PARABOLIC ANTENNA
BY: BSECE 5-1
CAUAN , JHOANIE MARIE P.
ROLLO, JUSTINE MAE E.
PARABOLIC ANTENNA
• A parabolic antenna is an antenna that uses a parabolic reflector,
a curved surface with the cross-sectional shape of a parabola, to
direct the radio waves.
• The most common form is shaped like a dish and is popularly
called a dish antenna or parabolic dish.
PARABOLIC ANTENNA
• The parabolic antenna was invented by German
physicist Heinrich Hertz during his discovery of radio
waves in 1887. He used cylindrical parabolic reflectors
with spark-excited dipole antennas at their focus for both
transmitting and receiving during his historic experiments.
ADVANTAGE OF PARABOLIC ANTENNA:
• high directivity
• functions similarly to a searchlight or flashlight reflector
• have some of the highest gains; can produce the narrowest beam
widths,
COMMON APPLICATION OF PARABOLIC
ANTENNA
• as high-gain antennas for point-to-point communications
• microwave relay links that carry telephone and television signals between
nearby cities,
• wireless WAN/LAN links for data communications,
• satellite communications and spacecraft communication antennas.
COMMON APPLICATION OF PARABOLIC
ANTENNA
• radio telescopes.
• radar antennas to locate objects like ships, airplanes, and guided missiles
• weather detection.
• home satellite television receivers
PARTS OF A PARABOLIC ANTENNA
• A typical parabolic antenna consists of a metal parabolic
reflector with a small feed antenna suspended in front of
the reflector at its focus, pointed back toward the
reflector.
PARTS OF A PARABOLIC ANTENNA
•Parabolic reflector - The reflector is a metallic surface
formed into a paraboloid of revolution and usually
truncated in a circular rim that forms the diameter of the
antenna
PARTS OF A PARABOLIC ANTENNA
Parts of the Parabolic Reflector
1. Focus – is where all incoming radio waves are
concentrated.
2. Vertex – is the innermost point at the center of the
parabolic reflector.
3. Focus Length – is the distance from its focus to its
vertex.
4. Aperture – the opening and is described by its
diameter.
PARTS OF A PARABOLIC ANTENNA
• Feed antenna - emits
radio waves back toward
the dish and reflect off
the dish into a parallel
beam.
PARABOLIC ANTENNAS ARE DISTINGUISHED BY
THEIR SHAPES:
PARABOLOIDAL OR DISH
• The reflector is shaped like
a paraboloid truncated in a
circular rim. This is the most
common type. It radiates a
narrow pencil-shaped beam
along the axis of the dish.
SHROUDED DISH
• The shroud shields the
antenna from radiation
from angles outside the
main beam axis, reducing
the sidelobes
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. The curved ends of the
reflector are sometimes capped by flat
plates, to prevent radiation out the ends,
and this is called a pillbox antenna.
PARABOLIC ANTENNAS ARE ALSO CLASSIFIED BY
THE TYPE OF FEED, THAT IS, HOW THE RADIO
WAVES ARE SUPPLIED TO THE ANTENNA:
AXIAL OR FRONT FEED
• This is the most common type of feed, with
the feed antenna located in front of the
dish at the focus, on the beam axis,
pointed back toward the dish. A
disadvantage of this type is that the feed
and its supports block some of the beam,
which limits the aperture efficiency to only
55–60%
OFF-AXIS OR OFFSET FEED
• The reflector is an asymmetrical
segment of a paraboloid, so the focus,
and the feed antenna, are located to
one side of the dish. The purpose of
this design is to move the feed
structure out of the beam path, so it
does not block the beam.
CASSEGRAIN
• In a Cassegrain antenna, the feed is
located on or behind the dish, and radiates
forward, illuminating a
convex hyperboloidal secondary reflector
at the focus of the dish. The radio waves
from the feed reflect off the secondary
reflector to the dish, which forms the
outgoing beam.
CASSEGRAIN
• In a Cassegrain antenna, the feed is
located on or behind the dish, and radiates
forward, illuminating a
convex hyperboloidal secondary reflector
at the focus of the dish. The radio waves
from the feed reflect off the secondary
reflector to the dish, which forms the
outgoing beam.
CASSEGRAIN
• In a Cassegrain antenna, the feed is
located on or behind the dish, and radiates
forward, illuminating a
convex hyperboloidal secondary reflector
at the focus of the dish. The radio waves
from the feed reflect off the secondary
reflector to the dish, which forms the
outgoing beam.
GREGORIAN
• Similar to the Cassegrain
design except that the
secondary reflector is concave,
(ellipsoidal) in shape. Aperture
efficiency over 70% can be
achieved.
GREGORIAN
• Similar to the Cassegrain
design except that the
secondary reflector is concave,
(ellipsoidal) in shape. Aperture
efficiency over 70% can be
achieved.
THANK YOU!
