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CDMAAntenna Introduction

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Syllabus BTS Antenna System

Introduction 

Antenna Diversity

Electrical properties

Mechanical properties

Antenna Development

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BTS Antenna System Introduction

antenna 

7/16 Tie-in 

1/2“ 

cable 

7/8“  cable1/2 cable 

BTS 

arrester 

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Syllabus BTS Antenna System

Introduction

Antenna Diversity

Electrical properties

Mechanical properties

Antenna Development

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Antenna Diversity

Space Diversity

Space Diversity：when there exist certain space between two

receiving antennas,they can receive the same signal with

different fading envelope . and if the correlation coefficient is

less than 0.7, the diversity receiving requirement is met. 

Space Diversity requires ： D>10λ h/D≤11 

Where H : the height of the antenna.D : the distance between two antennas

Space Diversity is only used in horizontal

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Polarization Diversity

Polarization Diversity can beobtained if dual polarization (+

45°/- 45°) antenna is used at each

sector of each carrier

Antenna Diversity

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Syllabus BTS Antenna System

Introduction

Antenna Diversity

Electrical properties

Mechanical properties

Antenna Development

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Electrical properties

Blah blahblah bl ah

Frequency Range

Impedance

Dipoles Polarization

Gain

VSWR Beamwidth

Downtilt

PatternElevation Upper Side lobes & Null Fill

Third Order Intermodulation

Front to Back Ratio Isolation

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Wavelength 

1/2 Wavelength 

1/4 Wavelength

1/4 Wavelength

1/2 Wavelength

Dipole

1800MHz ：166mm

900MHz ：333mm

Dipoles

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One dipole Received Power ：1mW multiple dipoles Received Power ：4 mW

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

Dipoles

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10log(8mW/1mW) = 9dBd

Sector antenna

Received Power ：8mW

Omnidirectional array

Received Power ：4mW

(down look)

Antenna

Dipoles

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Frequency Range

For CDMA1900 system， the frequency

range of antenna can be 1850－1990MHZ

For CDMA800 system,the frequency range

of antenna can be 824－896MHZ

For GSM900 system，the Frequency

Range of antenna can be 890-960MHz、

870-960MHz、807-960 MHz or 890-1880MHz.

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BANDWIDTH = 896 - 824 = 72MHz

Optimum 1/2 wavelength

for dipole at 860MHz

at896

MHz

Antenna

Dipole

at824

MHz

The Frequency Range of antenna in

CDMA800M system

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Impedance

50

Cable

50 ohms

Antenna

50 ohms

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9.5 W80

ohms50 ohms

forward: 10W

reverse: 0.5W

Return Loss：10log(10/0.5) = 13dB

VSWR (Voltage Standing Wave Ratio)

VSWR 

576.12236.01

2236.01

1

1VSWR 

10

5.0

＝＝

Usual Request：VSWR 1.5

Reflection Coefficient：=(VSWR-1)/(VSWR+1)

Return Loss：RL=-20lg  

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Polarization

Vertical Horizontal

+ 45degree slant - 45degree slant

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

Polarization

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Linear,vertical

Polarization

dual linear 45 slant

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Gain

Ratio of antenna power density at a

distant point relative to that of an

isotropic radiator as the two input powervalues are the same.

Unless otherwise specified, the gainusually refers to the direction of 

maximum radiation.

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Antenna gain is usually expressed in dBi or dBd

dBi

Gain relative to an isotropic antenna when the

reference antenna is an isotropic antenna.

dBd

Gain relative to a half-wave dipole when the

reference antenna is a half-wave dipole.

Gain

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half-wave dipole 

isotropic radiator 

eg: 0dBd = 2.15dBi

2.15dB

Gain

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Pattern

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120° (eg) Peak

Peak - 10dB

Peak - 10dB

10dB Beamwidth

60° (eg) Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

Beamwidth

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3dB Beam width Horizontal

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

Omni Antenna：360° 

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3dB Beam width VerticalDirectional Antenna Omni Antenna

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Down Tilt

Mechanical Downtilt

Settled Electrical Downtilt

Modified Electrical Downtilt

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Down Tilt

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Down Tilt 

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No Downtilt Electrical DowntiltMechanical

Downtilt

Down Tilt

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Down Tilt 

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Front to Back Ratio

The ratio of front max beam to

back max beam

F/B = 10 log typically： 25dB(Front Power)

(Back Power)

Back Power Front Power 

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Elevation Upper Side lobes & Null Fill

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Elevation Upper Side

lobes(dB)

Sidelobes

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Null Fill

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Permitted Power

The permitted power range

of common antenna

25-1500 W

The permitted power of 

BTS antenna should bebigger than 200 W

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Third Order Inter modulation 

IMD@243dBmf 1, f 2, 2f 1-f 2, 2f 2-f 1 

830MHz,835MHz,840MHz,845MHz

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1000mW ( 1W) 1mW

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

Isolation

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Syllabus BTS Antenna System

Introduction

Antenna Diversity

Electrical properties

Mechanical properties

Antenna Development

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Mechanical properties

Weight

Radome Material

Operation and Storage

Configuration Parameters

Mast

Light Protection

Dimensions

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Dimensions

lengthwidthheight

length ：be related to vertical

beamwidth and gainwidth ： be related to horizontal

beamwidth

height ： be related to thetechnology of antenna

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Weight

Having an Influence on

Transportation and Construction

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Radome Material

PVC, ABS, fiberglass,etc

Sun-proof 、prevent frostbite，Fire-

retardant etc

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Operation and Storage

Storage Temperature Range： 

Operating Temperature Range： 

Typical：-40°C  —  +70°C

Typical：

-40°

C — 

+70°

C

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Configuration Parameters

Flat Plate Area

Shipping Dimensions

Wind Load

lengthwidthheight

Eg: 83N at 160 km/h

The smaller the better

Connector Type

7/16”DIN，N，

SMA female

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Mast

Mast diameter 45-90mm

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Light Protection

DC Ground

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Syllabus

BTS Antenna System

Introduction

Antenna Diversity

Electrical properties

Mechanical properties

Antenna Development

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Antenna Development

Wide Frequency

Much Function

High Integration

Smart Antenna

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