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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.
Antenna Basics
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Page2Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.
Foreword
z Antenna is most basic and important equipment is radio
network. The specification and selection of antenna is very
important for network QoS.
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Contents
1. Antenna Fundamentals
2. Antenna Working Principle
3. Antenna Specifications
4. Antenna Selection
5. Electric Downtilt Antenna
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Contents
1. Antenna Fundamentals
2. Antenna Working Principle
3. Antenna Specifications
4. Antenna Selection
5. Electric Downtilt Antenna
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Contents
1. Antenna Fundamentals
1.1 Overview
1.2 Antenna type
1.3 Polarization
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Overview
Lightning
Arrester
Main Feeder 7/8
Feeder
Clip
Feeder
Support
Grounding
Point
Antenna Adjustable Support
GSM/CDMA
Panel Antenna
Holding Pole ( 50~114)
BTS
Wall
z In a wireless telecommunication system, the antenna provides the interface between base
transceiver station (BTS) and outside propagation mediums. One set of antenna can both
radiate and receive radio waves. When radiating radio waves, it converts high frequency
current into electromagnetic wave; when receiving radio waves, it converts the
electromagnetic wave into high frequency current.
z During network planning, the right antenna is selected according to the radio environment
of the BTS. The parameters, such as antenna height, antenna azimuth angle, tilt angle, are
decided based on the selected antenna.
z Antenna is directly related to uplink and downlink converges, so are the radio frequency
(RF) components, such as feeder cable, combiner, and duplexer.
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Contents
1. Antenna Fundamentals
1.1 Overview
1.2Antenna type
1.3 Polarization
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Antenna Type
z Vertical polarization antenna
(unipolarization antenna)z Cross polarization antenna
(dual polarization antenna)
Polarization way
z Linear antennaz Panel antennaz Cap antenna
Structural feature
z Omni-directional antennaz Directional antenna
Radiation direction
TypeDivisionstandard
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Antenna Type By Structure
Plate-shape antenna Cap-shape antenna
Whip-shape Paraboloid antenna
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Antenna Type By Polarization
Omni antennaUni-polarization
Directional antenna
Dual polarizationDirectional antenna
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Contents
1. Antenna Fundamentals
1.1 Overview
1.2 Antenna type
1.3 Polarization
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Polarization (Cont.)
z In electromagnetic wave radiated by antenna, the direction ofelectric field vector is the direction of antenna polarization.
Horizontal PolarizationVertical Polarization
+45o Polarization -45o Polarization
z Polarization is a radiation feature describing the direction for the field strength vector of
electromagnetic wave. Generally, the direction of the field strength vector works as the
polarization direction of the electromagnetic wave.
z The electromagnetic wave with the direction of the electric field vector unchanged at any
time is called linear polarized wave. If the land is taken as a reference, the direction of the
electric field vector parallel to the land is called horizontal polarized wave; the direction of
the electric field vector perpendicular to the land is called vertical polarized wave.
z The direction of the electric field vector is changeable. If the trace of the electric field
vector end is a circle, the electromagnetic wave is called circular polarized wave; if the
trace is an ellipse, the electromagnetic wave is called ellipse polarized wave. Both the
circular polarized wave and ellipse have a feature, which is rotating phase.
z The electromagnetic waves of different bands are transmitted by different polarization
modes. Generally, the vertical polarization is used in mobile communication; the horizontal
polarization is used in broadcasting systems; and the ellipse polarization is used in satellite
communication.
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Polarization
z Two antenna combined together, transmit and receive twoindependent wave.
+ 45 / - 45 Polarization0 / 90 Polarization
z The GSM antenna can be divided into two types, namely, single polarization antenna and
dual polarization antenna. With the help of polarization diversity technology, a dual
polarization antenna can promise BTS to receive good signals through reducing the multi-
path effect in mobile communication. Two specifications, 0/90 and 45 are
available to the dual polarization antenna.
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Polarization Loss
z When polarization direction of transmited wave and receivingantenna is different, there will be a Polarization Loss during
receival.
z Linear Polarization wave will take 3dB loss when received by
Circular Polarization antenna.
z Horizontal Polarization antenna can not receive the energy
from Vertical Polarization wave.
In practical Network, you may find such phenomenon: sometimes when cell phone is
vertical( phone on ear side), signal is stronger; when cell phone is horizontal( use
earphone), signal is weaker. Think about why?
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Contents
1. Antenna Fundamentals
2. Antenna Working Principle
3. Antenna Specifications
4. Antenna Selection
5. Electric Downtilt Antenna
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Antenna Radiation (Cont.)z
According to Maxwellequation, electromagnetic
wave radiation can be
generated if alternate
current is present in the
conductor. The radiation
capability is related to the
length and shape of the
conductor.
AA
CC
BB
z As shown in Figure (a), when the distance of the two conductors is short, the induced
electromotive force generated on the ideal conductors will counteract the effect of each
other, so only a small amount of energy is radiated beyond the two conductors.
z As shown in Figure (b), there is a flare angle between the two conductors. Because the
current is generated in the same direction, the induced electromotive force is generated in
the same direction. In this case, a larger amount of energy is radiated beyond the two
conductors.
z As shown in Figure (c), when the flare angle is wide enough to match wavelength, the
amount of current flowing through the conductors will be greatly increased. Thus intensive
radiation is generated.
.
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Antenna Radiation (Cont.)
z The straight conductor that can generate intensive radiation iscalled dipole.
z If the length of the two arms of a dipole is 1/4 wavelength, the
dipole is calledsymmetrical dipole
Dipole
1/2
1/4
1/4
1/2
Wavelength( )
900MHz900MHz -->> : 166mm: 166mm
1800MHz1800MHz -->> : 83mm: 83mm
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Antenna Radiation (Cont.)
z Symmetry Dipole Radiation
Side view
Top view
ConcentrationConcentration
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Antenna Radiation (Cont.)
1mW by one dipole 4mW by array of four dipole
6dB Gain6dB Gain
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Antenna Radiation (Cont.)
z By reflection, radiation energy can be concentrated tosingle direction.
Omni: 4mW Directional: 8mW
Antenna(Top View)
9dB Gain9dB Gain6dB Gain6dB Gain
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Antenna Radiation
z The more the dipole in one
antenna, the more
concentrated the radiated
energy, the higher the
Antenna Gain.
z From one dipole to nine
dipole, Antenna Gain
increase from 0 to 9dBd.
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Contents
1. Antenna Fundamentals
2. Antenna Working Principle
3. Antenna Specifications
4. Antenna Selection
5. Electric Downtilt Antenna
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Electric Specifications
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Frequency Range (Cont.)
z Frequency Range is also calledAntenna Bandwidth.
z Antenna works in specific range frequency. The Central
Frequency (fc) have the best performance, deviation offc
deteriorate the performance.
z Two definition ofAntenna Bandwidth: 3dB deterioration of
Antenna Gain or VSWR too high, typically 1.5. The later one is
commonly used in wireless communication.
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Frequency Range
z Central Frequency850MHz is with best performance. But withinBandwidth 820MHz-890MHz, VSWR
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Directionality
z The Directionalityis the ability of Antenna to radiateelectromagnetic wave in a specific direction.
z As to receiving, it is the ability to receive signal from different
direction. Directionalityis represented byAntenna Pattern
Diagram.
z Antenna Pattern Diagram shows the transmitting and receiving
ability of antenna at different direction of space.
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Antenna Pattern (Cont.)
Horizontal patternHorizontal pattern
Main LobeMain Lobe
First SideFirst Side
LobeLobe
Back LobeBack LobeZero PointZero Point
Horizontal HalfHorizontal HalfPower BandwidthPower Bandwidth
--3dB3dB
Vertical patternVertical pattern
The radiation intensity of Antenna is related to radiation direction. If the relationship between
the two is drawn according to relative scale, it is an Antenna Pattern diagram, or radiation
diagram.
Three relative scales are available for drawing a directional diagram. They are:
z Linearity (power directional diagram)
z Square root (field strength diagram)
z Decibel
The decibel scale is more often used among the three, because it expresses the side lobe level
in a simpler way.
z The Antenna Pattern diagram is 3D figure, but the one in common use is a pattern
diagram within two planes perpendicular to each other, known as plane pattern diagram.
For the linear antenna, since the ground effect is great, it adopts the vertical plane and
horizontal plane as its principle plane. For the plane antenna, it adopts two planes, namely,
E plane and H plane.
z Essentially, the dipole arrangement and the change of the feeding phase of each dipole
work together to determine antenna direction, and the principle is similar to that of the
Light Interference Effect. Therefore, the energy in some directions is amplified, but the
energy in other directions is weakened. In this case, lobes (or beams) and zero points areformed. The lobe with the strongest energy is the major lobe. The lobe with the second
strongest energy is the first side lobe, and so on. For the directional antenna, it has a back
lobe.
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Antenna Pattern (Cont.)
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Antenna Pattern
The ratio of the maximum main lobe power to the
maximum back lobe power.Back lobe cause interference.
Front-to-back ratio
The ratio of the maximum main lobe power to the
maximum side lobe power.Side Lobe SuppressionRatio
Angle included by two direction of 3dB deterioration
than the max transmission direction.Horizontal half power Lobe width and vertical half
Lobe width.
Half Power Lobe Width
When zero depth is -20dB or greater, and theantenna is high, to ensure the coverage, zero point
filling is needed.Zero Point Filling
DescriptionDescriptionParameterParameter
z To make the Coverage better, the first zero point of the lower side lobe needs to be filled
by using the shaped-beam design. Generally, when the zero depth is -20dB greater than
the main beam, it means that the zero point filling is present in antenna.
z It is recommended that the zero point filling technology should be applied to high gain
antennas with great height (for example, the antenna height is 100 meters) to improve
nearby coverage and avoid the unequal coverage caused by signal fluctuation.
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Antenna Gain (Cont.)
z Antenna Gain is an important antenna index, indicating theantenna capability (directional antenna) of concentrating energy
into a certain direction.
Isotropic Antenna
Dipole Antenna
Practical Antenna
dBd
dBi
2.15dB
--70dBm70dBm--85dBm85dBm--87.15dBm87.15dBm
(15)(15)
(17.15)(17.15)
z The antenna is passive equipment, so the concept of antenna gain is different from that of
the power amplifier gain. The power amplifier can amplify power, but the antenna does
not increase the energy for radiated signals. It concentrates the energy into a certain
direction by assembling several antenna dipoles and changing their feeding mode.
z The dBi and dBd are two units of antenna gain, and the relationship between the two is as
follows:
z Where, dBi = dBd + 2.15
z The dBi indicates the energy concentration capability of the antennas with directions
(including omni antennas) as compared with that of the isotropic antennas. i stands for
isotropic.
z The dBd indicates that the energy concentration capability of the antennas with directions
(including omni antennas) as compared with that of the symmetrical dipole antennas. d
stands for dipole.
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Antenna Gain
z Relationship betweenAntenna Gain Ga, Horizontal Half PowerLobe Width and Vertical Half Power Lobe Width :
32400log10
aG
z One function of the antenna is concentrating energy, so if the radiation intensity in some
direction is strong; the radiation intensity in other direction is weak. Generally, the
radiation intensity in a direction can be enhanced through reducing the width of the lobes.
Another situation, when the antenna gain is certain, the antenna horizontal half power
angle is reversely proportional to the vertical half power angle.
z For example, there is an omni antenna. If the antenna gain is 11dBi, and the horizontal
half power angle is 360, the vertical half power angle is. Due to the difference of
antenna design and manufacturing, slight difference is present for the vertical half power
angle of the actual omni antenna. And such difference is determined by the focus and
implementation ways of the electrical design.
z When the antenna gain is small, the vertical half power angle and horizontal half powerangle are large; when the antenna gain is large, the vertical half power angle and
horizontal half power angle are small.
z In addition, the antenna gain depends on dipole quantity. The larger the dipole quantity,
the larger the antenna gain is, and the larger the antenna size. For example, for a 900MHz
omni antenna, if the antenna gain increases by 3dB, the antenna length doubles. Generally,
therefore, the gain of the omni antenna does not exceed 11dBi, and the antenna length
now is about 3 meters.
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Downtilt Angle
z Electric Downtilt and Mechanical Downtilt. Genarally, theformer is better, but more expensive.
1010oo
ElectricElectric 1010oo
MechanicalMechanical66oo
Electric +Electric +
44oo
MechanicalMechanical
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Others
Third-order Intermodulation product.
Two TRX use f1 and f2, both input power 43dBm. The Third-
order Intermodulation product is 2f1-f2 and 2f2-f1, the power ofwhich should be less than, for example, -150dBc or -107dBm.
IM3
The max average power capacity.
For example, a single carrier is 40W, one port input eight
carriers, the total input of the antenna is 320W. Therefore, thepower capacity of a single port must be greater than 320W.
Related to environmental temperature, typically tested under 50oC.
Power Capacity
For the antenna with multiple ports, such as dual polarization
antenna, the isolation between the ports for both transmission
and reception must be greater than 30dB
Port Isolation
DescriptionDescriptionParameterParameter
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Mechanical Specifications
z Input Connector Type
z Working Temperature
z Working Humidity
z Wind Load
z Size and Weight
Antenna size and weightz If all electric indicators are met, the antenna should be as small as possible in size and as light as
possible in weight for storage, transport, installation, and security purposes.
z Now carriers have higher requirements on antenna size, weight, and shape. Therefore, both
technical indicators and the previous non-technical factors must be emphasized in antenna
selection. Generally, the antenna installed in urban area should be small, light, and eye catching.
Wind loadingz The base station antenna must be installed on the top of high buildings and towers. In coastal
areas, where the wind is strong all the year around, so it is required that the antenna can work
normally against the wind at the speed of 36m/s and are not damaged when the wind speed
reaches 55m/s.
z The antenna itself can stand strong wind. In areas where the wind is strong, the antenna is
damaged mainly because the tower or the supporting bar is damaged.
Work temperatire and humidity
z The base station antenna works normally when environment temperature ranges -40C to +65C
and environmental relative humidity ranges from 0 to 100%.
Lightning protectionz All RF input ports of the base station antenna are required to be directly grounded through direct
current.
Three proof capabilityz The base station antenna must have three proof capability, that is, moisture proof, salt
atmosphere proof, and mildew proof. For the omni antenna, it can be installed in reverse direction
according to installation instructions and the three proof requirements.
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Contents
1. Antenna Fundamentals
2. Antenna Working Principle
3. Antenna Specifications
4. Antenna Selection
5. Electric Downtilt Antenna
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Overview
z The antenna selection is very important. The selection shouldconsider actual conditions, such as coverage requirement, traffic
volume, interference, and QoS.
z Antenna selection is closely related to coverage, so the antenna
application can be divided into four types according to
landforms or traffic distribution: Urban area,Suburban area,
Rural area, and Road area.
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Problem in Antenna Selection
z Landforms and Antenna Pattern.
Blind under tower.Blind under tower.
z Large Mechanical Downtilt.
DistortionDistortion -->>
z High Gain Antenna.
Size, Zero Point, Side LobeSize, Zero Point, Side Lobe
z Polarization.
Loss.Loss.
InterferenceInterference
z The antenna is selected only based on the covered traffic distribution, but little
consideration is given to the relationship between landforms and antenna pattern diagram.
For example, if all antennas used in a network are of the same type, when the antenna is
installed at a high position, the phenomenon of "blind under tower will be present
because the width of the beams in vertical plane is narrow.
z Too large antenna mechanical tilt angle results in the distortion of the pattern diagram. In
this case, coverage problem or interference problem will occur. Emulation shows that the
restrictions on tilt angles must vary in accordance with the antennas with different gains.
z Too much attention is focused on the high gain performance of the antenna but little
attention is given to its drawbacks. As a result, the gains of almost all the antennas used in
a network are quite high. A high gain antenna has many drawbacks, including large size,great weight, high side lobe, deep zero lobe, and narrow vertical beams.
z No consideration is given to the difference between the vertical polarization antenna and
dual polarization antenna in terms of application. The dual polarization antenna is selected
from the perspective of installation.
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Downtilt Planning (Cont.)
z Downtilt Angle decided by Half Power Lobe Width ,Antenna High H and Coverage Distance D.
2)arctan( +=
DH
According to the technical performance of the antenna, the antenna gain decreases slowly
within half power angle, but it decreases sharply beyond the half power angle, especially
for the upper lobe. Therefore, when the antenna tilt angle is considered, the scope
between the extension line of the half power angle to intersection point (point B) can be
taken as the actual coverage area of the antenna.
z This formula can calculate the coverage distance after the adjustment for tilt angle. Actual
results of on-site optimization projects show that this formula is of great significance.
However, the application of this formula meets limited conditions. It can be applied when
the tilt angle is 1.5 times greater than the half power angle, and the distance (D) must be
less than the distance calculated by the formula when no tilt angle is present. For the
width of vertical beams in the formula, it is provided in the specific antenna technical
indexes.
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Downtilt Planning
23010001565 degrees, 15 dBi
10308001565 degrees, 15 dBi
12405001565 degrees, 15 dBi
12355001565 degrees, 15 dBi
11305001565 degrees, 15 dBi
10255001565 degrees, 15 dBi
17402501565 degrees, 15 dBi
15352501565 degrees, 15 dBi
14302501565 degrees, 15 dBi
DowntiltDowntilt AngleAngle
(degree)(degree)
AntennaAntenna
Height (m)Height (m)
CellCellradiusradius
R(mR(m))
Vertical HalfVertical Half
Power AnglePower AngleAntenna TypeAntenna Type
z According to the table, when the cell radius is small, the coverage area cannot be effectively controlled even
through mechanically tilting the antenna. In this case, the coverage area can be controlled through lowering
the antenna height only. If it is hard for the antenna height to be lowered, the antenna electrical tilt together
with the antenna mechanical tilt must be used.
z The previous methods for calculating tilt angles are mainly applicable for the dense base station networking
with the distance within 1200 meters (that is, R = 800 meters) between stations.
z When the distance from the base station to the coverage target is greater than 800 meters, large area
coverage is still being emphasized. In this case, it is unnecessary for you to consider the effect of the vertical
half power angle when estimating the antenna tilt angle. Generally, the tilt angle now is 1 degree to 4
degrees.
z However, because the environment around the base station is rather complicated, the reflection caused the
nearby mountains, water surface, huge glass walls has an effect on antenna tilt angle. The reflection of this
kind will easily cause unexpected interference against the neighbor frequencies and time dispersion effect. In
addition, the shadow effect caused by building roofs, front dense buildings and mountains must be alsoconsidered. In actual networking, however, geographic environment, such as the barrier of high buildings and
mountains, around the base station can be used to control coverage area.
z When a network is implemented in a populated urban area, the major lobe of the antenna cannot be directly
parallel to the street, or waveguide effect will easily occur. In this case, it is rather hard to prevent cross
coverage. When a cell is required to cover the area above the antenna height, you can use a directional
antenna and uplift this antenna.
z The effect of the antenna back lobes must be also considered. Generally, the front-to-back ratio of the
antenna is about only 20dB, so the back lobes with strong signals will cause much interference against high
building coverage. As a result, it is recommended that electrical tilt antennas should be used in populated
urban areas, it reduce back lobes. In addition, the effect of the upper side lobe must also be considered.
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Urban Area
Sites are very dense in urban areas. The coverage area of each cell should be assmall as possible to reduce interference and enhance frequency reuse.
Consider the limited space in cities, DualPolarization Antenna is prefered.
Antenna Polarization
medium gain 15dBi (900MHz) and 15-18dBi (1800 MHz)
Antenna Gain
z Should be smaller value, 65typically.
z Proper selection can reduce interference
Horizontal Half PowerLobe Width:
RequirementRequirementParameterParameter
z Because a large number of base stations are distributed in urban areas, overlapping coverage and
frequency interference rises as serious problems in a network. To reduce the overlapping areas of
neighbor sectors and the interference between base stations, you can set the beam width of theantenna horizontal half power to a smaller value. Generally, antennas whose horizontal half power
beam width is 65 are selected.
z The base stations in urban areas are not required to cover a large area, so the antennas with
medium gain are recommended. Thus the antenna vertical beam can be wider, which can improve
the coverage quality within the areas to be covered. In addition, the size and weight of the antenna
with medium gain are small, which is helpful for installing the antenna and reducing cost. According
to present antenna specifications, antennas with a gain of 15dBi (900MHz) and 15-18 dBi (1800
MHz) are recommended in urban areas.
z
For the base stations on the outskirt of a city, if it is required to cover a large distance, you canselect the antennas with higher gains, such as 17dBi and 18dBi.
z In urban areas, to enhance frequency reuse rate and reduce cross interference, you can select the
shaped-beamed antenna with the first upper side lobe suppressed and the lower side lobe filled.
z Because space restriction is present in the antenna installation in urban areas, the dual polarization
antenna is recommended. And it is better to select the antenna with a smaller size when the
electrical specifications of the antennas are the same or nearly the same.
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Suburban Area
Because the environment is suburban areas are largely different from that of urban
areas, antennas used in suburban areas can be selected according to the required
coverage area.
Omni antennas are not recommended for smooth
expansion in the future. Antenna type
z 65 or 90 can be selected
z According to actual conditions.
Horizontal Half Power
Lobe Width:
RequirementRequirementParameterParameter
z The antennas whose horizontal half power beam width is 65 or 90 can be selected
according to actual conditions. If base stations are sparsely distributed, the antennas
whose horizontal half power beam width is 90 is first considered.
z If the base stations are densely distributed, the antennas are selected by referring to the
principles for selecting base station antenna in urban areas.
z Omni antennas are not recommended for the purpose of smooth expansion in the future.
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Rural Area
z If directional antenna, 90 is recommended . Horizontal Half Power
Lobe Width:
In rural areas, traffic volume is small and base station are sparsely distributed, so
some base stations are required to cover a large area.
When high site for wide coverage, zero point filling
is necessary. Zero Point
Omni Antenna is recommended.
If for wide coverage, high gain directional antennais required.
Antenna type
RequirementRequirementParameterParameter
z Considering the construction cost, you are recommended to select an omni antenna for
the base stations whose coverage area is small and traffic volume is low. However,
because the gain of the omni antenna is low, the coverage of an omni antenna is shorter
than that of a directional antenna. When the base station is required to cover a long
distance, the directional antenna must be selected to realize the coverage. Generally, a
high gain vertical polarization antenna whose horizontal half power beam width is 90
is recommended.
z One point needs to be noted. That is, if the base station antenna is installed at a high
position, but the area needs to be covered lies in a low location (the depression angle is
greater than 5), when an omni antenna is used, the kind with a preset tilt angle or
with zero point filling function are recommended to improve the coverage quality of this
area. In this case, the phenomenon of blind under tower and the signal fluctuation
caused by uneven coverage can be avoided.
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Road Coverage
z To cover the areas along railways and highroads, a directionalantenna with narrow beams can be selected.
z To cover the highroads and the villages scattered around the
highroads, an omni antenna can be selected.
z To cover highroads only, an 8-shaped antenna can be selected.
z To cover the highroads and the towns on one side of the
highroads, the 210antenna can be selected.
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Road Coverage (Cont.)
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Road Coverage
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Reference
zMoutain side, first consider the antennas with low gain and
wide vertical beams.
Directional
zMoutain top, first consider the antennas with zero point filling
function, and then consider the antennas with low gain.
Omni
Mountain
zFirst consider the 210 antennas, and then consider using the
directional antenna and omni antenna together.
Directional
+ Omni
zFirst select the 8-shaped antennas, it is preferred to have zero
point filling function.
Directional
Expressways
zSelect the antennas with zero point filling.Omni
zGenerally, select the 90 antennas.DirectionalPlains &
Rural
zGenerally, select the antennas with high gain; both electrical
and mechanical tilt antenna are ok.
DirectionalSuburban
zGenerally, select low or medium gains and preset electrical tilt
angle.
DirectionalUrban
ReferenceReferenceTypeTypeLandformLandform
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Contents
1. Antenna Fundamentals
2. Antenna Working Principle
3. Antenna Specifications
4. Antenna Selection
5. Electric Downtilt Antenna
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Contents
5. Electric Downtilt Antenna
1.1 Basics
1.2 Antenna system
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Electric Downtilt Antenna
z In Electric Downtilt Antenna, feeding network is used to adjustamplitude& phase of input signal from different path, so as to
form radiation beam with a certain shape.
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Classification
zz FETFET(Fixed Electric Downtilt)
Electric Downtilt is fixed
zz METMET(Mechanical Electric Downtilt)
Electric Downtilt is changed by knob orpulling bar
zz RETRET(Remote Electric Downtilt)
Electric Downtilt is changed by OMC.
Add RCU (Remote Control Unit) to MET.
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Control cableControl cable(DC+ control signals )(DC+ control signals )
Pulling barPulling bar
MET and RET
METMET
RadomeRadome
Pulling barPulling bar
RadomeRadome
RCURCU
RETRET
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Contents
5. Electric Downtilt Antenna
1.1 Basics
1.2 RET Antenna system
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RET Antenna System
BTSBTS
RCURCUSBTSBT
AntennaAntenna
OMCOMC
BSCBSC
BTBT
BTSBTS
RCURCUSBTSBT
AntennaAntenna
BTBT
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Component
z
RCU (Remote Control Unit) motor driving and controlling unit for antenna.
Receive and execute command from BTS, drive the motor which
drives the adjustable phase shifter, so as to change the downtilt.
z SBT(Smart Bias-Tee)
Abstract DC (power source) and controlling command from feeder.
Provide DC and controlling command for RCU.
z BT(Bias-Tee) Couple DC and controlling command into feeder.
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RCU
MotorMotor
Port 2 toPort 2 to
cascading RCUcascading RCUPort 1 toPort 1 to
SBTSBT
AntennaAntennaAntennaAntenna AntennaAntenna
BTSBTS
RCU
RCU
SBTSBT
RCU
RCU
Sector 1Sector 1
RCU
RCU
Sector 2Sector 2 Sector 3Sector 3
BTBT
z Port 2 is uesd when RCU is cascaded, where one SBT control several RCU.
z If several antenna use the same downtilt, RCU can be cascaded.
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BT
DC/OOKDC/OOK
RFRF
OOKOOK
DCDCRFRF
Port 1 to feeder/antennaPort 1 to feeder/antenna
Port 3 to DATU BoardPort 3 to DATU Board
RF signalRF signal DC signalDC signal OOK signalOOK signal
Port 2 to BTSPort 2 to BTS
Bias TeeBias Tee
z DATU board give the controlling command for Antenna.
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SBT
Smart Bias TeeSmart Bias Tee
RFRFsignalsignal
DCDCsignalsignal
OOKOOKsignalsignal
Port 1 to AntennaPort 1 to AntennaPort 2 to FeederPort 2 to Feeder
Port 3 to RCUPort 3 to RCU
RS485RS485signalsignal
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Summary
z In this course, we have learned:
Antenna working principles
Important Antenna specifications
Choose correct type of antenna in different situation
Electric Downtilt Antenna
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