bsa antenna theory_mod

PRIVATE AND CONFIDENTIAL

© CommScope 1

Basic Principles For Daily Applications

Antenna Theory

Base Station Antenna SystemsMarch 2009


© CommScope 2

Base Station Antenna Technology Evolution

Omni Directional

Vertical Polarization

DualPol®MIMO

DualPol® RET

Interference ReductionMIMO

Dual BandCapacity Improvement

with FrequencyMIMO

DigitalBeam Former

SDMACapacity

SmartBeam® Capacity”Load Balance

MIMO

AntennaCoreTechnology

AMPS

GSM

CDMA

W-CDMA

WiMAX

TD-SCDMA

LTE

AirInterfaces Dominate Application Significant Application Low Application


© CommScope 3

F0 ¼

¼

Dipole

F0 (MHz) (Meters) (Inches)

30 10.0 393.6

80 3.75 147.6

160 1.87 73.8

280 1.07 42.2

460 0.65 25.7

800 0.38 14.8

960 0.31 12.3

1700 0.18 6.95

2000 0.15 5.9


© CommScope 4

Source: COMSEARCH

3D View Antenna Pattern


© CommScope 5

Understanding The Mysterious “dB”

dBd Signal strength relative to a dipole in empty space

dBi Signal strength relative to an isotropic radiator

dB Difference between two signal strengths

dBm Absolute signal strength relative to 1 milliwatt

1 mWatt = 0 dBm1 Watt = 30 dBm20 Watts = 43 dBm

dBc Signal strength relative to a signal of known strength, in this case: the carrier signal

Example: –150 dBc = 150 dB below carrier signalIf two carriers are 20 Watt each = 43 dBm–150 dBc = –107 dBm or ~0.02 pWatt or ~1 microvolt

Note: TheLogarithmic Scale10 * log10 (Power Ratio)


© CommScope 6

Effect Of VSWR

Good VSWR is only one component of an efficient antenna.

VSWRReturn

Loss (dB)Transmission

Loss (dB)Power

Reflected (%)Power

Trans. (%)

1.00 0.00 0.0 100.0

1.10 26.4 0.01 0.2 99.8

1.20 20.8 0.04 0.8 99.2

1.30 17.7 0.08 1.7 98.3

1.40 15.6 0.12 2.8 97.2

1.50 14.0 0.18 4.0 96.0

2.00 9.5 0.51 11.1 88.9


© CommScope 7

Shaping Antenna Patterns

Vertical arrangement of properly phased dipoles allows

control of radiation patterns at the horizon as well as

above and below the horizon. The more dipoles that are

stacked vertically, the flatter the vertical pattern is and the

higher the antenna coverage or ‘gain’ is in the general

direction of the horizon.


© CommScope 8

• Stacking 4 dipoles vertically in line changes the pattern shape (squashes the doughnut) and increases the gain over single dipole.

• The peak of the horizontal or vertical pattern measures the gain.

• The little lobes, illustrated in the lower section, are secondary minor lobes.

• General Stacking Rule• Collinear elements (in-line vertically).• Optimum spacing (for non-electrical tilt) is approximately 0.9λ.• Doubling the number of elements increases gain by 3 dB, and reduces vertical beamwidth by half.

Shaping Antenna Patterns (Continued)

Aperture of Dipoles

Vertical Pattern

Horizontal Pattern

4 Dipoles Vertically Stacked

Single Dipole


© CommScope 9

Gain

What is it?Antenna gain is a comparison of the power/field characteristics of a device under test (DUT) to a specified gain standard.

Why is it useful?Gain can be associated with coverage distance and/or obstacle penetration (buildings, foliage, etc).

How is it measured?It is measured using data collected from antenna range testing. The reference gain standard must always be specified.

What is Andrew standard?Andrew conforms to the industry standard of +/–1 dB accuracy.


© CommScope 10

• An isotropic antenna is a single point in space radiating in a perfect sphere (not physically possible).

• A dipole antenna is one radiating element (physically possible).

• A gain antenna is two or more radiating elements phased together.

Gain References (dBd And dBi)

0 (dBd) = 2.14 (dBi)

Isotropic Pattern

3 (dBd) = 5.14 (dBi)

Dipole Pattern

Isotropic (dBi)Dipole (dBd)Gain

dBd

dBi


© CommScope 11

Principles Of Antenna Gain

0 dBd

+3 dBd

+6 dBd

+9 dBd

-3 dB-3 dB

180°

90°

-3 dB-3 dB

45°

-3 dB-3 dB

Directional Antennas, Top ViewOmni Antenna, Side View

0 dBd 60°

-3 dB

-3 dB

+3 dBd 30°

-3 dB

+9 dBd7.5°

-3 dB

+6 dBd 15°-3 dB


© CommScope 12

# o

f R

adia

tors

Ver

tica

lly S

pac

ed (

0.9

)Theoretical Gain Of Antennas (dBd)

3 dB Horizontal Aperture(Influenced by Grounded Back “Plate”)

Typical Lengthof Antenna (ft.)

360° 180° 120° 105° 90° 60° 45° 33°800/900 MHz

PCSDCS

1800/1900Vertical

Beamwidth

1 0 3 4 5 6 8 9 10.5 1 0.5 60°

2 3 6 7 8 9 11 12 13.6 2 1 30°

3 4.5 7.5 8.5 9.5 10.5 12.5 13.5 15.1 3 1.5 20°

4 6 9 10 11 12 14 15 16.6 4 2 15°

6 7.5 10.5 11.5 12.5 13.5 15.5 16.5 18.1 6 3 10°

8 9 12 13 14 15 17 18 19.6 8 4 7.5°

Could be horizontal radiator pairs for narrow horizontal apertures.


© CommScope 13

• Gain (dBi) = Directivity (dBi) – Losses (dB)

• Losses: ConductorDielectricImpedancePolarization

• Measure using ‘Gain by Comparison’

Antenna Gain


© CommScope 14

• Vertical polarization

– Traditional land mobile use

– Omni antennas

– Requires spatial separation for diversity

– Still recommended in rural, low multipath environments

• Polarization diversity

– Slant 45° (+ and –) is now popular

– Requires only a single antenna for diversity

– Lower zoning impact

– Best performance in high and medium multipath environments

Measured data will be presented in the Systems Section

Antenna Polarization


© CommScope 15

Dipole

Elements

1800/1900/UMTSDirected Dipole™

Patch 800/900 MHzDirected Dipole™

MARMicrostrip Annular Ring

Various Radiator Designs

DualPol® (XPol)Directed Dipole™


© CommScope 16

Single Dipole Crossed Dipole

Dipoles


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Feed Harness Construction

Center Feed(Hybrid)

ASP705K

Series Feed

ASP705(Old Style)

LBX-6513DS

CorporateFeed


© CommScope 18

Feed Harness Construction (Continued)

Series Feed Center Feed(Hybrid) Corporate Feed

Advantages • Minimum feed losses

• Simple feed system• Frequency

independent main lobe direction

• Reasonably simple feed system

• Frequency independent main beam direction

• More beam shaping ability, sidelobe suppression

Disadvantages

• Not as versatile as corporate (less bandwidth, less beam shaping)

• Complex feed system

BEAMTILT

450 455 460 465 470 MHz+2°

+1°

0°

+1°

+2°

ASP-705


© CommScope 19

• Coaxial cable

– Best isolation

– Constant impedance

– Constant phase

• Microstripline, corporate feeds

– Dielectric substrate

– Air substrate

Feed Networks


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• Dielectric substrate

– Uses printed circuit technology

– Power limitations

– Dielectric substrate causes loss (~1.0 dB/m at 2 GHz)

• Air substrate

– Metal strip spaced above a groundplane

– Minimal solder or welded joints

– Laser cut or punched

– Air substrate cause minimal loss (~0.1 dB/m at 2 GHz)

Microstrip Feed Lines


© CommScope 21

Air Microstrip Network


© CommScope 22

LBX-3316-VTM Using Hybrid Cable/Air Stripline


© CommScope 23

LBX-3319-VTM Using Hybrid Cable/Air Stripline


© CommScope 24

DB812 Omni Antenna

Vertical Pattern


© CommScope 25

Pattern Simulation

932DG65T2E-M


© CommScope 26

For sector antenna, the key pattern objective is to focus as much energy as possible into a desired sector with a desired radius while minimizing unwanted interference to/from all other sectors.

This requires:

• Optimized pattern shaping

• Pattern consistency over the rated frequency band

• Pattern consistency for polarization diversity models

• Downtilt consistency

Key Antenna Pattern Objectives


© CommScope 27

What is it?The main lobe is the radiation pattern lobe that contains the majority portion of radiated energy.

Why is it useful?Shaping of the pattern allows the contained coverage necessary for interference-limited system designs.

How is it measured?The main lobe is characterized using a number of the measurements which will follow.

What is Andrew standard?Andrew conforms to the industry standard.

Main Lobe

35° Total35° TotalMain LobeMain Lobe


© CommScope 28

What is it?The angular span between the half-power (-3 dB) points measured on the cut of the antenna’s main lobe radiation pattern.

Why is it useful?It allows system designers to choose the optimum characteristics for coverage vs. interference requirements.

How is it measured?It is measured using data collected from antenna range testing.


Horizontal And Vertical1/2 Power1/2 PowerBeamwidthBeamwidth

30 30

Half-Power Beamwidth


© CommScope 29

What is it?The ratio in dB of the maximum directivity of an antenna to its directivity in a specified rearward direction. Note that on a dual-polarized antenna, it is the sum of co-pol and cross-pol patterns.

Why is it useful?It characterizes unwanted interference on the backside of the main lobe. The larger the number, the better!


What is Andrew standard?Each data sheet shows specific performance. In general, traditional dipole and patch elements will yield 23–28 dB while the Directed Dipole™ style elements will yield 35–40 dB.

F/B Ratio @ 180 degreesF/B Ratio @ 180 degrees0 dB – 25 dB = 25 dB0 dB – 25 dB = 25 dB

Front-To-Back Ratio


© CommScope 30

What is it?Sidelobe level is a measure of a particular sidelobe or angular group of sidelobes with respect to the main lobe.

Why is it useful?Sidelobe level or pattern shaping allows the minor lobe energy to be tailored to the antenna’s intended use. See Null Fill and Upper Sidelobe Suppression.

How is it measured?It is always measured with respect to the main lobe in dB.


Sidelobe LevelSidelobe Level(–20 dB)(–20 dB)

Sidelobe Level


© CommScope 31

What is it?Null filling is an array optimization techniquethat reduces the null between the lower lobes in the elevation plane.

Why is it useful?For arrays with a narrow vertical beam-width (less than 12°), null filling significantly improves signal intensity in all coverage targets below the horizon.

How is it measured?Null fill is easiest explained as the relative dB difference between the peakof the main beam and the depth of the 1st lower null.

What is Andrew standard?Most Andrew arrays will have null fill of 20–30 dB without optimization. To qualify as null fill, we expect no less than 15 and typically 10–12 dB!

Null Filling


© CommScope 32

Null Filled to 16 dB Below Peak

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-100

-80

-60

-40

-20

0

Distance (km)

Rec

eive

d Le

vel (

dBm

)

Transmit Power = 1 W

Base Station Antenna Height = 40 m

Base Station Antenna Gain = 16 dBd

Elevation Beamwidth = 6.5°

Important For Antennas With Narrow Elevation Beamwidths

Null Filling


© CommScope 33

What is it?Upper sidelobe suppression (USLS) is an array optimization technique that reduces the undesirable sidelobes above the main lobe.

Why is it useful?For arrays with a narrow vertical beamwidth (less than 12°), USLS can significantly reduce interference due to multi-path or when the antenna is mechanically downtilted.

How is it measured?USLS is the relative dB difference between the peak of the main beam peak of the first upper sidelobe.

What is Andrew standard?Most of Andrew’s arrays will have USLS of >15 dB without optimization. The goal of all new designs is to suppress the first upper sidelobe to unity gain or lower.

Upper Sidelobe Suppression

First UpperSidelobeSuppression


© CommScope 34

What is it?The ability of an antenna to discriminate between two waves whose polarization difference is 90 degrees.

Why is it useful?Orthogonal arrays within a single antenna allow for polarization diversity. (As opposed to spacial diversity.)

How is it measured?The difference between the co-polar pattern and the cross-polar pattern, usually measured in the boresite (the direction of the main signal).


= 0°, XPol = – dB= 5°, XPol = –21 dB=10°, XPol = –15 dB=15°, XPol = –11 dB=20°, XPol = –9 dB=45°, XPol = –3 dB =50°, XPol = –2.3 dB =60°, XPol = –1.2 dB =70°, XPol = –0.54 dB =80°, XPol = –0.13 dB =90°, XPol = 0 dBXPol = 20 log ( sin ()

Orthogonality

Decorrelation between the Green and Blue Lines


© CommScope 35

120°

Typical

120°

Directed Dipole™

What is Andrew standard?For traditional dipoles, the minimum is 10 dB; however, for the Directed Dipole™ style elements, it increases to 15 dB min.

What is it?CPR is a comparison of the co-pol vs. cross-pol pattern performance of a dual-polarized antenna generally over the sector of interest (alternatively over the 3 dB beamwidth).

Why is it useful?It is a measure of the ability of a cross-pol array to distinguish between orthogonal waves. The better the CPR, the better the performance of polarization diversity.

How is it measured?It is measured using data collected from antenna range testing and compares the two plots in dB over the specified angular range. Note: in the rear hemisphere, cross-pol becomes co-pol and vice versa.

Co-Polarization

Cross-Polarization (Source @ 90°)

Cross-Pol Ratio (CPR)


© CommScope 36

What is it?It refers to the beam tracking between the two beams of a +/–45° polarization diversity antenna over a specified angular range.

Why is it useful?For optimum diversity performance, the beams should track as closely as possible.

How is it measured?It is measured using data collected from antenna range testing and compares the two plots in dB over the specified angular range.

+45°–45°Array Array

120°120°

Horizontal Beam Tracking

What is Andrew standard?The Andrew beam tracking standard is +/–1 dB over the 3 dB horizontal beamwidth.


© CommScope 37

–3 dB +3 dB

SquintSquintθ/2

θ

HorizontalBoresiteWhat is it?

The amount of pointing error of a given beam referenced to mechanical boresite.

Why is it useful?The beam squint can affect the sector coverage if it is not at mechanical boresite. It can also affect the performance of the polarization diversity style antennas if the two arrays do not have similar patterns.


What is Andrew standard?For the horizontal beam, squint shall be less than 10% of the 3 dB beamwidth. For the vertical beam, squint shall be less than 15% of the 3 dB beamwidth or 1 degree, whichever is greatest.

Beam Squint


© CommScope 38

What is it?SPR is a ratio expressed in percentage of the power outside the desired sectorto the power inside the desired sector created by an antenna’s pattern.

Why is it useful?It is a percentage that allows comparison of various antennas. The better the SPR, the better the interference performance of the system.

How is it measured?It is mathematically derived from the measured range data.

What is Andrew standard?Andrew Directed Dipole™ style antennas have SPR’s typically less than 2 percent.

Sector Power Ratio (SPR)

PUndesired

SPR (%) = X 100

PDesired

300

60Σ60

300Σ

120°120°

Desired

Undesired


© CommScope 39

83°

60°Area of Poor Silence with

>27 dB Front-to-Back Ratio

Standard 85° Panel Antenna

74°

120°Cone of Great Silence with >40 dB Front-to-Back Ratio

932LG

Directed Dipole™

–16 dB –12 dB

HorizontalAnt/AntIsolation

Roll offat -/+ 60°

–7 dB –6 dB

-10 dBpoints

74° 83°

Next SectorAnt/AntIsolation–35 dB –18 dB

Coneof Silence

Key Antenna Parameters To Examine Closely

Antenna–Based System Improvements


© CommScope 40

Ratings:

1 = Always important

2 = Sometimes important

3 = Seldom important

Azimuth Beam

• Beam tracking vs. frequencyLimited to sub-bands on broadband models

• Squint

• Roll-off past the 3 dB points

• Front-to-back ratio

• Cross-pol beam tracking

Elevation Beam

• Beam tracking vs. frequency

• Upper sidelobe suppression

• Lower null fill

• Cross-pol beam tracking

Key Antenna Pattern Objectives

UrbanSuburban

Rural

1 1 1

1 1 1

1 2 3

1 1 2

1 1 1

1 2 3

1 2 3

3 3 2

2 2 3


© CommScope 41

Ratings:

1 = Always important

2 = Sometimes important

3 = Seldom important

Downtilt

• Electrical vs. mechanical tilt

• Absolute tilt

• Electrical tilt vs. frequency

• Effective gain on the horizon

Gain

• Close to the theoretical value

(directivity minus losses)

Note: Pattern shaping reduces gain.

Key Antenna Pattern Objectives (Continued)

UrbanSuburban

Rural

1 1 3

2 2 3

1 2 3

1 2 3

2 1 1


© CommScope 42

Adaptive Array (AA)

• Planar array

• External digital signal processing (DSP) controls the antenna pattern

• A unique beam tracks each mobile

• Adaptive nulling of interfering signals

• Increased signal to interference ratio performance benefits

Advanced Antenna Technology

• 4, 6, and 8 column vertical pol designs for WiMAX and TD-SCDMA*

• Often calibration ports are used

* Time Division Spatial Code Division Multiple Access


© CommScope 43

MIMO Systems

2 x 2 MIMO Spatial Multiplexing

• Multiple Input Multiple Output (MIMO)

• External DSP extracts signal from interference

• Capacity gains due to multiple antennas


• A DualPol® RET for 2x2 MIMO, two separated for 4x4 MIMO

• Spatial multiplexing works best in a multi-path environment

• Space Time Block Coding is a diversity MIMO mode


© CommScope 44

SmartBeam® Antenna Family


• Most flexible and efficient antenna system in the industry

• Solution for the traffic peaks instead of raising the bar everywhere

• Full 3-way remote optimization options- RET – Remote Electrical Tilt (e.g. 0–10°)- RAS – Remote Azimuth Steering (+/– 30°)- RAB – Remote Azimuth Beamwidth (from 35° to 105°)

• Redirect and widen the beam based on traffic requirements

• Balance the traffic per area with the capacity per sector

• Best utilization of radio capacity per sector

• Convenient and low-cost optimization from a remote office

• Quick and immediate execution

• Scheduled and executed several times a day (e.g. business and residential plan)


© CommScope 45

35° 65°

90° 105°


SmartBeam®

3-Way Model

Azimuth patterns measured at 1710–2180 MHz with no radome.


© CommScope 46

35° 65°

90° 105°


SmartBeam®

3-Way Model

Elevation patterns measured at 1710–2180 MHz with no radome.


© CommScope 47

• Choosing sector antennas

• Narrow beam antenna applications

• Polarization—vertical vs. slant 45°

• Downtilt—electrical vs. mechanical

• RET optimization

• Passive intermodulation (PIM)

• Return loss through coax

• Antenna isolation

• Pattern distortion

System Issues


© CommScope 48

For 3 sector cell sites, what performance differences can be expected

from the use of antennas with different horizontal apertures?

Criteria

• Area of service indifference between adjacent sectors (ping-pong area)

• For comparison, use 6 dB differentials

• Antenna gain and overall sector coverage comparisons

Choosing Sector Antennas


© CommScope 49

-40

-35

-30

-25

-20

-15

-10

-5

0

120° Horizontal Overlay Pattern

DB874H120DB878H120

Examples

Low Band

3 x 120° Antennas

VPol

3 dB

49°49°


© CommScope 50

-40

-35

-30

-25

-20

-15

-10

-5

0

5 dB

90° Horizontal Overlay Pattern

Examples

DB854DG90 DB842H90DB856DG90 DB844H90DB858DG90 DB848H90LBX-9012 LBV-9012LBX-9013

Low Band

High Band

XPol VPol

3 x 90° Antennas

44°44°

DB932DG90 UMW-9015 DB950G85HBX-9016UMWD-09014B UMWD-09016


© CommScope 51

65° Horizontal Overlay Pattern Examples

CTSDG-06513 DB844H65CTSDG-06515 DB848H65CTSDG-06516 LBV-6513DB854DG65DB856DG65DB858DG65LBX-6513LBX-6516

Low Band

High Band

XPol VPol

3 x 65° Antennas

-40

-35

-30

-25

-20

-15

-10

-5

0

19°19°

10 dB

UMWD-06513 PCS-06509 UMWD-06516 HBV-6516 UMWD-06517 HBV-6517HBX-6516HBX-6517


© CommScope 52

6-Sector Site (33°)

Rural Roadway

Repeater

Narrow Donor, Wide Coverage

Antennas

Road

4-Sector Site (45°)

Special Narrow Beam Applications


© CommScope 53

Test Drive Route

MOCKIN

GBIRD L

ANE

RE

GA

L R

OW

HARRY HINES

STEMM

ONS FRWY

AIRPORT FRWY.

INW

OOD ROAD

MOTOR S

TREET

35

183

CELL SITE

N


© CommScope 54

Polarization Diversity Tests

Test A

.

Test B

1 2

DRIVE TESTS

HANDHELD

MOBILE

1A 2A

1B 2B

A

B

+45°/-45° 0°/90°(Slant 45°) (H/V)

DB854HV90

DB854DD90


© CommScope 55

TEST 1ATEST 1A

Slant 45° / Hand-Held In Car

Space Diversity vs. Slanted +45°/–45°Test Set-Up and Uplink Signal Strength Measurements

-40

Vert Left

Vert Right

Slant Div

SlantDiv

UplinkSignal Strength

Sig

nal

Str

eng

th (

dB

m)

-50

-60

-70

-80

-90

-100

moving awayfrom tower

moving towardstower

moving crossface

EE

9dB9dB

7.5 ft.7.5 ft.

AA BB

DB854DD90DB833 DB833

9dB9dB

RedRed BlueBlue

11dB11dB

GreenGreen

BlackBlack


© CommScope 56

Difference Between Polarization Diversity and Space DiversityAverage Difference

-8

-4

0

4

8

12

16S

ign

al S

tren

gth

(d

B)

Difference Between Strongest Uplink Signals

Slant 45° / Hand-Held In Car

Space Diversity vs. Slanted +45°/–45° TEST 1ATEST 1A

Slant ±45° Improvement


© CommScope 57

Slant 45° / Mobile With Glass MountSpace Diversity vs. Slanted +45°/-45°

-40Test Set-Up and Uplink Signal Strength Measurements

Vert Left

Vert Right

Slant Div

SlantDiv

UplinkSignal Strength

Sig

nal

Str

eng

th (

dB

m)

-90

11dB11dB

GreenGreen

BlackBlack-50

-60

-70

-80

EE

9dB9dB

7.5 ft.7.5 ft.

AA BB

DB854DD90DB833 DB833

moving awayfrom tower

moving towardstower

moving crossface

9dB9dB

RedRed BlueBlue

TEST 1BTEST 1B


© CommScope 58

Difference Between Polarization Diversity and Space DiversityAverage Difference

Difference Between Strongest Uplink Signals16

-8

-4

0

4

8

12

Sig

nal

Str

eng

th (

dB

)

TEST 1BTEST 1B

Slant 45° / Mobile With Glass Mount

Space Diversity vs. Slanted +45°/-45°

Slant ±45° Degradation


© CommScope 59

Rysavy Research


© CommScope 60

Future Technology Focus

• Figure 16 shows that HSDPA,1xEV-DO, and 802.16e are all within 2-3 dB of the Shannon bound, indicating that from a link layer perspective, there is not much room for improvement.

• This figure demonstrates that the focus of future technology enhancements should be on improving system performance aspects that improve and maximize the experienced SNRs in the system instead of investigating new air interfaces that attempt to improve the link layer performance. 1 Peter Rysavy of Rysavy Research, “Data Capabilities: GPRS to HSDPA and

Beyond”, 3G Americas, September 2005


© CommScope 61

Lower Co-Channel Interference/Better Capacity And Quality

The rapid roll-off of the lower lobes of the Andrew Directed Dipole™ antennas create larger, better defined ‘cones of silence’ behind the array.

• Much smaller softer hand-off area

• Dramatic call quality improvement

• 5%–10% capacity enhancement

Andrew Directed Dipole™

In a three sector site, traditional antennas produce a high degree of imperfect power control or sector overlap.

Imperfect sectorization presents opportunities for:

• Increased softer hand-offs

• Interfering signals

• Dropped calls

• Reduced capacity

Traditional Flat Panels

65° 90°

65°

The Impact

90°


© CommScope 62

On the Capacity and Outage Probability of a CDMA Heirarchial Mobile System with Perfect/Imperfect Power Control and SectorizationBy: Jie ZHOU et, al IEICE TRANS FUNDAMENTALS, VOL.E82-A, NO.7 JULY 1999

. . . From the numerical results, the user capacities are dramatically decreased as the imperfect power control increases and the overlap between the sectors (imperfect sectorization) increases . . .

Effect of Soft and Softer Handoffs on CDMA System CapacityBy: Chin-Chun Lee et, al IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 47, NO. 3, AUGUST 1998

Qualitatively, excessive overlay also reduces capacity of TDMA and GSM systems.

Overlapping angle in degree

Per

cen

tag

e o

fca

pac

ity

loss

0 5 10 15

5

10

15

0

120° Sector Overlay Issues


© CommScope 63

Hard, Soft, and Softer Handoffs

• Hard Handoff- Used in time division multiplex systems

- Switches from one frequency to another

- Often results in a ping-pong switching effect

• Soft Handoff- Used in code division multiplex systems

- Incorporates a rake receiver to combine signals from multiple cells

- Smoother communication without the clicks typical in hard handoffs

• Softer Handoff- Similar to soft handoff except combines signals from multiple adjacent

sectors


© CommScope 64

Soft and Softer Handoff Examples

Softer Handoff

Two-Way Soft Handoff

Three-Way Soft Handoff


© CommScope 65

In urban areas, service and frequency utilization are frequently improved

by directing maximum radiation power at an area below the horizon.

This technique . . .

• Improves coverage of open areas close to the base station.

• Allows more effective penetration of nearby buildings, particular

high-traffic lower levels and garages.

• Permits the use of adjacent frequencies in the same general region.

Beam Downtilt


© CommScope 66

• Mechanical downtilt lowers main beam, raises back lobe.

• Electrical downtilt lowers main beam and lowers back lobe.

• A combination of equal electrical and mechanical downtilts

lowers main beam and brings back lobe onto the horizon!

Electrical/Mechanical Downtilt


© CommScope 67

Mechanical Electrical

Electrical/Mechanical Downtilt (Continued)


© CommScope 68

DB5083 downtilt mounting kit is

constructed of heavy duty galvanized

steel, designed for pipe mounting

12” to 20” wide panel antennas.

• Correct bracket calibration assumes a plumb mounting pipe!

• Check antenna with a digital level.

DB5083 Downtilt Mounting Kit


© CommScope 69

Mechanical tilt causes . . .

• Beam peak to tilt below horizon

• Back lobe to tilt above horizon

• At ± 90°, no tilt

Pattern Analogy—Rotating A Disk

Mechanical Downtilt


© CommScope 70

8°0° 10°6°4°Mechanical Tilt

0

10

20

30

40

50

6070

8090100110

120

130

140

150

160

170

180

190

200

210

220

230

240250

260 270 280290

300

310

320

330

340

350

Elevation Pattern

0

10

20

30

40

50

6070

8090100110

120130

140

150

160

170

180

190

200

210

220

230

240250

260 270 280290

300

310

320

330

340

350

Azimuth Pattern

Mechanical Downtilt Coverage


© CommScope 71

85°

Quiz What is the vertical beamwidth of a 4-element array?

0° Mechanical Downtilt


© CommScope 72

93°



© CommScope 73

123°



© CommScope 74

Horizontal 3 dB Bandwidth Undefined



© CommScope 75

• For the radiation pattern to show maximum gain in the direction of the horizon, each stacked dipole must be fed from the signal source in phase.

• Feeding vertically arranged dipoles out of phase will generate patterns that look up or look down.

• The degree of beam tilt is a function of the phase shift of one dipole relative to the adjacent dipole.

Dipoles Fed In Phase

Exciter

Phase

Energy

in

Dipoles Fed Out of Phase

Wave

Fro

nt

Exciter

Generating Beam Tilt

Managing Beam Tilt


© CommScope 76

Cone of the Beam Peak Pattern

Electrical tilt causes . . .

• Beam peak to tilt below horizon

• Back lobe to tilt below horizon

• At ± 90°, tilt below horizon

• All the pattern tilts

Pattern Analogy—Forming A Cone Out Of A Disk

Electrical Downtilt


© CommScope 77

8°0° 10°6°4°Electrical Tilt

0

10

20

30

40

50

6070

8090100110

120

130

140

150

160

170

180

190

200

210

220

230

240250

260 270 280290

300

310

320

330

340

350

Elevation Pattern

0

10

20

30

40

50

6070

8090100110

120

130

140

150

160

170

180

190

200

210

220

230

240250

260 270 280290

300

310

320

330

340

350

Azimuth Pattern

Electrical Downtilt Coverage


© CommScope 79

Optimization

Remote Electrical Downtilt (RET)

ATM200-002RET Device (Actuator)

Network Server

ATC300-1000Rack Mount Controller

ANMS™

Local PC

ATC200-LITE-USBPortable Controller

Remote Locations

Local PC


© CommScope 81

TxF1

TxF2

RxF3

F2

F1

Receiver-Produced

TxF1

TxF2

RxF3

F3

F2

Transmitter-Produced

Rx3

DUPTx1

Tx2

COMB

F3

F1

F2

RF Path-Produced

RxF3

Tx1

Tx2

F1

F2

F3

Elsewhere

Where?

Intermod Interference


© CommScope 82

1 1 Second 1F1 + 1F2 38751F1 – 1F2 15

2 1 Third 2F1 + 1F2 5820*2F1 – 1F2 1960

1 2 Third 2F2 + 1F1 5805*2F2 – 1F1 1915

2 2 Fourth 2F1 + 2F2 77502F1 – 2F2 30

3 2 Fifth 3F1 + 2F2 9695*3F1 – 2F2 1975

2 3 Fifth 3F2 + 2F1 9680*3F2 – 2F1 1900

Product Product Productn m Order Formula Frequencies (MHz)

FIM = nF1 ± mF2

Example: F1 = 1945 MHz; F2 = 1930 MHz

*Odd-order difference products fall in-band.

Product Frequencies, Two-Signal IM

High Band


© CommScope 83

Odd-Order Difference Products

Two-Signal IM

Example: F1 = 1945 MHz; F2 = 1930 MHz

ΔF = F1 - F2 = 15

Third Order: F1 + ΔF; F2 - ΔF

Fifth Order: F1 + 2ΔF; F2 - 2ΔF

Seventh Order: F1 + 3ΔF; F2 - 3ΔF

Higher than the highest – lower than the lowest – none in-between

ΔF

5th

3F2 – 2F1

1900

F2

F2

1930

F1

F1

1945

3rd

2F1 – F2

1960

5th

3F1 – 2F2

1975

3rd

2F2 – F1

1915ΔF ΔF

dBc

dBm

2ΔF 2ΔF


© CommScope 84

11th1855

9th1870

7th1885

5th1900

3rd1915 1930 1945

Channel BandwidthBlock (MHz) Frequencies

C 30 1895–1910, 1975–1990C1 15 1902.5–1910, 1982.5–1990C2 15 1895–1902.5, 1975–1982.5C3 10 1895–1900, 1975–1980C4 10 1900–1905, 1980–1985C5 10 1905–1910, 1985–1990

Note: Some of the original C block licenses (originally 30 MHz each) were split into multiple licenses (C-1 and C-2: 15 MHz; C-3, C-4, and C-5: 10 MHz).

FCC Broadband PCS Band Plan

PCS A Band Intermodulation


© CommScope 85

3rd1895 1935 1975

Channel BandwidthBlock (MHz) Frequencies

C 30 1895–1910, 1975–1990C1 15 1902.5–1910, 1982.5–1990C2 15 1895–1902.5, 1975–-1982.5C3 10 1895–1900, 1975–1980C4 10 1900–1905, 1980–1985C5 10 1905–1910, 1985–1990

Note: Some of the original C block licenses (originally 30 MHz each) were split into multiple licenses (C-1 and C-2: 15 MHz; C-3, C-4, and C-5: 10 MHz).

FCC Broadband PCS Band Plan

PCS A & F Band Intermodulation


© CommScope 86

• Ferromagnetic materials in the current path:- Steel

- Nickel plating or underplating

• Current disruption:- Loosely contacting surfaces

- Non-conductive oxide layers between contact surfaces

Causes Of IMD


© CommScope 87

700, 750, 850A&B, PCS & AWS polarization diversity

DBXNH-6565A-VTM

|||||

850

|||||

850

850 AWS

TMA

Triplex Lo/Mid/Hi

Triplex Lo/Mid/Hi

PCS

LNX-6512DS-VTM

750 Upper C

DBXNH-6565A-VTM

850

X

X

X

X

X

4 antennas and 4

transmission lines

850 A+A’+A’’

850

X

X

X

X

X

LNX-6512DS-VTMX

X

X

X

X

PCS 700

700 Lower A & B

Triplex Lo/Mid/Hi

Triplex Lo/Mid/Hi

AWS

X

X

X

AWS750

Triplex Lo/Mid/Hi

Triplex Lo/Mid/Hi

Triplex Lo/Mid/Hi

Triplex Lo/Mid/Hi

X

X

TMA

850 B+B’

TMA


© CommScope 88

FIM = F1 + F2 –F3

*Odd-order difference products fall in-band.

Product Frequencies, Three-Signal IM

Upper 700 C / 850 A expanded

F1 MHz

F2 MHz

F3 MHz

Product Order

Product Formula Product MHz

755 890 869 Third 1F1+1F2+1F3 776

757 890 871 Third 1F1+1F2+1F3 776

869 869 891.5 Third 1F1+1F2+1F3 846.5

757 891.5 872.5 Third 1F1+1F2+1F3 776

757 891.5 869.5 Third 1F1+1F2+1F3 779


© CommScope 89

System VSWR CalculatorSystem VSWR Calculator

Version 9.0

Frequency (MHz): 850.00 18-Mar-09

System Component Max. VSWRReturn

Loss (dB)

Cable Type / Component Loss (dB)

Cable Length

(m)

Cable Length (ft)

Ins Loss w/2 Conn

(dB)

% of Est. System

Reflection

Reflections at input

Antenna or Load 1.50 13.98 87.2% 0.10032 2 Jumper 1.05 32.26 2 1.83 6.00 0.00 0.0% 0.00002 2 Tower Mounted Amp 1.20 20.83 0.20 0.00 0.0% 0.00002 2 Jumper 1.09 27.32 2 1.83 6.00 0.00 0.0% 0.00002 2 Top Diplexer or Bias Tee 1.15 23.13 0.20 0.00 0.0% 0.00002 2 Jumper 1.09 27.32 2.00 1.83 6.00 0.00 0.0% 0.00002 2 Main Feed Line 1.07 29.42 8 200.00 656.17 0.00 0.0% 0.00002 2 Jumper 1.09 27.32 4 30.48 100.00 0.00 0.0% 0.00002 2 Bias Tee 1.15 23.13 0.10 11.00 36.09 0.00 0.0% 0.00002 2 Jumper 1.09 27.32 2.00 1.83 6.00 0.00 0.0% 0.00002 2 Surge Suppressor 1.07 29.42 0.10 0.00 0.0% 0.00002 2 Jumper 1.09 27.32 3.00 1.83 6.00 0.00 0.0% 0.00002 2 Bottom Diplexer or Duplexer 1.20 20.83 0.10 0.00 0.0% 0.00001 1 Jumper 1.08 28.30 1.00 27.30 89.57 3.00 12.8% 0.0385

100.0%

Legacy Jumper / TL Cables Andrew CommScope

1/2 inch Superflexible Copper FSJ4-50B Estimated Conn Loss ( 2per cable) 0.0281/2 inch Foam Copper LDF4-50A CR 540

1/2 inch Superflexible Aluminum SFX 500 Typical System Reflection: 0.10741/2 inch Foam Aluminum FXL 540 Typical System VSWR: 1.24

Typical System Return Loss (dB): 19.4Legacy Transmission Lines Andrew CommScope

7/8 inch Copper LDF5-50A CR 1070 Worst System Reflection: 0.13871 1/4 inch Copper LDF6-50 CR 1480 Worst System VSWR: 1.321 5/8 inch Copper LDF7-50A CR 1873 Worst System Return Loss (dB): 17.2

7/8 inch Very Flexible Copper VXL5-501 1/4 inch Very Flexible Copper VXL6-50 Total Insertion Loss (dB): 3.001 5/8 inch Very Flexible Copper VXL7-50

7/8 inch Virtual Air Copper AVA5-50 Return Loss to VSWR converter Feet to meters converter

Yes 1 5/8 inch Virtual Air Copper AVA7-507/8 inch Aluminum AL5-50 FXL 780

1 1/4 inch Aluminum FXL 1480 17.00 1.33 100.00 30.481 5/8 inch Aluminum AL7-50 FXL 1873

No

meters

Component Used?

Return Loss (dB)

VSWR Feet

LDF4-50A

VXL7-50

No

No

No

No

No

No

No

No

No

No

No

YesYes

No

FSJ4-50B


© CommScope 90

Possible Cascaded VSWR Results

If: L = 1.5:1 (14 dB RL Antenna)

S = 1.2:1 (20.8 dB RL TMA)

Then: X (max) = 1.8:1 (10.9 dB RL)

S (min) = 1.25:1 (19.1 dB RL)

Worst case seldom happens in real life, but

be aware that it is possible!

Possible results (at a given frequency) when Antenna and TMA are interconnected with different electrical

length jumpers.

From http://www.home.agilent.com/agilent/editorial.jspx?cc=US&lc=eng&ckey=895674&nid=-35131.0.00&id=895674


© CommScope 91

Antenna

TMA

6 foot LDF4-50A

12 foot LDF4-50A

20 foot FSJ4-50

Transmission Line

Antenna Return Loss Diagram

12 foot LDF4-50A

20 foot FSJ4-50

Transmission Line

TMA

TMA Return Loss Diagram

Adapter or jumper to bypass TMA

50 ohm load

6 foot LDF4-50A

Recommended Antenna/TMA Qualification Test


© CommScope 92

The values indicated by these curves are approximate because of coupling which exists between the antenna and transmission line. Curves are based on the use of half-wave dipole antennas. The curves will also provide acceptable results for gain type antennas. If values (1) the spacing is measured between the physical center of the tower antennas and it (2) one antenna is mounted directly above the other, with no horizontal offset collinear). No correction factor is required for the antenna gains.

Antenna Spacing in Feet (Meters)

Iso

latio

n in

dB

2000 MHz

850 MHz

450 MHz

160 MHz

75 MHz

40 MHz

Attenuation Provided By VerticalSeparation Of Dipole Antennas


© CommScope 93

Attenuation Provided By HorizontalSeparation Of Dipole Antennas

Antenna Spacing in Feet (Meters)

Iso

latio

n in

dB

2000 MHz

850 MHz

450 MHz

150 MHz

70 MHz

30 MHz50 MHz

Curves are based on the use of half-wave dipole antennas. The curves will also provide acceptable results for gain type antennas if (1) the indicated isolation is reduced by the sum of the antenna gains and (2) the spacing between the gain antennas is at least 50 ft. (15.24 m) (approximately the far field).


© CommScope 94

Conductive (metallic) obstruction in the path of transmit and/or receive antennas may distort antenna radiation patterns in a way that causes systems coverage problems and degradation of communications services.

A few basic precautions will prevent pattern distortions.

Pattern Distortions

Additional information on metal obstructions can also be found online at: www.akpce.com/page2/page2.html


© CommScope 96

Antenna

880 MHz

0°

3½' –10 dB Point

BuildingCorner

Obstruction @ –10 dB Point

90° Horizontal Pattern

340

7

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350

-40

-35

-30

-25

-20

-15

-10

-5

0


© CommScope 97

880 MHz

Antenna

0°

3½'–6 dB Point

BuildingCorner



-40

-35

-30

-25

-20

-15

-10

-5

0340

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350


© CommScope 98

880 MHz

Antenna

0°3½'

–3 dB Point

BuildingCorner



-40

-35

-30

-25

-20

-15

-10

-5

0340

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350


© CommScope 99

880 MHz

Antenna

0°

12

0.51λ Diameter Obstacle @ 0°


-40

-35

-30

-25

-20

-15

-10

-5

0340

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350


© CommScope 100

880 MHz

Antenna

45°



-40

-35

-30

-25

-20

-15

-10

-5

0340

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350


© CommScope 101

880 MHz

Antenna

60°



-40

-35

-30

-25

-20

-15

-10

-5

0340

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350

Additional information on metal obstructions can also be found online at www.akpce.com/page2/page2.html.


© CommScope 102

880 MHz

Antenna

80°



Additional information on metal obstructions can also be found online at www.akpce.com/page2/page2.html.

-40

-35

-30

-25

-20

-15

-10

-5

0340

330

0 1020

30

40

50

60

0

80

90

100

110

120

130

140

150160

170180190200

210

220

230

240

250

260

270

280

290

300

310

320

350


© CommScope 103

Area That Needs To Be Free Of Obstructions (> 0.51λ)

Antenna90° horizontal (3 dB) beamwidth

Maximum Gain

3 dB Point(45°)

6 dB Point(60°)

10 dB Point(80– 90°)

> 12 WL

> 8

WL

> 6 WL

> 3 WLWL

General Rule


© CommScope 104

tan θ =

d = D x tan θtan 1° = 0.01745

for 0° < θ< 10° : tan θ = θ x tan 1°

Note: tan 10° = 0.1763 10 x 0.01745 = 0.1745

dD

dθD

Pattern Distortions


© CommScope 105

–3 dB point θ° below boresite.

–6 dB point 1.35 x θ° below boresite.–10 dB point 1.7x θ° below boresite.

Vertical BeamWidth= 2 x θ°(–3 dB point)

Gain Points Of A Typical Main Lobe

θ°θº

Relative to Maximum GainRelative to Maximum Gain


© CommScope 106

FiberglassPanel

Dim “A”

Non-Conductive Obstructions

Changes In Antenna Performance In The Presence Of:

90° PC

S

An

tenn

a


© CommScope 107

70°

80°

90°

100°

110°

120°

10 2 3 4 5 6 7 8 9 10 11 12

1/4 1/4 1/2 1/2 1 1 2 2 1-1/2 1-1/2 3/4 3/4

Distance of Camouflage (Inches) (Dim. A)

Ho

rizo

nta

l Ap

ert

ure

FIBERGLASSPANEL

DIM “A”

Performance Of 90° PCS AntennaBehind Camouflage (¼" Fiberglass)


© CommScope 108

W/Plain Façade W/Ribbed Façade Without Facade

Performance Of 90° PCS AntennaBehind Camouflage (¼" Fiberglass)

1.2

1.3

1.4

1.5

1.6

1.7

10 2 3 4 5 6 7 8 9 10 11 12

Distance of Camouflage (Inches) (Dim. A)

VS

WR

(W

orst

Cas

e)

FIBERGLASSPANEL

DIM “A”

1/4 1/4 1/2 1/2 1 1 2 2 1-1/2 1-1/2


© CommScope 109

330°

300°

270°

240°

210°

180°

150°

120°

60°

30°

0°

90°

-20

-25

-30

-35

-40

-45

-50

-55

No Fiberglass

90°90°

330°

300°

270°

240°

210°

180°

150°

120°

60°

30°

0°

90°

-20

-25

-30

-35

-40

-45

-50

-15

68°68°

1.5" to Fiberglass

330°

300°

270°

240°

210°

180°

150°

120°

60°

30°

0°

90°

-25

-30

-35

-40

-45

-50

-55

-20

3" to Fiberglass

102°102°

Distance From Fiberglass


© CommScope 110

330°

300°

270°

240°

210°

180°

150°

120°

60°

30°

0°

-20

-25

-30

-35

-40

-45

-50

-15

90°

6" to Fiberglass

112°112°330°

300°

270°

240°

210°

180°

150°

120°

60°

30°

0°

90°

-20

-25

-30

-35

-40

-45

-50

-15

4" to Fiberglass

77°77°

330°

300°

270°

240°

210°

180°

150°

120°

60°

30°

0°

90°

-20

-25

-30

-35

-40

-45

-50

-15

9" to Fiberglass

108°108°

Distance From Fiberglass

bsa antenna theory_mod

Documents

glass mountspace

provide acceptable

hybrid cableair

antenna range

narrow vertical

channel bandwidth

upper sidelobe

gain type