gb_bt42_e1_0 antenna system introduction-47.doc

7/25/2019 GB_BT42_E1_0 Antenna System Introduction-47.doc

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GB_BT42_E1_0 Antenna System Introduction

Course Objectives

Understand antenna principles

Understand technical parameters of antenna

Grasp antenna selection methods


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Contents

1 Antenna Overvie!"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""1

1.1 Antenna Development Overview........................................................................................................1

1.2 Antenna Radiation Principles..............................................................................................................2

1.2.1 Electromagnetic Wave Radiation of Electric Dipoles..............................................................2

1.2.2 alf!Wave Do"#let...................................................................................................................$

1.$ Antenna %tr"ct"re and &'pes...............................................................................................................(

1.$.1 Directional Panel Dipole!Arra' Antenna.................................................................................(

1.$.2 Omni!Directional %eries!)eed Dipole Antenna.......................................................................*

2 Antenna Tec#nica$ %arameters""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""&

2.1 Antenna Gain.......................................................................................................................................+

2.2 Radiation Pattern...............................................................................................................................1,

2.$ -o#e Width.........................................................................................................................................11

2.$.1 oriontal -o#e Width...........................................................................................................11

2.$.2 /ertical -o#e Width................................................................................................................12

2.( )re0"enc' and.................................................................................................................................12

2. Polariation 3ode..............................................................................................................................1$

2.4 Downtilt 3ode...................................................................................................................................1(

2.* Antenna )ront!to!ac5 Ratio............................................................................................................1

2.6 Antenna 7np"t 7mpedance 8in...........................................................................................................1

2.+ Antenna /%WR..................................................................................................................................14

2.1, %ide -o#e %"ppression and 9"ll )ill...............................................................................................1*

2.11 &hird!Order 7ntermod"lation...........................................................................................................16

2.12 7nter!Port 7solation...........................................................................................................................16


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' Antenna En(ineerin( %arameters"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""1&

$.1 Antenna Aim"th...............................................................................................................................1+

$.2 Antenna eight..................................................................................................................................2,

$.$ Antenna Downtilt...............................................................................................................................22

4 Antenna Cate(ories"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""2)

) Antenna A**$ication Scenarios""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""'1

.1 Dense Ur#an Area..............................................................................................................................$1

.2 :ommon Ur#an Area ;&ownseeping Pole /ertical.............................................................................................................$+

*.1.2 -ightning Protection...............................................................................................................$+

*.1.$ Diversit' Reception................................................................................................................(,

*.1.( Antenna 7solation....................................................................................................................(1

*.2 Antenna 7nstallation at 7ron &ower....................................................................................................(1

*.$ %"mmar'............................................................................................................................................(2


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1 Antenna Overview

&his chapter introd"ces antenna radiation principles? t'pes? technical development? and

development trend.

1.1 Antenna Development Overview

7n cell"lar mo#ile comm"nication s'stem? antenna f"nctions as the converter #etween

the comm"nication e0"ipment circ"it signal and the radiating electromagnetic wave.

&he cell"lar mo#ile comm"nication re0"ires relia#le comm"nication #etween #ase

station and 3%? which p"ts special re0"irement on antenna. &he R) signal power

which is o"tp"tted #' the radio transmitter is sent to antenna thro"gh feeder ca#le? and

then radiated in the form of electromagnetic wave #' antenna. &he electromagnetic

wave is received ;onl' a ver' small part of the power< #' antenna after arriving at the

destination? and then is sent to the radio receiver thro"gh feeder ca#le. &herefore?

antenna is an important radio device for sending and receiving the electromagnetic

wave. %'stem comm"nication performance is affected #' man' factors incl"ding

antenna gain? coverage direction? #eam? availa#le driving power? antenna

config"ration? and polariation mode.

Tec#no$o(y and mar.et situations o/ C#inese antenna enter*rises

According to statistics? the mar5et share of domestic antenna prod"cts acco"nts for

onl' 2,@ of the total antenna mar5et shares in :hina in the following fields

:ivil #ase station antenna? in which technologies of mo#ile comm"nication? spread

spectr"m? and microwave comm"nication are applied

7ntelligent antenna

l"etooth antenna

&ill the first half of 2,,2? there were over 1,, domestic antenna enterprises in :hina.

owever? according to the total amo"nt of prod"ction and sales? onl' a few enterprises

owned 2,, pl"s emplo'ees and $, million pl"s R3 operating income.

Advanta(es o/ internationa$ antenna enter*rises

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7nternational antenna enterprises own rich f"nds? enBo' well!5nown #rands? and have

plent' of h"man reso"rces and advanced technologies. 3an' of them #oast a histor' of

more than , 'ears and have an ann"al operating income of more than 2 #illion dollars.

After :hina Boined World &rade Organiation ;W&O


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Error se t#e ome tab to a**$y1 to t#e te3t t#at you !ant to a**ear #ere" Error se t#e ome tab to a**$y

1 to t#e te3t t#at you !ant to a**ear #ere"

)ig"re 1.2!1 Relation #etween Dipole Angle and Electromagnetic Radiation 7ntensit'

&he following two points sho"ld #e noticed

When the wire length is far shorter than the wavelength ? the radiation is wea5.

When the wire length increases to #e similar to the wavelength ? the c"rrent in the

wire increases greatl' and forms strong radiation.

1.2.2 Half-Wave Do!let

&he do"#let is a classical and most commonl' "sed antenna. A single half!wave

do"#let can #e "sed independentl' or "sed as the feed of para#olic antenna. Also?

m"ltiple half!wave do"#lets can #e com#ined to form the antenna arra'.

oteDo"#let is also called #alanced dipole somewhere in this doc"ment.

Dipole of which the two arms have the same length is called do"#let. )or half!wave

do"#let? each arm is 1=( long and the total length is 1=2 ? as shown in)ig"re 1.2 !2.

)ig"re 1.2!2 alf!Wave Do"#let

esides? there is also a heterogeneo"s half!wave do"#let? which can #e considered as

folding the f"ll!wave do"#let into a narrow and long rectangle in which the two points

of the f"ll!wave do"#let are overlapped. &he narrow and long rectangle is called folded

dipole? as shown in )ig"re 1.2 !$.

ote&he folded dipoles length is also 1=2 ? that is wh' it is also called half!wave folded dipole.

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G&(2E1, Antenna %'stem 7ntrod"ction

)ig"re 1.2!$ alf!Wave )olded Dipole

1." Antenna #trctre and $%pes

1.".1 Directional Panel Dipole-Arra% Antenna

&he directional panel antenna is the most commonl' "sed antenna in #ase station

applications. 7t enBo's the following advantages

igh antenna gain

Good sector pattern

%mall #ac5 lo#e

Eas' control of vertical!plane pattern depression angle

Relia#le encaps"lation

-ong service life

)ig"re 1.$ !(shows the antenna appearance.

)ig"re 1.$!( Directional Panel Antenna Appearance

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1.".1.1 Panel Antenna Hig& 'ain (ormation

)ig"re 1.$! Arranging 3"ltiple alf!Wave Dipoles to )orm a /ertical -inear Arra'

)ig"re 1.$!4 Adding Reflection Panel at One %ide of -inear Arra' to Realie oriontal Orientation

At present? the directional antenna design mainl' adopts the panel dipole arra'

str"ct"re. &he following two t'pes of dipoles are often "sed

alanced dipole

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3icrostrip dipole

1.".1.2 )alanced Dipole

7n a standard half!wave do"#let? an additional dipole is added to red"ce the dipoles

height a#ove the gro"nd? which red"ces the antennas thic5ness.

)ig"re 1.$!* :om#ining 3"ltiple alf!Wave Dipoles to )orm Directional Panel Antenna

1.".1." *icrostrip Dipole

&he microstrip dipole is a variation of the half!wave dipole. 7t radiates according to the

1=( transmission line principle.

)ig"re 1.$!6 :om#ing 3"ltiple 3icrostrip Dipoles to )orm Directional Panel Antenna

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1.".1.+ Antenna Dipole Arra% #trctre

)ig"re 1.$!+ Dipole Arra' %tr"ct"res of Panel Antenna

1.".2 Omni-Directional #eries-(eed Dipole Antenna

&he omni!directional antenna realies radiation gain com#ination and enhancement

thro"gh the m"lti!half!wave!dipole series!feed mode.

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)ig"re 1.$!1, Omni!Directional Antenna %eries!)eed Dipole %tr"ct"re

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2 Antenna $ec&nical Parameters

&his chapter eCplains concepts of antenna technical parameters and their applications

in networ5 design.

2.1 Antenna 'ain

Antenna gain is an important parameter for antenna s'stem design. 7ts definition is

related to the half!wave dipole or the f"ll!wave antenna. )or omni!directional radiator?

it is ass"med that the radiation power is same in all directions. &he antenna gain in a

direction is e0"al to the field intensit' it generates divided #' the intensit' generated #'

the omni!directional radiator in this direction.

&he "nit of antenna gain is dd or di. di represents the reference val"e of field

intensit' in the direction with the maCim"m radiation? relative to the omni!directional

radiator ;as shown in )ig"re 2.1 !11 ;middle


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2.2 Radiation Pattern

&he #ase station radiation pattern incl"des the following two t'pes

Omni!directional radiation pattern.

Directional radiation pattern.

)ig"re 2.2!12 )ield 7ntensit' Distri#"tion for Omni!Directional Antenna and Directional Antenna

As shown in )ig"re 2.2 !12?the left fig"res are horiontal cross!section pattern and

three!dimensional radiation pattern of the omni!directional antenna. &he right fig"res

are horiontal cross!section pattern and three!dimensional radiation pattern of the

directional antenna.

&heoreticall'? the omni!directional antenna has the same radiation intensit' in all

directions in the same horiontal plane. 7t is s"ita#le for the omni!directional cell.

As shown in)ig"re 2.2 !12? the red part represents the metal reflection panel in

the directional radome? which ma5es the antenna radiation in the horiontal plane

directional. &he directional antenna is s"ita#le for sector coverage.

2." ,o!e Widt&

2.".1 Horiontal ,o!e Widt&

)or omni!directional antenna? the horiontal lo#e width is $4,H ;as shown in )ig"re

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2.$ !1$;right


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2.".2 ertical ,o!e Widt&

)ig"re 2.$!1 Antenna /ertical -o#e $ d Width

&he width of antenna vertical lo#e $d? which is often 1,H? is closel' related to the

antenna gain and the horiontal lo#e $d width. Us"all'? with the same antenna design

technolog' and the same antenna gain? the wider the horiontal lo#e is? the narrower

the vertical lo#e $d is.

&he narrow width of vertical lo#e $d might ca"se man' coverage holes. As shown in

)ig"re 2.$ !1?for the two non!downtilt antennas with the same height? the red one

;with wide vertical lo#e< has a coverage hole range of OJ while the #l"e one ;with

narrow vertical lo#e< has a coverage hole range of OJ.

&herefore? in order to g"arantee good coverage and avoid coverage hole? it is advised

to select the antenna with wide vertical lo#e $d width? on the premise of having the

same antenna gain.

2.+ (re/enc% )and

)or #ase stations? the wor5ing #and of the selected antenna m"st incl"de the re0"ired

#and.

G%3 +,, s'stem d"al #and antennas with wor5ing #and of 6+, 3 +4, 3?

6*, 3 +4, 3? 6,* 3 +4, 3? and 6+, 3 166, 3 can #e

selected.

:D3A 6,, s'stem antennas with wor5ing #and of 62( 3 6+( 3 can #e

selected.

:D3A 1+,, s'stem antennas with wor5ing #and of 16, 3 1++, 3 can

#e selected.

7n order to red"ce the o"t!of!#and interference? it is advised to select antenna of which

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the #andwidth B"st satisfies the #and re0"irement.

2.0 Polariation *ode

At the #ase station? antennas often adopt the linear polariation mode? as shown in

)ig"re 2. !14.Us"all'? the single!polaried antenna adopts vertical polariation mode

and the d"al!polaried antenna adopts (d"al!linear polariation mode.

)ig"re 2.!14 :ommon Polariation 3odes for Antenna

A d"al!polaried antenna consists of two perpendic"lar polaried antennas which are

encaps"lated in the same radome as shown in )ig"re 2. !1*.7t can red"ce the n"m#er

of antennas greatl'? simplifies the antenna installation? and red"ce the cost and

occ"pied space of the antenna.

)ig"re 2.!1* D"al!Polaried Antennas

2. Downtilt *ode

&o avoid coverage hole near the #ase station and red"ce the interference on other

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adBacent #ase stations? it is advised not to mo"nt the antenna in ver' high places. Also?

the downtilt mode is re0"ired.

As shown in )ig"re 2.4 !16? the antenna mo"nted in low place ;the 'ellow one< has a

coverage hole range of OJK while the antenna with downtilt ;the green one< has a

coverage hole range of OJ. &he coverage hole range of #oth are smaller than that of

the non!downtilt antenna mo"nted in high place ;the #l"e one? the coverage hole range

is OJ


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)or electrical downtilt? the downtilt range is comparativel' large ;might #e larger than

1,I


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have a good impedance matching with the feeder ca#le.

2.7 Antenna #WR

&he antenna /oltage %tanding Wave Ratio ;/%WR< is the indeC which indicates the

matching #etween antenna feeder and #ase station ;transceiver


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)ig"re 2.1,!2, :overage :omparison #efore and after 9"ll )ill 7s Performed

Antenna n"ll!fill val"e

F ;the first downward n"ll amplit"de val"e = amplit"de val"e in the maCim"m radiation

direction


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2.12 5nter-Port 5solation

)or m"lti!port antenna? the isolation #etween different ports m"st #e larger than $, d.

)or eCample? the isolation m"st #e larger than $, d in the following cases

etween the two polaried ports of d"al!polaried antenna

etween the two fre0"enc' #and ports of o"tdoor d"al!#and antenna

etween the fo"r ports of d"al!#and d"al!polaried antenna

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" Antenna Engineering Parameters

&his chapter introd"ces antenna engineering parameters and their infl"ences on

coverage? and the wa's to improve the networ5 performance #' "sing these parameters.

".1 Antenna Aimt&

&he electromagnetic field of antenna radiation is a graph which is distri#"ted in fiCed

distance according to the angle coordinate. &he graph is called antenna pattern.

&he antenna pattern which is eCpressed #' the radiation field intensit' is called

field intensit' pattern.

&he antenna pattern which is eCpressed #' the power densit' is called power

pattern.

&he antenna pattern which is eCpressed #' the phase is called phase pattern.

&he antenna pattern is a three!dimensional graph. 7t is often eCpressed in the form of

directional patterns in two perpendic"lar main planes? which are called vertical

directional pattern and horiontal directional pattern. &here are two t'pes of horiontal

directional pattern omni!directional!antenna!#ased and directional!antenna!#ased.

Directional!antenna!#ased horiontal pattern also has man' t'pes? s"ch as heart!shaped

t'pe and 6!shaped t'pe.

&he directional characteristic of an antenna is ca"sed #' changes in the dipole arra'

and the dipole feeding phase. &heoreticall'? it is similar to the optical interference

effect? th"s energ' in some directions might increase while energ' in some other

directions might decrease? forming the lo#e ;or #eam< and n"ll. &he lo#e with the

strongest energ' is called the main lo#e? the "pward=downward lo#e with the second

strongest energ' is called the first side lo#e? and so on. Directional antenna has the

#ac5 lo#e.

&he antenna aim"th adB"stment is ver' important for improving comm"nication

networ5 0"alit'. Acc"rate antenna aim"th g"arantees normal networ5 r"nning and that

the act"al coverage is the same as the eCpected coverage. On the other hand? adB"sting

the antenna aim"th according to the traffic and act"al networ5 sit"ation can #etter

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optimie the c"rrent mo#ile comm"nication networ5.

According to the ideal cell"lar mo#ile comm"nication model? signals at the #o"ndar'of a cell are m"t"all' complementar'. 7n c"rrent G%3 s'stems ;here? mainl' refers to

ER7:%%O9 e0"ipment


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&ransmission power

Antenna gain

)eeder ca#le loss

Antenna height

Wor5ing #and

Distance #etween the transmitter and the receiver

All propagation models are related to the height of transmitting antenna and the

receiving antenna. &herefore? the antenna height has an important infl"ence on the path

loss.

&he coverage distance from the transmitting end to the receiving end is as follows

( ) ( ) (1

(1

21

(1

RSD

LGGhhP

P

trtr

r

t

rP Receiving power

tP

&ransmission power

rh Antenna height at the receiving end

th

Antenna height at the transmitting end

rG Receiving antenna gain

tG

&ransmitting antenna gain

L

Path loss correction factor

With fiCed transmitter and receiver parameters? the coverage area is in direct proportionto the antenna height and antenna gain.

D"ring the earl' G%3 networ5 constr"ction? there are not so man' sites? and antennas

are installed in high places in order to have good coverage. With the rapid development

of mo#ile comm"nication? the n"m#er of sites increases greatl'? there are a#o"t one

site ever' ,, m in "r#an area. &herefore? the coverage area of a site m"st #e red"ced

#' lowering the antennaM otherwise? the networ5 0"alit' will #ecome worse? with the

following negative infl"ences

&raffic is not e0"alied.

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7f the antenna is too high? then the sites coverage area will #ecome too large. 7t

ca"ses heav' traffic at this siteM meanwhile? the adBacent sites coverage area

#ecomes small and has low traffic. 7n other words? the traffic is not e0"alied.

7ntra!s'stem interference

7f the antenna is too high? then cross!site radio interference will #e generated?

incl"ding co!fre0"enc' interference and adBacent!fre0"enc' interference. 7t ca"ses

pro#lems s"ch as call drop? cross tal5? and noise? and the entire comm"nication

networ5 0"alit' degrades.

7solated island effect

&he isolated island effect is relevant to site coverage. 7f a site covers water area or

mo"ntaino"s area? then? on the premise of the original coverage area not #eing

changed? the remote part of the coverage area #ecomes an isolated island d"e to

reflection #' water or mo"ntain. 3oreover? adBacent sites? to which handover

co"ld #e performed #efore? now have no handover relationships with the site.

When a handset occ"pies signal in the isolated island? call drop often occ"rs d"e to

no handover relationship.

"." Antenna Downtilt

&hro"gh adB"sting the antenna main lo#es downtilt to a certain angle? the power level

of adBacent site can #e red"ced? which then red"ces the interference.

&he antenna downtilt is related to the following parameters

Antenna height

:overage radi"s

Antenna vertical lo#e

Electrical downtilt

With the same coverage radi"s? the higher the antenna is? the larger the antenna

downtilt is. 7n other words? with the same antenna height? the smaller the coverage

radi"s is? the larger the antenna downtilt is.

7nterference tends to eCist in "r#an area with man' sites. 7n order to ma5e most energ'

radiate in the coverage area and red"ce interference on adBacent cells? it is re0"ired to

ma5e the half!power point on the antenna main lo#e to aim at the coverage area edge.

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&he calc"lation form"la of antenna downtilt is as follows

F arctg ;2=-< ;16,=< L ;=2< T e

7n s"#"r#? co"ntr'? road? or sea area? to ma5e the coverage as remote as possi#le?

red"ce the initial downtilt? and ma5e the point on antenna main lo#e with the maCim"m

gain to aim at the coverage area edge. &he calc"lation form"la of antenna downtilt is as

follows

F arctg ;=-< ;16,=< L ;=2< T e

7n the a#ove two form"las

&he initial mechanical downtilt of antenna? the "nit is degree ;I


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+ Antenna Categories

&here are vario"s t'pes of antennas? which are s"ita#le for different sit"ations.

Antennas can #e categoried according to different standards

' "sage

:omm"nication antenna? television antenna? radar antenna? and so on

' wor5ing #and

%hort!wave antenna? s"per!short!wave antenna? microwave antenna? and so on

' appearance

-inear antenna? panel antenna? and so on

' direction

Omni!directional antenna? directional antenna? and so on

At present? the wor5ing #and? gain? and front!to!#ac5 ratio of vario"s t'pes of antennas

are similar? and all satisf' the networ5 performance re0"irement. &his chapter mainl'

anal'es the a#ove antennas according to antenna downtilt infl"ence on the antenna

pattern and the radio networ5.

Omni5-irectiona$ Antenna

)or omni!directional antenna? the radiation is evenl' distri#"ted in $4,H in the

horiontal pattern. 7n the vertical pattern? the radiation is represented in the form of

#eam with certain width. Us"all'? the smaller the lo#es width is? the larger the antenna

gain is. &he omni!directional antenna is often applied in sites which are designed for

large cells in s"#"r#? with large coverage area.

-irectiona$ Antenna

)or directional antenna? the radiation is distri#"ted within a certain range of angles in

the horiontal pattern. 7n the vertical pattern? the radiation is represented in the form of

#eam with certain width. %imilar to the omni!directional antenna? the smaller the lo#es

width is? the larger the antenna gain is. &he directional antenna is often applied in sites

which are designed for small cells in "r#an area? with small coverage area? high

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s"#scri#er densit'? and high fre0"enc' "tiliation ratio.

Different t'pes of sites are esta#lished according to different networ5ing re0"irements?and different site t'pes re0"ire different antenna t'pes according to technical

parameters mentioned previo"sl'.

)or omni!directional site? the omni!directional antenna with the same gain at

vario"s horiontal directions is selected.

)or directional site? the directional antenna with different gain at different

horiontal directions is selected.

7n "r#an area? the antenna with a horiontal #eam width of 4I is selected.

7n s"#"r#? the antenna with a horiontal #eam width of 4I? +,I? or 12,I

;according to act"al site config"ration and geographical environment< is selected.

7n r"ral area? the omni!directional antenna that realies large coverage area is

preferred d"e to its econom'.

6ec#anica$ Antenna

)or mechanical antenna? the antenna downtilt is adB"sted mechanicall'.

After the mechanical antenna is installed verticall' on the gro"nd? the downtilt can #e

changed #' adB"sting the #rac5et position on the rear side of antenna. D"ring the

process? the amplit"de val"es of vertical component and horiontal component of the

antenna do not change altho"gh the main lo#es coverage changes. &herefore? the

antenna pattern tends to #e distorted.

7t is fo"nd thro"gh practical cases that

&he #est downtilt for mechanical antenna is 1I I.

When the downtilt changes #etween I 1,I? the antenna pattern is slightl'

distorted? #"t the distortion is not serio"s.

When the downtilt changes #etween 1,I 1I? the antenna pattern distortion is

large.

When the downtilt reaches 1I? the shape of antenna pattern changes greatl' ;from

the pear!shape to spindle!shape


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D"ring the dail' maintenance? the s'stem sho"ld #e powered off #efore adB"sting the

mechanical antenna downtilt? and s'stem monitoring can not #e performed d"ring the

antenna downtilt adB"stment. 3aintenance personnel sho"ld clim# to the place where

the mechanical antenna is installed and perform the downtilt adB"stment. 3oreover? the

mechanical antenna downtilt is a theoretical val"e calc"lated thro"gh the em"lation

software? and has some difference from the #est downtilt in practice. &he step in

mechanical antenna downtilt adB"stment is 1I? and the third!order intermod"lation

val"e is !12, dc.

E$ectrica$ Antenna

)or electrical antenna? the antenna downtilt is adB"sted thro"gh changing the phase ofantenna dipoles in the same antenna arra'. D"ring the process? the amplit"de val"e of

vertical component and horiontal component of antenna are changed? which ca"ses

the com#ined field intensit' and the antenna downtilt to change. eca"se the field

intensit' in all directions of the antenna increases or decreases sim"ltaneo"sl'? it

g"arantees that the antenna pattern does not change m"ch after the antenna downtilt is

changed. &he coverage distance in the main lo#e direction is shortened? and the

coverage area within the sector of service cell is red"ced witho"t generating

interference.

7t is fo"nd thro"gh practical cases that

When the downtilt changes #etween 1I I? the antenna pattern is similar to that of

the mechanical antenna.

When the downtilt changes #etween I 1,I? the antenna pattern is improved

compared with that of the mechanical antenna.

When the downtilt changes #etween 1,I 1I? the antenna pattern change is larger

than that of the mechanical antenna.

When the downtilt reaches 1I? the antenna pattern differs greatl' from that of the

mechanical antenna. &he shape of antenna pattern does not change m"ch. &he

coverage distance in the main lo#e direction #ecomes m"ch shorter? and the entire

antenna pattern is within the sites sector. 7ncreasing the downtilt helps to red"ce

the coverage area within the sector witho"t ca"sing interference.

&herefore? the electrical antenna can red"ce the call loss and interference.

3oreover? the electrical antenna allows downtilt adB"stment d"ring the s'stem r"nning?

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th"s real!time monitoring can #e performed for the downtilt adB"stment. &he step in

electrical antenna downtilt adB"stment is ,.1I? which g"arantees precise adB"stment.

&he third!order intermod"lation val"e is !1, dc? with a $, dc difference from the

mechanical antenna. All these factors help to eliminate adBacent!fre0"enc' interference

and sp"rio"s interference.

-ua$5%o$ari7ed Antenna

A d"al!polaried antenna contains two perpendic"lar polaried antennas ;L(I and

!(I< which sim"ltaneo"sl' wor5 in the transceiving d"pleC mode. 7t saves the n"m#er

of antennas for single directional site.

Generall'? a directional site ;three sectors< in G%3 s'stem re0"ires nine antennas? each

sector "sing three antennas ;space diversit'? one for transmitting and two for

receiving


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antenna is "sed? the antenna pattern #ecomes distorted when the downtilt is larger

than I and the distortion #ecomes worse when the downtilt eCceeds 1,I. &h"s it is

advised to "se the electrical antenna or d"al!polaried antenna in areas with heav'

traffic.

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0 Antenna Application #cenarios

&his chapter eCplains the coverage area t'pes and radio environment with pict"res of

practical application scenarios.

0.1 Dense :r!an Area

)ig"re .1 !21shows the application scenarios in dense "r#an area.

)ig"re .1!21 Dense Ur#an Area

0.2 Common :r!an Area ;$ownseeping Pole ertical

7f the pole is #ent or slanting? it might directl' infl"ence the directional antenna

downtilt precision and the omni!directional antenna receiving effect.

&herefore? it sho"ld #e ens"red that the pole on which the antenna is installed is

vertical. Use the pl"mmet to chec5 the antenna verticalit' and ens"re that the omni!

directional antenna is perpendic"lar to the gro"nd. )or directional antenna? the downtilt

is meas"red with the downtilt tester? and the mechanical downtilt sho"ld incl"de the

slanting angle or #ending angle of the pole.

.1.2 ,ig&tning Protection

&o protect the site ;especiall' the antenna s'stem< in mo"ntaino"s area from lightning

attac5? the lightning protection design m"st #e considered in antenna installation to

ens"re operation safet' and normal s'stem r"nning.

)or a complete lightning protection device? the following factors sho"ld #e considered

-ightning rod design to control the lightning attac5 point to avoid lightning attac5

at dangero"s places.

Good gro"nding str"ct"re and appropriate gro"nding resistance val"e.

Good down lead.

Relia#le e0"ipotential #onding? to avoid high!voltage lightning attac5.

Preventing from leading in lightning high!voltage s"rge.

&he R) antenna is installed within the (I protection range of the lightning rod? which

is connected with the down lead thro"gh relia#le soldering. &he down lead is made of

(, mm (, mm galvanied flat steel. &he distance #etween the down!lead connection

point and the gro"nding inlead in the gro"nd net sho"ld #e not less than 1, m.

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.1." Diversit% Reception

7n mo#ile comm"nication? the m"ltipath transmission ca"ses rapid signal fading? and

the fading signal level range can reach $, d? approCimatel' 2, times per second. &he

antenna diversit' technolog' can greatl' red"ce the signal fading eCtent and improve

the lin5 0"alit'. &he distance #etween antennas is decided #ased on the principle that

#ranch signal fading of all antennas are "ncorrelated or approCimatel' "ncorrelated.

&he signal independence is eval"ated #' the coefficient of correlation of #ranch

signals. &he coefficient of correlation of the receiving signal m"st #e less than ,.*.

-iversity distance /or sin($e5*o$ari7ed antenna

&he distance #etween horiontal diversities is 2, V? and the distance #etween vertical

diversities is 1 V. On the premise of not changing the distance #etween antennas? the

correlation #etween antenna receiving signals can #e red"ced #' increasing the antenna

height. &he gain of horiontal space diversit' is a#o"t $ d d? and the gain of

vertical space diversit' is a#o"t 2 d ( d. &he horiontal space diversit'

performance is #etter than the vertical space diversit' performance.

7n practical applications? the minim"m distance #etween horiontal space diversities of

two single!polaried antennas in the same sector m"st #e larger than or e0"al to 1, V.

&a#le *.1!1 Distance #etween Antenna oriontal Diversities

Wor5ing

fre0"enc'

Distance #etween oriontal %pace

Diversities

Distance #etween /ertical %pace

Diversities

3inim"m /al"eRecommended

/al"e3inim"m /al"e

Recommended

/al"e

(, 3 4.* m 1$ m 1, m

6,, 3 $.4 m * m .( m

1.+ G 1.4 m $ m 2.( m

2 G 1. m $ m 2.$ m

-iversity o/ dua$5*o$ari7ed antenna

)or two antennas at the same place of which the polariation directions are

perpendic"lar? the signal fading is m"t"all' "ncorrelated. &he d"al!polaried antenna

"ses this feat"re to realie diversit' reception. 7n other words? after installing (I

polaried antennas on the receiving!end antenna? polariation diversit' can #e realied

for the two wa's of received signals of which the signal fading is m"t"all'

"ncorrelated.

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&he polaried diversit' antenna o#tains independent fading signal thro"gh the

perpendic"lar polaried antenna? th"s the space diversit' is not re0"ired. )or sites in

"r#an area? it is diffic"lt to install antennas that satisf' the space diversit' distance

re0"irement. &h"s the polariation diversit' #ecomes an important approach to realie

diversit' reception.

7t sho"ld #e noticed that the distance #etween two single!polaried antennas is the

vertical distance #etween two parallel lines in the antenna direction? not the direct

distance #etween the two antennas. )or d"al!polaried antenna? the distance

meas"rement is not re0"ired.

.1.+ Antenna 5solation

Antenna isolation within the same s'stem demands that the distance #etween antennas

in different sectors of the same s'stem m"st #e larger than ,.4 m. 7n practical

applications? the 1!meter antenna pole arm is installed on the arm #rac5et? and the

antenna is installed on the antenna pole? as shown in )ig"re *.1 !24.

)ig"re *.1!24 &hree!Dimensional Diagram and Planform

.2 Antenna 5nstallation at 5ron $ower7n practical applications? the antenna is mo"nted on the arm over 1 m a#ove the iron

tower platform. &he vertical distance #etween antennas on different platforms is larger

than 1 m.

&he following cases sho"ld #e noticed d"ring antenna installation on the iron tower

7nstalling directional antenna at the iron tower

&o red"ce the iron tower infl"ence on the antenna pattern? ma5e the distance

#etween the directional antenna center and the iron tower to #e V=( or $=( V. 7t

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helps to get maCim"m directions.

7nstalling omni!directional antenna at the iron tower

&o red"ce the iron tower infl"ence on the antenna pattern? ens"re that the iron

tower is not the antenna reflector? and the minim"m distance #etween antenna and

an'where of the iron tower m"st #e larger than V.

3"ltiple antennas sharing the same iron tower

&o red"ce the co"pling interaction and m"t"al infl"ences #etween transceiving

antennas of different networ5s? increase the isolation #etween antennas. 7t can #e

realied #' increasing distance #etween antennas. /ertical installation is preferred

in this case.

." #mmar%

Distance from the iron tower platform N 1 m

Distance #etween antennas

Diversit' reception antenna within the same cell N $ m

Omni!directional antenna ;horiontal distance

gb_bt42_e1_0 antenna system introduction-47.doc

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