Radiation Patterns of Antenna (Isotropic Antenna, Directional Antenna & Omnidirectional Antenna)
i) Radiation Pattern of Isotropic Antenna
• Isotropic Antenna radiates equally in all directions.
• Hence, Its radiation pattern will be a sphere.
• So, the Isotropic antenna has equal gain in all directions.
• It has Only a Single Lobe in its radiation.
(Lobe: The region of the radiation pattern containing the power or exhibiting field strength)
ii) Radiation Pattern of Directional Antenna
• Directional Antenna radiates maximum in the direction of Major Lobe.
• Directional Antenna also has side Lobes.
• Directional Antenna may have a back Lobe opposite to the Major lobe.
• Other than Major Lobe is also known as Minor Lobes.
(Lobe: The region of the radiation pattern containing the power or exhibiting field strength.
Major Lobe: The region of the radiation pattern containing the highest power or exhibiting the greatest field strength.)
iii) Radiation Pattern of Omni-Directional Antenna
• Omnidirectional Antenna radiates in plane.
• Radiation plane may be XY, YZ, or XZ plane.
• So, a Major Lobe will be there in a Radiation Plane and It may have minor lobes.
• In Omni-Directional Antenna we don't have back Lobe.
Parameters of Radiation Patterns (Half Power Beam Width, First Null Beam Width & Front to Back Ratio)
Basics of Radiation Patterns
• Radiation Pattern explains the radiation characteristics of the Antenna.
• Radiation Pattern shows the strength of radiation of a given Antenna.
Polar Representation & Rectangular Representation of Radiation Pattern
Lobe
• The region of the radiation pattern containing the power or exhibiting field strength.
Major Lobe
• The Lobe of the radiation pattern containing the highest power or exhibiting the greatest field strength.
Back Lobe
• The Lobe Opposite to the Major Lobe is Back Lobe.
Minor Lobes
• Other Than the Major Lobe are Minor Lobes.
Side Lobes
• Other Than the Major Lobe and Back Lobe are Side Lobes.
HPBW (Half Power Beamwidth)
• It is the angular width of Major Lobe from Maximum Gain to 3dB Down gain.
FNBW (First Null Beamwidth)
• It is the angular width of the Major Lobe.
Front to Back Ratio
• It is the ratio of gain from the Major Lobe to Back Lobe.
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