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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). These drawings and parameters were derived from the EW and Radar Systems Engineering Handbook.

Narrowband BW (%) = (fU - fL) / fC
% Ratio % Ratio
5 1.05:1 40 1.50:1
10 1.11:1 50 1.67:1
20 1.22:1 60 1.85:1
30 1.35:1    
Broadband BW = fU / fL
% Ratio % Ratio
67 2:1 150 7:1
100 3:1 160 9:1
120 4:1 163 10:1
133 5:1    
       
       
       
Parabolic Antenna
Parabolic antenna coordinates and radiation pattern - RF Cafe Parabolic antenna elevation & azimuth radiation pattern - RF Cafe
G=20 log (D/λ) + 10 log (a) + 9.938 dB

  D= diameter
  a = illumination factor (typ = 0.6)
  λ = wavelength

Keep dimensional units similar;
  i.e., meters, inches.
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
Dipole Antenna, 1/2 Wave
1/2-wave dipole antenna coordinates and radiation pattern - RF Cafe 1/2-wave dipole antenna elevation radiation pattern - RF Cafe

Elevation Pattern1/2-wave dipole antenna azimuth radiation pattern - RF Cafe
Azimuth 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 BW (typ):
    80º x 360º

Notes: Pattern and lobing change significantly with L/f. Used as gain reference for f < 2 GHz.
Vertical Whip Antenna, 1/4 Wave
 1/4-wave dipole antenna coordinates and radiation pattern - RF Cafe
Configuration
1/4-wave dipole antenna elevation radiation pattern - RF Cafe

Elevation Pattern1/4-wave dipole antenna azimuth radiation pattern - RF Cafe
Azimuth 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 BW (typ):
    45º x 360º

Notes: Polarization changes to horizontal if antenna is rotated to horizontal.
Log-Periodic Array
Log periodic antenna coordinates - RF Cafre Log periodic antenna elevation radiation pattern - RF Cafre
Elevation Pattern

Log periodic antenna azimuth radiation pattern - RF Cafre
Azimuth Pattern

Polarization: Linear

Half-Power BW (typ):
60º x 80º

Gain (typ): 6 to 8 dB

Bandwidth: 163% or 10:1

Frequency Limit:
    Lower: 3 MHz
    Upper: 18 GHz

Remarks: This array may be formed with many shapes including dipoles or toothed arrays.

Yagi Array
Yagi antenna coordinates - RF Cafe Yagi antenna elevation radiation pattern - RF Cafe
Elevation Pattern

Yagi antenna azimuth radiation pattern - RF Cafe
Azimuth 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 BW) (typ):
    50º x 50º
Circular Loop
Circular loop antenna coordinates and radiation pattern - RF Cafe Circular loop dipole antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern

Circular loop antenna coordinates and radiation pattern - RF Cafe
Azimuth 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 BW (typ):
    80º x 360º
Square Loop
Square loop antenna coordinates and radiation pattern - RF Cafe Square loop antenna coordinates and radiation pattern - RF Cafe
Elevation Pattern
Square loop antenna coordinates and radiation pattern - RF Cafe
Azimuth 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 BW (typ):
    100º x 360º
Vee
Vee antenna coordinates and radiation pattern - RF Cafe


Vee antenna elevation & azimuth radiation pattern - RF Cafe
Elevation & Azimuth Pattern

 

Polarization: Linear
         (vertical as shown)
Half-Power BW (typ):
    60 deg x 60 deg
Gain (typ): 2 to 7 dB
Bandwidth: "Broadband"
Frequency Limit:
    Lower: 3 MHz
    Upper: 500 MHz
          (practical limit)
Remarks: 24 kHz versions are known to exist. Terminations may be used to reduce back lobes.
Horn
Horn antenna coordinates and radiation pattern - RF Cafe Horn antenna elevation radiation pattern - RF Cafe
3 dB beamwidth 56 * λ / h
Elevation Pattern
Horn antenna azimuth radiation pattern - RF Cafe
3 dB beamwidth 70 * λ / w
Azimuth 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 BW (typ):
    40º x 40º

Related Pages on RF Cafe
- Antenna Patterns
- Antennas - Hardware & Controls
- Antennas - Manufacturers & Services
- Test Equipment & Calibration - Antenna Measurement
- Antenna Introduction / Basics
- Antenna Radiation Patterns
- Antenna Near Field
- Near-Field / Far-Field Transition Distance
- Intro to Wave Propagation, Transmission Lines, Antennas
- Antenna Design Resources
- Antenna, Electromagnetics & X-mission Line Simulators
- Satellite Communications - Antennas
- Short Wire Antennas