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.

Parabolic Antenna
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
	Elevation Pattern 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
Configuration	Elevation Pattern 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
	Elevation Pattern 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
	Elevation Pattern 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
	Elevation Pattern 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
	Elevation Pattern 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
	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
	3 dB beamwidth 56 * λ / h Elevation Pattern 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

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- Test Equipment & Calibration - Antenna Measurement
- Antenna Introduction / Basics
- Antenna Radiation Patterns
- Antenna Near Field
- Near-Field / Far-Field Transition Distance
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