24 CDMA Antenna System

7/29/2019 24 CDMA Antenna System

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CDMA RF Planning Unit 4




¾BTS Antenna SystemStructure

BTS Antenna Specificationand Meanings

Antenna Types and Trends

Main Content




Cabinet

Antenna

7/16 Din Connector

7/8“ Cable

Grounding

1/2“ Jumper

EMPGrounding clip

Grounding bar

1/2 Clamp

Tower TopAmplifier

7/8“ Cable

Machine house

1/2“ Jumper

BTS Antenna System Structure

If very short, can be elidedIf >50metersUse 5/4 “ Cable

Only for long

Distance coverageapplication

Z1



幻灯片 3

Z1 ZJT, 2006-2-20


http://slidepdf.com/reader/full/24-cdma-antenna-system 5/57 The information contained in the file is solely property of ZTE corporation. Any kind of disclosing without permission is prohibited.

ZTE University univ.zte.com.cnuniv.zte.com.cnuniv.zte.com.cn

BTS Antenna SystemStructure

¾BTS Antenna Specificationand Meanings


Main Content


http://slidepdf.com/reader/full/24-cdma-antenna-system 6/57 The information contained in the file is solely property of ZTE corporation. Any kind of disclosing without permission is prohibited.ZTE University univ.zte.com.cnuniv.zte.com.cnuniv.zte.com.cn

What Is The Antenna?

Blah blah

blahblah

• An antenna is just a passive conductor carrying RF current:– RF power causes current to flow in the antenna

– current flowing radiates electromagnetic fields

– electromagnetic fields cause current in receiving antennas



Electrical properties¾ HalfwaveDiopleAntenna¾

Operation Frequency Band¾ Antenna Gain¾ Radiation Pattern¾ Horizontal/Vertical beamwidth

Radiation Pattern¾ Downtilt¾ Front/Back Ratio¾ SidelobeSuppression and Null

Filling¾ Input Impedance¾ VSWR¾ Polarization¾ Isolation

Mechanical properties¾ Size¾

Weight¾ Radomematerial¾ Appearance and color¾ Working temperature

¾ Storage termperature¾ Windload¾ Connector types¾ Package Size

¾ Lightening

Antenna Specification and Meaning



Electrical Properties

Antenna should be testedStrictly in lab before selling.We make the choice according

To our requirement。

Antenna should be testedStrictly in lab before selling.

We make the choice according To our requirement。



Wavelength

1/2 Wavelength

1/4 Wavelength

1/4 Wavelength

1/2 Wavelength

Dipole

1900MHz ：157mm

800MHz ：375mm

Antenna Foundation---halfwavedipole

Halfwavedipole is a classical and very popular antenna. It can be usedindependently , and also multiple dipoles can be combined to a antennamatrix, to be used together.

Halfwavedipole has two symmetrical arms, one is ¼ wave length of the

Radio signal. All together, they are half wave.

Halfwavedipole is a classical and very popular antenna. It can be usedindependently , and also multiple dipoles can be combined to a antennamatrix, to be used together.

Halfwavedipole has two symmetrical arms, one is ¼ wave length of theRadio signal. All together, they are half wave.

AntennaFoundation



Antenna Foundation---halfwavedipole

TX RX

Width of banddenotes current

magnitude

Zero currentat each end

Maximum current

at the middleCurrent induced inreceiving antennais vector sum of

contribution of every

tiny搒 lice?of radiating antenna

each tinyimaginary搒 lice

of the antennadoes its share

of radiatingUsingadvancedmathematics,

the radiationpattern of dipole can bedrawed.

Usingadvancedmathematics,

the radiationpattern of dipole can bedrawed.




1个 dipole(received power)：1mW

Multiple dipole matrixReceived power：4 mW

GAIN= 10log(4mW/1mW) = 6dBd

HalfwaveDipole Radiation Pattern




Antenna Work Frequency Range

• CDMA(CELLULA） 800 MHz: 824-894MHz• CDMA(PCS) 1900 MHz: 1850-1990MHz

Both transmitting and receiving antenna can only work

in a specific frequency range.

Antenna frequency range is defined：

The frequency bandwidth, in which the antenna gain

drop less than 3 dB and VSWR should be ≤ 1.5 .

Generally inside this band, the antenna performance indifferent frequency is a little different, but it’s

acceptable.

Both transmitting and receiving antenna can only work

in a specific frequency range.

Antenna frequency range is defined：The frequency bandwidth, in which the antenna gain

drop less than 3 dB and VSWR should be ≤ 1.5 .

Generally inside this band, the antenna performance indifferent frequency is a little different, but it’s

acceptable.




Work Frequency Range（ BANDWIDTH ）= 896 - 824 = 72MHz

（Decided by antenna manufacturer and Test)

Work Frequency Range（ BANDWIDTH ）= 896 - 824 = 72MHz（Decided by antenna manufacturer and Test)

Optimum 1/2 wavelength

for dipole at 860MHz

at

896

MHz

Antenna

Dipole

at

824

MHz

Antenna Work Frequency Range




Antenna Radiation Pattern

The first basic function of antenna is to radiateenergy to outer space.

The second basic function is to radiate most of

energy to the desired direction.

But in fact, the practical radiation is very

complex, it is called: “radiation pattern”

The first basic function of antenna is to radiate

energy to outer space.

The second basic function is to radiate most of

energy to the desired direction.

But in fact, the practical radiation is verycomplex, it is called: “radiation pattern”




Antenna Gain

Attention: Antennas are passive devices; they doNOT amplify RF energy

Attention: Antennas are passive devices; they doNOT amplify RF energy

What is gain：

On the condition of same input power and same

position of space , the ratio between the power

radiated from the practical antenna and from ideal

isotropic antenna.

What is gain：

On the condition of same input power and same

position of space , the ratio between the power

radiated from the practical antenna and from ideal

isotropic antenna.Same amount of

energy, focussed in a

particular direction




Halfwave dipole

Ideal Isotropic antenna

eg: 0dBd = 2.15dBi

Gain’s Calculation: dBd and dBi

2.15dB




Gain’s Calculation: dBd and dBi

• Isotropic vs. dipole

PLAN VIEW

isotropic

dipole

dB Gain

ref Dipole (dBD)

dB Gain

ref isotropic (dBi)

0dBi

(ref)

0dBD(ref)

Directional

Antenna

Azimuth Pattern

G（θ、φ）=s1（θ、φ）/s0 unit：dBi

G’ （θ、φ）== s1（θ、φ）/ GA0 unit:dBd




ERP and EIRP

• Effective Radiated Power (ERP and EIRP)

– apparentpower in a particular direction. It isequal to actual transmitter power timesantenna gain in that direction.

– Radiated power = Input power xantenna gain

or in dB’ = dBm + dB(i or d)

eg: 50dBm + 4.4 dBi

EIRP = 54.4 dBm (right picture)

• ERP is expressed in comparison to a standardradiator

– ERP: compared with dipole antenna

– EIRP: compared with isotropic antenna

AB

EIRP B A (ref)

100w275w

ReferenceAntenna

TX100 W

A

DirectionalAntenna

TX100 W

B




Antenna Gain Example

BaseStation

Transmitter

(20 watts)

Convert to dBm

10Log(20) + 30 = +43 dBm

jumper

Heliax

Cable

jumper

-0.5dB

-0.5dB

-3dB

Antenna Gain

= + 18 dBi

Ant Input

Power = + 39dBm

EiRP = +39 + 18 = +57 dBm




Beamwidth

60° (eg) Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

In the radiation pattern there are several lobes, the

strongest is main lobe, the others are side lobe.

Beside the peak of main lobe，the radiation will become

weaker and weaker. The angel between two positionwhich is 3 dB below, is called :beamwidth or halfpower

angel 。

The narrower of beamwidth, the better of concentration

radiation and the higher of the gain。

In the radiation pattern there are several lobes, the

strongest is main lobe, the others are side lobe.

Beside the peak of main lobe，the radiation will become

weaker and weaker. The angel between two positionwhich is 3 dB below, is called :beamwidth or halfpower

angel 。

The narrower of beamwidth, the better of concentration

radiation and the higher of the gain。




Horizontal 3dB Beamwidth

Directional Antenna：65°/90°/105°/120° Omni：360°Directional Antenna：

65°

/90°

/105°

/120°

Omni：

360°




20°、30° beamwidth antennas only be used in narrow area or

highway；65°s are usually used in city area，90°s are more

used in suburb and courtyside.

20°、30° beamwidth antennas only be used in narrow area or

highway；65°s are usually used in city area，90°s are more

used in suburb and courtyside.

Horizontal 3dB Beamwidth

Typical 90°3dBbeamwidth

sketch map

Typical 90°3dBbeamwidth

sketch map




Vertical 3dB Beamwidth

Directional ： Omni：

48°,33°,15°,8°，are some familiar degrees to

define the vertical 3dB beamwidth。

If vertical beamwidth is small, then we can control

The coverage precisly by adjusting the downtilt.

48°,33°,15°,8°，are some familiar degrees todefine the vertical 3dB beamwidth。

If vertical beamwidth is small, then we can control

The coverage precisly by adjusting the downtilt.

AntennaDo ntilt




Antenna Downtilt

Mechanical Downtilt（0̊ ---10̊ )Physically tilt the antenna. The pattern in

front goes down, and behind goes uppopular for sectorizationand specialomni applications

Electrical Downtilt

(fixed and ajustable)Incremental phase shift is applied in thefeed networkthe pattern“droops”all around, like an

inverted saucercommon technique when downtiltingomni cells




Non down tilt Electronic downtilt Mechanical

downtilt

Different DowntiltsEffect




Downtilt Adjustment

In general, the original downtilt can be calculated：

θ=arctg(h/R)＋A/2

θ—antenna downtilth—antenna height

R—cell coverage radius

A---antenna vertical 3dB beamwidth

In this formula, the main lobe of antenna will point to the

edge of cell coverage .Actually ,the downtilt often need adjustment during

Optimization to ensure the real coverage not too far or Too near.

In this formula, the main lobe of antenna will point to the

edge of cell coverage .Actually ,the downtilt often need adjustment during

Optimization to ensure the real coverage not too far or Too near.




Front to Back Ratio

•Front-to-back ratio

—Antenna front-to-back ratio are measures of how much energy isradiated outside the antenna’s main beam.

F/B = 10 log(FP/BP) typically ：18---30dB , the larger the better

Back power Front power

Back Power(interference)

Front Power




DOWN SIDELOBE(dB)

UP SIDELOBE (dB)

Up and Down SidelobesRestraint

Usually ,the up sidelodeenergy is no useful, so upsideloberestraint: the

higher the better

SidelobeSuppression




ppand Null Filling

d




Antenna Input Impedance

Cable

50 ohms

Antenna

50 ohms

• When antenna and cable are connected, the best status is theycompletely match each other. That is: their impedance arecompletely same.

• Usually 4 parameters are used to scale the matching, they are “Reflectance; TravellingWave Coefficient; VSWR; ReturnLoss”.

• In everyday work, we more like to use VSWR and Return Loss.

• When antenna and cable are connected, the best status is theycompletely match each other. That is: their impedance arecompletely same.

• Usually 4 parameters are used to scale the matching, they are “Reflectance; TravellingWave Coefficient; VSWR; ReturnLoss”.

• In everyday work, we more like to use VSWR and Return Loss.

VSWR V l S di W R i




9.5 W50

ohms50 ohms

Forwarda: 10W

Backward: 0.5W

Return Loss： 10log(10/0.5) = 13dB

VSWR (Voltage Standing Wave Ratio)

VSWR -Voltage Standing Wave Ratio

VSWR Characteristics




VSWR Characteristics

• Impedance and Voltage Standing Wave Ratio (VSWR)Return Loss

– Input impedance of the antenna must match the characteristicimpedance of the transmission line

– Otherwise, a reflected wave is generated, directed backtowards the energy source.

– The ratio between the maximum and minimum voltage is

defined as the Voltage Standing Wave Ratio (VSWR).

Ant VSWR = 1.5:1Return Loss = 20 Log VSWR +1 = 14dB

VSWR-1+40 dBm

(10 watts)

+26 dBm

0dBi EIRP = +39.8 dBm

(400mW)

AntennaPolarization




Vertical Horizontal

+ 45degree slant - 45degreeslant

Antenna Polarization

• Polarization

– Polarization describes the orientation of the electric fieldvector.

• Polarization

– Polarization describes the orientation of the electric fieldvector.

Dual Polarization Antenna




V/H (Vertical/Horizontal) Slant (+/- 45°)


Polarization Discrimination




Polarization Discrimination

Power Transfer Between Antenna A

and Antenna B

A B

A

B

Co-Polarized

Cross-Polarized

Polarization

DiscriminationFree-Space

Environment

Severe MultipathEnvironment

Maximum energy transfer between Txand Rx antennas takes placewhen the antennas have the samepolarization and spatial orientation.

Maximum energy transfer between Txand Rx antennas takes placewhen the antennas have the samepolarization and spatial orientation.

Diversity Techniquesin Antenn




Diversity Techniques in Antenn

• Space diversity and polarization diversity

Signal received

by Antenna 1or Polarization1

Signal received

by Antenna 2 or Polarization2

Improved Combined Signal

Typical AntennaConfigurations




Typical Antenna Configurations

Typical Space DiversitySeparation

10--20λ

RX RX

Duplexer

TX

Duplex Antenna System Configuration

In engineering: d≥ 10~20λ. The diversity distance of the 1900M carrier should be more than 1.5m

while that of the 800M carrier should be more than 3.5m.

In engineering: d≥ 10~20λ. The diversity distance of the 1900M carrier should be more than 1.5m

while that of the 800M carrier should be more than 3.5m.





1000mW ( 1W)1mW

10log(1000mW/1mW) =30dB

Port IsolationIn dual polarization antenna, complete port isolation is impossible.

If one port is input energy, some interference must be found in another port.

In this example, the isolation is 30dB, the higher the better.

In dual polarization antenna, complete port isolation is impossible.

If one port is input energy, some interference must be found in another port.

In this example, the isolation is 30dB, the higher the better.

Antenna Mechanical Properties




Antenna Mechanical Properties

Antenna Dimensions




Antenna Dimensions

L×W×HLength：connected with vertical bandwidth and gainWidth：connected with horizontal bandwidthHeight：connected with techniques adopted

Antenna Weight




Antenna Weight

Affecting transmission and deploy

RadomeMaterial




Radome Material

PVC, FiberglassAnti-temperature、water-proof ，anti-aging，weatherresistant

AppearanceColor




Appearance Color

Good-looking, environment-protecting

Protected Antenna




Protected Antenna

Protected Antenna




Protected Antenna

Physical Parameters




Operating Temperature Range

Typical range：-40°C — +70°C

Physical Parameters

Storage Temperature Range

Typically：-40°C — +70°C

Connector Type

7/16”DIN，N，SMA

female




Mast

Mast diameter 45-90mm




Lightening Protection

Direct Ground




MAIN FEEDER




J UMP CABLE

Connectors




7/16”DIN-F CONNECTOR

7/16”DIN-M and N-M CONNECTOR

Feeder Installation Annex




Trimming Tool or Hand Tool K itClampEarthingKitWall GlandsUniversal Ground Bar

Main Content




BTS Antenna SystemStructure

BTS Antenna Specificationand Meanings

¾Antenna Types and Trends





Wide Band

Multiple Functions

Intelligent

Wide Band

Multiple Functions

Intelligent

“Intelligent” antennas…Introduction




Introduction

– Two types: switched beam and adaptive.– By combining signals in various phase

relationships, any pattern of nulls or

reinforcements can be created.– On the transmit side, energy is focused in a tight,

specific direction to avoid interference to others.

– On the receive side, a tight beam is formed that issensitive to signals coming from one direction,but not from others.

– The switched beam method combines signals in afixed number of ways in order to find the best fitat a particular moment.

– Adaptive antennas synthesize beam patternsrather than choose from predetermined patterns.

Intelligent antennas




Example calculation – beam tracing




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24 CDMA Antenna System

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