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Antenna Patterns

Gain for an antenna is expressed in decibels relative to an isotropic radiator (point source that radiates equally in every direction). Physical attributes of an antenna, in conjunction with the operating frequency, results in constructive and destructive interference patterns being set up a points distant from the antenna. Where the fields add constructively a positive gain is experienced, and where fields add destructively a negative gain is experienced (relative to isotropic).


Narrowband BW (%)
   = (fU - fL) / fC
Broadband BW
   = fU / fL
%Ratio
51.05:1
101.11:1
201.22:1
301.35:1
401.50:1
501.67:1
601.85:1
%Ratio
672:1
1003:1
1204:1
1335:1
1507:1
1609:1
16310:1

Note:  Keep dimensional units similar; i.e., meters, inches.
Parabolic Antenna
Parabolic antenna coordinates and radiation pattern - RF CafeParabolic antenna coordinates and radiation pattern - RF CafeGain (typ): 10 to 60 dB

Bandwidth: 33% (1.4:1)

Frequency Limit: Lower - 400 MHz
   (due to size)    Upper - 13+ GHz

Polarization: Polarization of feed

Half-Power Beamwidth: 1 to 10º
G=20 log (D/λ) + 10 log (a) + 9.938 dB  D= diameter
  a = illumination factor
                 (typ = 0.6)
  λ = wavelength
Dipole Antenna, 1/2 Wave
 1/2-wave dipole antenna coordinates and radiation pattern - RF Cafe1/2-wave dipole antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern
Gain (typ): 2 dB

Bandwidth: 10% (1.1:1)

Frequency Limit: Lower - none
                           Upper - 8 GHz
                              (due to size)

Polarization: Linear (vertical as shown)

Half-Power Beamwidth (typ): 80º x 360º

Notes: Pattern and lobing change significantly with L/f. Used as gain reference for f < 2 GHz.
1/2-wave dipole antenna coordinates and radiation pattern - RF Cafe
Azimuth Pattern
Vertical Whip Antenna, 1/4 Wave
 1/4-wave dipole antenna coordinates and radiation pattern - RF Cafe
Configuration
1/4-wave dipole antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern
Gain (typ): 2 to 6 dB

Bandwidth: 10% (1.1:1)

Frequency Limit: Lower - none
                           Upper - none

Polarization: Linear (vertical as shown)

Half-Power Beamwidth (typ):
                                    45º x 360º

Notes: Polarization changes to horizontal if antenna is rotated to horizontal.
1/4-wave dipole antenna coordinates and radiation pattern - RF Cafe
Azimuth Pattern
Log-Periodic Array
   
 
Yagi Array
Yagi antenna coordinates and radiation pattern - RF CafeYagi antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern
Gain (typ): 5 to 15 dB

Bandwidth: 5% (1.05:1)

Frequency Limit: Lower - 50 MHz
                           Upper - 2 GHz

Polarization: Linear (horizontal as shown)

Half-Power Beamwidth (typ):
                                      50º x 50º
Yagi antenna coordinates and radiation pattern - RF Cafe
Azimuth Pattern
Circular Loop
Circular loop antenna coordinates and radiation pattern - RF CafeCircular loop antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern
Gain (typ): -2 to 2 dB

Bandwidth: 10% (1.1:1)

Frequency Limit: Lower - 50 MHz
                         Upper - 1 GHz

Polarization: Linear (horizontal as shown)

Half-Power Beamwidth (typ):
                                     80º x 360º
Circular loop antenna coordinates and radiation pattern - RF Cafe
Azimuth Pattern
Square Loop
Square loop antenna coordinates and radiation pattern - RF CafeSquare loop antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern
Gain (typ): 1 to 3 dB

Bandwidth: 10% (1.1:1)

Frequency Limit: Lower - 50 MHz
                         Upper - 1 GHz

Polarization: Linear (horizontal as shown)

Half-Power Beamwidth (typ):
                                  100º x 360º
Square loop antenna coordinates and radiation pattern - RF Cafe
Azimuth Pattern
Horn
Horn antenna coordinates and radiation pattern - RF CafeHorn antenna coordinates and radiation pattern - RF Cafe
3 dB beamwidth 56 * λ / h
Elevation Pattern
Gain (typ): 5 to 20 dB

Bandwidth: 120% (4:1) - ridged
                 67% (2:1) - non-ridged

Frequency Limit: Lower - 50 MHz
                         Upper - 40 GHz

Polarization: Linear (vertical as shown)

Half-Power Beamwidth (typ):
                                       40º x 40º
Horn antenna coordinates and radiation pattern - RF Cafe
3 dB beamwidth 70 * λ / w
Azimuth Pattern


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