Antennas for CDMA System

第 2 页

Contents

Base station antenna specification and meanings

Antenna types and trends

第 3 页

Technical Data

B lah

blahb la h bl ah

第 4 页

Electrical properties Operation 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

Mechanical properties Size Weight Robe material Appearance and color Working temperature Storage termperature Windload Connector types Package Size Lightening

Electrical properties

第 6 页

Wavelength

1/2 Wavelength

1/4 Wavelength

1/4 Wavelength

1/2 Wavelength

Dipole

Dipoles

1900MHz ： 157mm

800MHz ： 375mm

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1 个 dipole (received power) ： 1mW

Multiple dipole matrixReceived power ： 4 mW

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

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

“Sector antenna”Received power ： 8mW

Omnidirectional array”Received power ： 1mW

(Overlook

Antenna

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Frequency Range

CDMA(CELLULA ） 800 MHz: 824-894MHz

CDMA(PCS/PCN) 1900 MHz: 1850-1990MHz

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Impedance

50

Cable

50 ohms

Antenna 50 ohms

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9.5 W80

ohms50 ohms

Forwarda: 10W

Backward: 0.5W

Return Loss ： 10log(10/0.5) = 13dB

VSWR (Voltage Standing Wave Ratio)

VSWR

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1.5=(VSWR-1)/(VSWR+1)RL=-20lg

第 13 页

Polarization

Vertical Horizontal

+ 45degree slant - 45degree slant

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

第 15 页

Linear,verticaldual linear 45 slant

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Dipole

Ideal radiating dot source(lossless radiator)

eg: 0dBd = 2.15dBi

dBd and dBi

2.15dB

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Pattern

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Beamwidth

120° (eg) Peak

Peak - 10dB

Peak - 10dB

10dB Beamwidth

60° (eg) Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

第 20 页

3dB Beam width Horizontal

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

第 21 页

3dB Beam width Vertical

Directional ： Omni-directional ：

第 22 页

Down Tilt

Mechanical down tiltFixed electronic down tiltAdjustable electronic down tilt

第 23 页

Demonstration of Electronic Down-tilt

第 24 页

Non down tilt Electronic downtilt Mechanical downtilt

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Front to Back Ratio

Ratio of maximum mainlobe to maximum sidelobe

F/B = 10 log(FP/BP) typically ： 25dB

Back power Front power

第 26 页

Upper Side lobes Suppression & Null Fill

第 27 页

Sidelobes

DOWN SIDELOBE (dB)

UP SIDELOBE (dB)

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Permitted Power

Continuous :25-1500watts

peak :n2p

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1000mW ( 1W) 1mW

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

Isolation

Mechanical properties

第 33 页

Dimensions

LWHLength ： connected with vertical bandwidth and

gainWidth ： connected with horizontal bandwidthHeight ： connected with techniques adopted

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Weight

Affecting transmission and deploy

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Radome Material

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

aging ， weather resistant

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ColourGood-looking,

environment-protecting

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第 38 页

Operating Temperature Range

Typical range ： -40°C — +70°C

第 39 页

Storage Temperature Range

Typically ： -40°C — +70°C

第 40 页

Wind Load

Eg: 83N at 160 km/h

第 41 页

Connector Type

7/16”DIN ， N ， SMA female

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Mast

Mast diameter 45-90mm

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Lightening Protection

Direct Ground

第 44 页

Antenna Systems

Antenna systems include more than just antennas Transmission Lines

necessary to connect transmitting and receiving equipment Other Components necessary to achieve desired system function

Filters, Combiners, Duplexers - to achieve desired connections Directional Couplers, wattmeters - for measurement of performance

Manufacturer 抯 system may include some or all of these items remaining items are added individually as needed by system operator

F R

Duplexer

Comb-iner

BPF

TX

RX

TXTransmission LineJumper

Jumpers

DirectionalCoupler

Antenna

第 45 页

Characteristics of Transmission Lines

FoamDielectric

AirDielectric

Typical Coaxial CablesUsed as Feeders in Wireless Applications

Physical CharacteristicsType of Line

coaxial, stripline, open-wirebalanced, unbalanced

Physical ConfigurationDielectric:

airfoam

Outside Surface:unjacketedjacketed

special: plenum rated

Size (nominal outer diameter)1/4?1/2? 7/8? 1-1/4? 1-7/8? 2-

1/4? 3

第 46 页

Characteristics of Transmission Lines

Electrical Characteristics Attenuation:

varies with frequency, size, dielectric characteristics of insulation

usually specified in db/100 ft and/or db/100 m

Characteristic Impedance ZO (50 ohms is the usual commercial standard; 75 sometimes used) value set by inner/outer diameter ratio and d

ielectric characteristics of insulation connectors must preserve constant impedanc

e (see figure at right) Velocity Factor

determined by dielectric characteristics of insulation.

Power-Handling Capability varies with size, conductor materials, dielect

ric characteristics

dD

Characteristic Impedance of a Coaxial Line

Zo = ( 138 / ( 1/2 ) ) Log10 ( D / d )

= Dielectric Constant = 1 for vacuum or dry air

第 47 页

Transmission Lines:Special Electrical Properties

Transmission lines have impedance-transforming properties When terminated with same impeda

nce as Zo, input to line appears as impedance Zo

When terminated with impedance different from Zo, input to line is a complex function of frequency and line length. Use Smith Chart or formulae to compute

Special case of interest: Line section one-quarter wavelength long has convenient properties useful in matching networks ZIN = (Zo

2)/(ZLOAD)

Zo=50ZLOAD=

50ZIN = 50

Matched Condition

Zo=50ZLOAD=

83-j22

ZIN = ?

Mis-Matched Condition

Zo=50ZLOAD=

100ZIN=25

/4

ZIN= ZO2

/ ZLOAD

Deliberate Mis-Matchfor Impedance Transformation

第 48 页

Transmission Lines:Some Practical Considerations

Transmission Lines: Some Practical Considerations Periodicity of inner conductor supportin

g structure can cause VSWR peaks at some frequencies, so specify the frequency band when ordering

Air dielectric lines: lower loss than foam-dielectric; dr

y air is excellent insulator shipped pressurized; do not accept

delivery if pressure leak Foam dielectric lines

simple, low maintenance; despite slightly higher loss

small pinholes and leaks can allow water penetration and gradual attenuation increases Foam

Dielectric

AirDielectric

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MAIN FEEDER

第 50 页

JUMP CABLE

第 51 页

7DIN CONNECTOR

DIN & N CONNECTOR

第 52 页

Lightening Arrestor

Rf port 2

Grounding

第 53 页

ACCESSORIESTrimming Tool or Hand Tool KitClampEarthing KitWall GlandsHoisting StockingUniversal Ground Bar

第 54 页

Antenna

7/16 Din Connector

7/8“ Cable

Grounding

1/2“ Jumper

Cabinet

EMPGrounding clip

Grounding bar

1/2 Clamp

Tower Top Amplifier

7/8“ Cable

Machine house

1/2 Jumper

第 55 页

Transmission Lines:Important Installation Practices

Respect specified minimum bending radius! Inner conductor must remain

concentric, otherwise Zo changes

Dents, kinks in outer conductor change Zo

Don 抰 bend large, stiff lines (1-5/8?or larger) to make direct connection with antennas. Use appropriate jumpers, weatherproofed properly. Secure jumpers against wind vibration.

ObserveMinimumBendingRadius!

第 56 页

Transmission Lines:Important Installation Practices

During hoisting, allow line to support its own weight only for distances approved by manufacturer. Deformation and stretching may result, changing the Zo. Use hoisting grips, messenger cable

After mounting, support the line with proper mounting clamps at manufacturer 抯 recommended spacing intervals. Otherwise, strong winds will set up damaging metal-fatigue-inducing vibrations

200 ft~60 MMax. 3-6 ft

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RF Filters: Types and Applications

Filters are the basic building blocks of duplexers and more complex devices

Most manufacturers network equipment includes internal bandpass filters at receiver input and transmitter output

Filters are also available for special applications

number of poles (filter elements) and other design variables determine filter抯 electrical characteristics bandwidth, rejection, insertion lo

ss, slopes, losses, ripple, etc.

Notice construction: RF input excites one quarter-wave element and electromagnet fields propagate from element to element, finally exciting the last element which is directly coupled to the output.

Each element is individually set and forms a pole in the filter 抯 overall response curve.

Typical RF Bandass Filter

/4

第 58 页

RF Filters: Basic Characteristics & Specifications

Types of Filters Single-Pole:

Pass Reject (notch)

Multi-pole: Band-Pass Band-Reject

Key Electrical Characteristics insertion loss passband ripple passband width

upper, lower cutof f frequencies attenuation slope at band edge ultimate out-of-band attenuation

Typical bandpass filters have insertion loss of 1-3 dB. and passband ripple of 2-6 dB.

Bandwidth is typically 1-20% of center frequency, depending on application. Attenuation slope and out-of-band attenuation depend on # of poles & design

Typical RF Bandass Filter

0

Att

enu

atio

n,

dB

Frequency, MegaHertz

passband rippleinsertion loss

-3 dB passbandwidth

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Typical Tuned Combiner Application

Basics of Transmitting Combiners

Purpose: Allow multiple transmitters to feed single antenna, and provide: minimum loss from transmitter to antenn

a maximum isolation between transmitters

Types: Tuned

low insertion loss ~1-3 dB transmitter frequencies must be signi

ficantly separated Hybrid

insertion loss -3 dB per stage no restriction on transmitter frequen

cies Linear Amplifier

linearity and intermodulation are major design & operation issues

TX TX TX TX TX TX TX TX

Antenna

Typical Hybrid Combiner Application

TX TX TX TX TX TX TX TX

Antenna

~-3 db

~-3 db

~-3 db

第 60 页

Combiners: CDMA Considerations

CDMA operators will want to combine multiple CDMA carriers into single antennas; combiners will be needed

Tuned Combiner Technique must use multi-pole bandpass filters adjacent-frequency CDMA carriers prob

ably cannot be combined using this technique alone

Hybrid Technique substantial insertion loss will limit numb

er of carriers per antenna to perhaps 4 if technique used alone

Composite method using staggered tuned combiners and hybrid combiners, and/or

Linear amplifiers will probably be exploited for high-density CDMA BTS configurations in the future

Composite Method:Tuned & Hybrid

f4 f6f5f1 f7f3 f8f2

Hybrid Combiner

One Operator 抯 CDMA Carriers

Antenna

Linear Amplifier Method

f4 f6f5f1 f7f3 f8f2

Linear Amplifier

One Operator 抯 CDMA Carriers

Antenna

第 61 页

Duplexer Basics

Duplexer Purpose: allow simultaneous transmitting and receiving on one antenna Zte 1900 MHz BTS RFFEs include i

nternal duplexer Zte 800 MHz. BTS does not include

duplexer but commercial units can be used if desired

Important Duplexer Specifications TX pass-through insertion loss RX pass-through insertion loss TX-to-RX isolation at TX freq. (RX

intermodulation issue) TX-to-RX isolation at RX freq. (TX

noise floor issue) internally-generated intermod limit s

pecification

fR fT

RX TX

Antenna

Duplexer

Principle of Operation

Duplexer is composed of individualbandpass filters to isolate TX fromRX while allowing access to antennafor both. Filter design determinesactual isolation between TX and RX,and insertion loss TX-to-Antenna and RX-to-Antenna.

第 62 页

Directional Couplers

This device measures forward and reflected energy in a transmission line. It has 4 ports: Input (from TX), Output (to load) Forward, Reverse Samples

Sensing loops probe E& I in line equal sensistivity to E & H fields terminations absorb induced curren

t in one direction, leaving only sample of other direction

Typical Performance Specs: Coupling factor ~20, ~30, ~40 db.,

order as appropriate for application Directivity ~30-~40 dB., f($)

defined as relative attenuation of unwanted direction in each sample

Principle of Operation

ZLOAD= 50

Input

Reverse Sample

Forward Sample

RT

RT

Typical Directional Coupler

Main line E & I induce equal signals in sense loops. E is direction-independent, but the polarity depends on direction andcancels sample induced in one direction.Thus sense loop signals are directional.One end is used, the other terminated.

第 63 页

Return Loss and VSWR Measurement

A perfect antenna will absorb and radiate all the power fed to it. Real antennas absorb most of the power, but reflect a portion back down t

he line. A Directional Coupler or Directional Wattmeter can be used to measure t

he magnitude of the energy in both forward and reflected directions. Antenna specs give maximum reflection over a specific frequency range. Reflection magnitude can be expressed in the forms VSWR, Return Loss,

or reflection coefficient. VSWR = Voltage Standing Wave Ratio

Transmission Line

AntennaDirectionalCoupler Fwd

Refl

RFPower

第 64 页

Return Loss and VSWR Calculations

Forward Power, Reflected Power, Return Loss, and VSWR are related by the following equations and the graph. Typical antenna VSWR specifi

cations are 1.5:1 maximum over a specified band.

VSWR 1.5 : 1

= 14 db return loss

= 4.0% reflected power

VSWR vs. Return Loss

VSWR

0

10

20

30

40

50

1 1.5 2 2.5 3

VSWR =

Reflected PowerForward Power

Reflected PowerForward Power

1 +

1 -Reflected PowerForward Power

ReturnLoss, dB = 10 x Log10 ( )

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Thank you