenna, relative to an isotrope (dBi), can be estimated by: G = * log {(C/l)^2 * N * d} dBi

Characteristic Impedence The characteristic impedance (Z) of the resulting 'transmission line' empirically seems to be: Z = 140 * (C/l) Ohm

Radiation pattern

Single & Double Helix Patterns

Different Uses