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 = (f_U - f_L) / f_C
%	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 = f_U / f_L
%	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 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

1/2-wave dipole antenna coordinates and radiation pattern - RF Cafe

1/2-wave dipole antenna elevation radiation pattern - RF Cafe

Elevation Pattern 1/2-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.

1/4-wave dipole antenna coordinates and radiation pattern - RF Cafe

Configuration

1/4-wave dipole antenna elevation radiation pattern - RF Cafe

Elevation Pattern 1/4-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 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 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 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 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 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 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, Electromagnetics & X-mission Line Simulators

- Satellite Communications - Antennas

- Short Wire Antennas

Windfreak Technologies Frequency Synthesizers - RF Cafe


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