antennas & their associated patterns
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Antennas & theirassociated patterns
Mr.Song KepingEngineer of Management of station and network Division
State Radio Monitoring Center
[email protected]+8610-68318264
Radio Monitoring and Spectrum Management Training
(China,23-31,May,2005)
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Definitions associate with antenna
HF antenna types
VHF and UHF omnidirection types
VHF and UHF directional types
Antennas for frequencies above3 000 MHz
Antennas & theirassociated patterns
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Definitions associate with antenna
HF antenna types
VHF and UHF omnidirection types
VHF and UHF directional types
Antennas for frequencies above3 000 MHz
Definitions associate withantenna
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Antenna
-Definition:
System of wires or other conductors that used to transmit
or receive radio waves or electromagnetic fields
-Transform between current and radio wave
Definitions associate withantenna
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Antenna gain
-Definition:
When produce same field strength of the same powerflux-density at the same distance in a given direction, the
ratio of the power required at the input of a loss free
reference antenna to the power supplied to the input of a
given antenna.
-Refers to the direction of maximum radiation
-Considered for a specified polarization
Definitions associate withantenna
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Antenna gain (2)
-Gi: isotropic antenna as reference (expressed in dBi)
-Gd: half-wave dipole as reference (expressed indBd)
-Gv: linear conductor as reference (expressed in dBv,not in common use)
dBi = dBd + 2.15 dB
Definitions associate withantenna
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Antenna directivity diagram(pattern)
-A curve representing a quantity proportional tothe gain of antenna in the various direction in aparticular plane
-Main lobe and side lobe
-Horizontal directivity diagram
-Vertical directivity diagram
Definitions associate withantenna
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Definitions associate withantenna
Example of main lobe and side lobe
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Definitions associate withantenna
Horizontal (left) and vertical (right) radiation pattern of an antenna
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Polarization of a radio wave
-The orientation of the electric flux in the EM field
-Linear polarization (vertical, horizontal)
-Circular polarization (right hand, left hand)
Polarization of an antenna
-Polarization of the signals it transmit
Definitions associate withantenna
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Bandwidth of antenna
-Range of frequencies over which its effective
-Techniques that can increase the bandwidth
Active antenna
-Active processing before intercepting or producing
-Has active elements in front of the output
Definitions associate withantenna
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Active antenna (2)
-Wide bandwidth
-Good shape of radiation pattern
-Small size
-Frequency-impendence parameters
-Influenced by intermodulation and cross-modulation
-Weak to nearby lightning
Definitions associate withantenna
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Definitions associate with antenna
HF antenna types
VHF and UHF omnidirection types
VHF and UHF directional types
Antennas for frequencies above3 000 MHz
HF antenna types
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Rotatable horizontally polarized log-periodic
antenna
-Broadband
-Rotatable for different direction-Consistent pattern over the entire frequency range
-Typical gain: 12dBi
-Suitable for medium and long range skywave
-Suitable for short range ground wave
HF antenna types
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Horizontally log-periodic HF antenna in Beijing monitoring station
and typical horizontal(top) and vertical(bottom) radiation pattern
HF antenna types
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HF Quadrant antenna
-Consist of horizontal bent dipoles
-Bent angle different for required horizontal pattern
-Cannot cover entire HF band
-Dipole is performed as an open multi-wire cage
HF antenna types
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Quadrant antenna and typical horizontal (top) and vertical (bottom)
radiation pattern
HF antenna types
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Quadrant antenna in Beijing monitoring station
HF antenna types
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Vertically polarized monopole omnidirectionalantenna
-Broadband
-Composed of a biconical cage of wire
-Typical gain: 4~5dBi
-Suitable for short range ground wave-Suitable for moderate to long range skywave
HF antenna types
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Broadband vertical omnidirectional antenna and typical horizontal
(top) and vertical (bottom) radiation pattern
HF antenna types
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Magnetic loop antenna
-Very small size
-Detects the magnetic field
-Can be installed in low height.
-Sometimes active
-Suitable for monitoring and measurement
HF antenna types
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Example of magnetic loop antenna
HF antenna types
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Definitions associate with antenna
HF antenna types
VHF and UHF omnidirection types
VHF and UHF directional types
Antennas for frequencies above3 000 MHz
VHF and UHF omnidirectiontypes
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Active Receiving Dipole antenna
-Small size
-High sensitivity-Wide dynamic range
-Wide bandwidth
-Typical gain: 5dBi
VHF and UHF omnidirectiontypes
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Active receiving dipole antenna
VHF and UHF omnidirectiontypes
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Rod antenna
-Cover different frequency range
-Sometimes active
VHF and UHF omnidirectiontypes
Active rod antenna
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Coaxial Dipole antenna
-Vertically polarize
-Suitable for mobile use-Typical gain : 2dBi @800MHz
VHF and UHF omnidirectiontypes
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Coaxial dipole antenna and typical horizontal (top) and vertical
(bottom) radiation pattern
VHF and UHF omnidirectiontypes
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Definitions associate with antenna
HF antenna types
VHF and UHF omnidirection types
VHF and UHF directional types
Antennas for frequencies above3 000 MHz
VHF and UHF directional types
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VHF and UHF directional types
VHF/UHF Log-periodic antenna
-Suitable for both wide and narrow band application
-Very wide frequency range
-Frequency-independent radiation patterns
-Sometimes be individual calibrated-Typical gain: 6.5dBi
VHF and UHF directional types
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Log-periodic antenna and typical horizontal (top) and vertical(bottom) radiation pattern
VHF and UHF directional types
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Yagi antenna
-Widely used in VHF/UHF band
-Include the driven element, reflectors and directors
-Concentrates the radiation and response
-More directors, greater gain
-More directors, more directional
VHF and UHF directional types
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VHF and UHF directional types
Number of directors -6dB beam width Gain (dB)
4 46 12
9 37 14
13 31 15
20 26 16
Relationship between the number of directors, beamwidth and gain ofYagi antenna
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Yagi antenna and typical radiation pattern
VHF and UHF directional types
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Portable directional antenna
-For portable use-Normally active
-Broadband, small size and low weight
VHF and UHF directional types
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Active portable antenna and typical horizontal (left) and vertical(right) radiation pattern
VHF and UHF directional types
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Definitions associate with antenna
HF antenna types
VHF and UHF omnidirection types
VHF and UHF directional types
Antennas for frequencies above3 000 MHz
Antennas for frequencies above3 000 MHz
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Dish and feed form
-To achieve the necessary of high gain-A feeder in the focus of a parabolic reflector
Gain depend on:-Relation between dish diameter and wavelength-Efficiency
Antennas for frequencies above3 000 MHz
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Examples of typical dishand feed antenna with afeeder and a parabolic
reflector
Antennas for frequencies above3 000 MHz
Examples of a log-periodicantenna as a feeder
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Narrow-band application
-Need very high gain
-To achieve high efficiency
-Minimize the losses caused by insufficientreflection and side radiation
Monitoring or surveillance application
-Need high gain and broad beamwidth-Focusing and defocusing the antenna feed
-By a motor-driven mechanical equipment
Antennas for frequencies above3 000 MHz
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Wideband application
-Need high gain and broad bandwidth
-Often use log-periodic antenna
-Minimizing the losses caused by defocusing
-By a motor-driven mechanical equipment
Antennas for frequencies above3 000 MHz
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Horn antenna
-Broadband
-Compact-Frequency-dependence high gain-Suitable for accuracy measurement
Antennas for frequencies above3 000 MHz
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Horn antenna
Antennas for frequencies above3 000 MHz
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Mount on a tripod or a tower
-For stably face to a certain direction
-Match the direction of the antenna and the signal
-Adjust to desired direction
Antennas for frequencies above3 000 MHz
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Electric antenna rotator
Antennas for frequencies above3 000 MHz