GSM Antenna System

8/15/2019 GSM Antenna System

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Antenna System

ZTE University



Objective

By the end of this course, you will be able:

To Understand the concept of dipole

To state GSM antenna specifications

To comprehend the principle of antenna selection



Content

Antenna overview

Antenna specifications

Principle of antenna selection



Blah blah

blah bl ah

Radio Waves

A form of electromagnetic radiation typically

generated as disturbances sent out by

oscillating charges on a transmitting antenna



Definition

An Antenna is any

device used tocollect or radiate

Electromagnetic

Waves



Linear antennas are

used:

Monopole (Slab)

Dipole Elements

Mobile Phones

Base Tranceiver

Station Antenna

• Single Monopole

• Patch Antenna

• Array of dipoles

Antenna for mobile communication



Antenna basic structure

Antenna are generally

composed of stacked of dipole

bundling their radiated powerto form a desired antenna

pattern in vertical plains

around the antenna

Depending on the gain desired

that wants to be achievedseveral of those diploes can

be arranged on top of one

another



DIPOLES

Wavelength

1/2 Wavelength

1/4 Wavelength

1/4 Wavelength

1/2 Wavelength

Dipole

1800MHz ：166mm

900MHz ：333mm

Generation of radio waves



1个 dipoleReceived Power ：1mW

Multiple dipole matrixReceived Power ：4 mW

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

Half wave dipole



Gain=10log(8mW/1mW) = 9dBi

“ Omnidirectional array”

Received power ：1mW

(Overlook

Antenna

“Sector antenna”

Received power ：8mW

Isotropic antenna



Dipole

Ideal radiating dot source

(lossless radiator)

0dBd = 2.15dBi

2.15dB

dBd and dBi



dBd and dBi



Content

Antenna overview





Antenna electrical properties

Operating Frequency Band

Input impedance

VSWR

Polarization

Gain

Radiation Pattern

Horizontal/Vertical beamwidth Downtilt

Front/back ratio

Sidelobe suppression and null filling Power capability

3rd order Intermodulation

Insulation



Type Frequency Range

GSM 900 890 - 960 MHz

GSM 1800 1710 - 1880 MHz

890 - 960 MHz

1710 - 1880 MHzGSM Dual Band

GSM antenna frequency range



BANDWIDTH = 960 - 890 = 70MHz

Optimum 1/2 wavelength

for dipole at 925MHz

at

960

MHz

AntennaDipole

at

890

MHz

GSM antenna frequency range



Standard Value: 50Ω

Cable

50 ohms

Antenna

50 ohms

Impedance



9.5 W80

ohms50 ohms

Forward: 10W

Backward: 0.5W

Return Loss：

10log(10/0.5) = 13dB

VSWR (Voltage Standing Wave Ratio)

Voltage standing wave ratio (VSWR)



VSWR 1.5 Γ = (VSWR-1)/(VSWR+1)

RetureLossRetureLoss = -20lg Γ

Calculation of VSWR



120

(eg) Peak

Peak - 10dB

Peak - 10dB

10dB Beamwidth

60

(eg) Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

Bandwidth



Directional Antenna

65

/90

/105

/120

Omni 360

Omni-directional Directional

3dBm horizontal beamwidth




3dBm vertical beamwidth




Antenna structure types



Vertical Horizontal

+ 45degree slant - 45degree slant

Polarization



Space diversity



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

Polarization diversity



Linear Polarization,vertical

X Polarization, ±45 °

Types of antenna



Antenna down tilt

Mechanical down tilt

Fixed electronic down tilt Adjustable electronic down tilt



Mechanical down tile

It is achieved by physically

tilting the antenna out of theperpendicular by using down

tilt kit

PROS: Cost efficient and

flexible

CON: Has no effect on theside-lobe characteristics of the

antenna



Input Signal

Electrical down tilt

Electrical downtilt can be fixed or adjustable

Fixed is tuned by the manufacturer

Adjustable allows adjustment in a certain level on the rear of the

antenna



Non down tilt Electronic downtilt Mechanical

downtilt

Down tilt



Antenna tilt development



F/B = 10 log(FP/BP) typically ： 25dB

Back power Front power

FRONT-TO-BACK Ratio

Ratio of maximum mainlobe to maximum

sidelobe



Upper sidelobe suppression and null fill



Upper sidelobe suppression and null fill



913 MHz 936 MHz 959 MHz 982 MHz

IMD@2×

43dBmf1, f2, 2f1-f2, 2f2-f1

Intermodulation

It occurs when two signals of a different frequency mix in anon-linear device

It can be a problem at any site that has two or more

transmitters It can be caused by a transmitter of the same system or by a

transmitter in another site that is co-sited or has a site in the

neighborhood



1000mW ( 1W) 1mW

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

Isolation



Antenna mechanical properties

Size

Weight

Radome material Appearance and color

Working temperature

Storage temperature

Windload

Connector types Package Size

Lightning Protection



Dimension

L×W×H

Length：connected with vertical bandwidth and gain

Width：connected with horizontal bandwidth Height：connected with techniques adopted



Weight

A factor that can affect transport and

deployment



PVC, Fiberglass

Anti-temperature, water-proof ， anti-

aging，weather resistant

Radome materials



Good-looking

Environment-protecting

Color



Temperature range

Operation and storage

Typical range：-40°C — +70°C



Connector type

7/16”DIN，N，SMA

Female/male



Mast diameter 45-90mm

Mast



Direct Ground

Lightning protection



Antenna types

By frequency band: GSM900, GSM1800,

GSM900/1800

By polarization: Vertical, Horizontal,±45º linearpolarization, circle polarization

By pattern: Omni-directional, directional

By down-tilt: Non, mechanical, electronic

adjustment, remote control

By function: Transmission, receiver,transceiver



7/8” Main feeder

Feeder cable



1/2” JUMPER CABLE）

Jumper cable



7/16” DIN-F DIN CONNECTOR）

7/16” DIN-M DIN & N CONNECTOR）

Connector



Rf port 2

Grounding

Lightning arrestor



Accessories

Trimming Tool or Hand Tool Kit

Clamp

Earthing Kit

Wall Glands

Hoisting Stocking Universal Ground Bar



Antenna

7/16 Din

Connector

7/8“ Cable

Grounding

1/2“ Jumper

Cabinet

EMP

Grounding clip

Grounding bar

1/2 Clamp

Tower Top

Amplifier

7/8“ Cable

Machine house

1/2 Jumper

Antenna system



Content

Antenna overview





Radio propagation in cities

Environment features: Densely deployed BTS，small coverage area

Decrease over coverage and interference, increase

frequency reuse factor





Radio propagation in suburb/rural area

Environment features:

Loosely deployed BTS

light traffic large coverage



Antenna selection in suburb/rural area

Polarization Both dual-polarized and vertical

Direction directional

3dB bandwidth 90°105°

Gain16-18dBi directional

or 9－11dBi omni

Tilt down angle Mechanical tilt down; 50m high; null fill



Radio propagation in road/highway environment


Low traffic

Fast movingsubscribers

Focus on coverage.

Strip coverage

Two sectors

Omni-cell when pass

towns or tourist site



Antenna selection for highway


Direction Narrow beamwidth directional

3dBbandwidth

30°

Gain 18dBi－22dBi

Tilt down

angleNo tilt down



Radio propagation in mountainous environment


Block by mountains

Big propagation loss Difficult to cover



Antenna selection in mountainous area


Direction Omni or directional

3dB bandwidth Big 3db verticle bandwidth

GainOmni (9-11dBi）

Directional (15-18dBi）

Tilt down angle Null fill & electrical tilt down



Documents

GSM Antenna System