Antenna Patterns

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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 patternParabolic antenna coordinates and radiation pattern

Gain (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/l) + 10 log (a) + 9.938 dB  D= diameter
  a = illumination factor
                 (typ = 0.6)
  l= wavelength
Dipole Antenna, 1/2 Wave
 1/2-wave dipole antenna coordinates and radiation pattern1/2-wave dipole antenna coordinates and radiation pattern
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
Azimuth Pattern

Vertical Whip Antenna, 1/4 Wave

 1/4-wave dipole antenna coordinates and radiation pattern
Configuration		1/4-wave dipole antenna coordinates and radiation pattern
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
Azimuth Pattern

Log-Periodic Array

   
 

Yagi Array

Yagi antenna coordinates and radiation patternYagi antenna coordinates and radiation pattern
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
Azimuth Pattern

Circular Loop

Circular loop antenna coordinates and radiation patternCircular loop antenna coordinates and radiation pattern
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
Azimuth Pattern

Square Loop

Square loop antenna coordinates and radiation patternSquare loop antenna coordinates and radiation pattern
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
Azimuth Pattern

Horn

Horn antenna coordinates and radiation patternHorn antenna coordinates and radiation pattern
3 dB beamwidth 56 * l / 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
3 dB beamwidth 70 * l / w
Azimuth Pattern