Kaelus PIM Fundamentals

7/21/2019 Kaelus PIM Fundamentals

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Passive Intermodulation Fundamentals

Jay R. Maple

Applications Engineer

303.378.3475


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Global Technology Company

Listed on the London Stock

Exchange

22,000 employees, Active in 50

countries

2010 sales = $5.4 Billion USD

Smiths Group PLC


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Kaelus is global company that designs and manufactures complex andtechnically sophisticated RF products for use in the rapidly growing wireless

communications market.

We are not a new company but the consolidation of some leading industry

brands within Wireless Telecoms: Triasx, Summitek, Allrizon and the commercialdivision of TRAK Microwave Ltd.

New company name


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Summitek Instruments: Denver, CO

Triasx: Brisbane, Australia

Founded in 1995, Acquired by Smiths in 2008

Recognized leader in the design and manufacture of

innovative RF filter based products

Pioneered development of Portable PIM systems with Telstrain Australia in 2004

Partnership with Summitek in 2007

>1000 Portable PIM systems worldwide

Founded in 1996, Acquired by Smiths in 2001

Summiteks primary business is manufacturing Passive

Intermodulation (PIM) test equipment

>800 Bench-top PIM systems worldwide

#1 PIM Test Equipment manufacturer

worldwide.

Test Instrument Heritage


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PIM = Noise generated by Tx signals interacting with

materials in the RF path

PIM = Interference

PIM = Reduced BTS Coverage and Capacity

What is Passive InterModulation (PIM)


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Loose / inconsistent metal to metal contacts

Not enough contact pressure.

Cracked solder joints

Cold solder joints

Scratches or dents at mating interfaces

Burrs

Metal flakes, chips, dust

Improperly formed / sized parts

Misaligned parts

Rough mating surfaces (saw cut)

Loose bolts

Ferromagnetic materials (steel, nickel, etc.)

Contamination

Trapped between mating surfaces

Trapped between plating layers

Surface Oxides.

Anything introducing distortion within the RF path;

What causes PIM?


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MANY unwanted frequencies are generated.

f1

f2

f1+f

2f2-f

1

2f1-f

2

2f1

2f2

2f2-f

13f

2-2f

14f2-3f

1

3f1-2f

24f

1-3f

2

InterferenceInterference

Desired

3rd Order

7th Order

5th Order

The result


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Incident signals

Reflected signals

Transmitted signals

Minimum loss

Minimum

Linear Infrastructure(No new frequencies)

Ideal Infrastructure

Reflections measured by sweep test

Measures the quality of impedance

matching in the system.


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Return Loss Pr PT

-3 dB 50% 50%

-6 dB 25% 75%

-9 dB 12.5% 87.5%

-12 dB 6.3% 93.7%

-15 dB 3.1% 96.9%

-18 dB 1.6% 98.4%

-21 dB 0.8% 99.2%

Return Loss:

Return Loss is a ratio of Power Reflected to Power Transmitted

Has become the standard quality metric to measure installation

quality


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Incident signals

Reflected + interference signals

Transmitted signals

Reflections still measured by sweep test

Interference measured by PIM tester

Non-Linear Infrastructure

(Creates new frequencies)

Non-ideal Infrastructure


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Both tests are important and necessary to insure quality site

construction.

Smiths Group PLC

Sweep test measures efficiency of signal propagation

PIM test measures ability to propagate signals without

generating interference


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Summitek Instruments has been producing bench top

PIM test systems for more than a decade

Summitek has delivered more than 800 BPIM systems

worldwide

These systems have been used by RF equipment

manufacturers to reduce PIM in their component designs

PIM testing is not new!


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Portable PIM test sets were developed in Australia at therequest of Telstra by Summiteks sister division, Triasx

Summitek / Triasx have delivered more than 1000 PPIMsystems worldwide

These systems are being used by network operatorsworldwide to reduce PIM in their RF infrastructure

What is new is the availability of

rugged, portable versions.


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PIM Source

PIM Test Equipment

Low PIM Load

How does a PIM tester work?


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BTS TransmitBTS Receive

F1 F2IM3

A D

Test Tone (5 KHz)

Guard Band

19

45MHz

Transmit tones in

Guard Band frequencies


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-100 dBm

0dBm

0dBc

-143 dBc

=

dBm dBc

Power relative to the carrier levelAbsolute power relative to1mW

CARRIER

PIM

2 x 20 Watts

CARRIER

+43 dBm

PIM

PIM level is expressed in either

dBm or dBc


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PIM level is VERY dependent on test power level

3dB change in PIM level for every 1dB change in

test power

2W not enough power to certify a site

IEC 62037 recommends 2x 20W (+43dBm) test

carriers

-100 dBm

CARRIER

PIM

+43 dBm

20 Watts

0dB

m

CARRIER

PIM

Noise Floor

2 Watts

-130 dBm

+33 dBm

PIM level is meaningless without also

stating the carrier power level


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Light weight (11 lbs)

Battery operated

Highly portable

Able to identify loose connections

Able to find very bad components

However 4W test sets are useful.


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Site

Guy Wires

Steel Tower

Other Sites IMD

RF In-Line Surge Arrestors

Low Grade Antennas Roof Flashing/Vent Hoods

Installation

Poorly torqued connectors

Scratches

Stress Fractures

Contamination

On conduction materials

Dielectric material

Materials

Rust

Ferromagnetic materials

Poor Quality Plating

Test Equipment

Poor Quality Loads Low quality or damaged jumpers,

adapters and connectors

Misc.

Cracked / Cold Solder joints

Contact Pressure

PIM Sources at the cell site:


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Relatively new Portable PIM test

equipment.Portable PIM test equipment enables system level testing to be conducted at the

cell site.

On site PIM testing reveals:

Installation workmanship issues

Components damaged during installation

Components damaged in transit


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Historically, Sweep testing has

been the only method available to

measure installation quality. A low power signal is transmitted into the

system and the magnitude of the reflected

signal is measured

The Tx frequency is stepped across the

operating range of the site and the ratio of

Reflected Power vs. Transmitted Power isdisplayed at each frequency

Sweep testing will identify many defects:

Kinked jumpers, crushed coax

Poorly matched components (Antennas,

Filters)

Sweep testing can not identify PIM problems at

a site

One frequency transmitted at a time

At very low power


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Survey Results

73.4%

5.5%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

PIM problems VSWR problems

Both Sweep testing and PIM testing

are needed to ensure optimum cell

site performance. This is illustrated by test data collected at cell

sites exhibiting poor KPIs

>100 feed lines surveyed

19 operators, 11 countries

Many PIM problems recorded

Few VSWR problems found

The sites were originally commissioned withSweep test equipment so it is no surprise thatthe VSWR results are good


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Survey Results

41.25%

17% 16.25%

62.50%

0%

10%

20%

30%

40%

50%

60%

70%

Feed Cables Jumper

Cables

Antennas Other

Passive

Devices

PIM defects found:

The PIM defects found were primarilydue to workmanship issues at the RFconnections

Many lines had multiple defects

Other Passive Devices with PIM

problems included:

Diplexing filters

Surge Protectors

Bias-Ts

KPI improvements reported on themajority of sites repaired


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High Dropped Call Rate

Significant increase in call drops after a new carrier was added to a

DAS system with PIM problems.

How to recognize PIM problems in

your network:

PIM induced noise

shrinks the effective

cell size.

Gaps in coverage result

in higher dropped call

rate.


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GSM: Elevated Interference on Idle (IOI) channels

High interference levels before

fixing PIM problems.

Decreased interference after fixing

PIM problems.

Increased successful traffic

channel (TCH) allocations

PIM problems corrected


your network:


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CDMA: High Access Channel Utilization


Significant improvement

after fixing PIM.


your network:

BTS is blind to new mobiles trying to access the cell

Not impacting Dropped Call Rate because the call never

initiated on the sector


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High Average Receive Signal Strength Indication (RSSI) differential between Mainand Diversity paths.

Diversity

Main


Rx levels tracking

together


your network:

BTS PIM causing elevated

average noise on the Main

branch

Diversity path not impacted

Key indicator of an internal

interference problem

External interference would

impact both paths equally


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f1

f2

IM3

TX BandRX Band

IM5IM7

IM9 IM9

IM3

IM5IM7

Severity of PIM in your system:

Higher Tx power = higher PIM levels

IM3 increases 3dB for every 1 dB increase in Tx power

Lower order non-linearity = higher PIM level

Frequency combinations:

More operating bands sharing a feeder = higher probability of PIM in a Rx band (e.g.,DAS)

Wider bandwidth signals = higher probability of PIM in the Rx band (LTE)

Low order PIM in a Rx band = high noise rise


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Metal flake

11th Order-93 dBm

9th

Order

7th Order

5th Order3rd Order

-60 dBm

Outside

PCS Rxband for F1

& F2

selected

Spectrum Analyzer Mode

PIM Severity:

Higher order products can be quite severe!

Repairing IM3 reduces ALL IM products.


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Resistive loads

generate PIM


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90 connectors

typically not as

good as straightconnectors.


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RF Connector Selection:

Avoid using Type-N

7-16 DIN connectors are more robust and produce less PIM


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Poor cable

preparation

Dirt / trash


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Poor cablepreparation


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Poor cable

preparation


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Cable damage


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Passing a static PIM test does not necessarily insure long term performance

Lightly tap RF connections

Flex cables while holding connector fixed

If PIM level jumps out of specification make repairs

Find problems before Mother Nature does!

Wind induced vibration

Temperature variations

PIM testing should be dynamic


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1 2

PIM displayed

PIM Source #1

PIM Source #2

Largest PIM

generator may mask

smaller sources.

Multiple PIM Sources


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1 2

PIM displayed

PIM Source #1

PIM Source #2

Larger PIM sourcemust be removed

before lower level

source can be seen.

Multiple PIM Sources

PIM sources can be external


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Incident signalsTransmitted signals

Reflected + interference signals

Linear Infrastructure

PIM

PIM sources can be external

to the system!


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External PIM Sources

Typical 65 Beamwidth


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4 ft. (1.2m)

800MHz

8 ft. (2.4m)

800MHzEnd View

(Azimuth Pattern)Side View

(Elevation Pattern)

Typical 65 Beamwidth

Antenna Patterns

If t l PIM i t d


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PIM PIM

45 Rotation

If external PIM is suspected,

rotate antenna on mast.

El ti tilti b ff ti


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PIMPIM

15 Rotation

Elevation tilting may be more effective

to identify external PIM sources.

E l PIM S


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External PIM Sources

A t T ti


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Make sure there are no PIM sources within

the field of view of the antenna!

Recommendations: PIMPIM

PIM

SKY

SKY

Antenna Testing

BE SAFE!

Point antenna toward the sky

No metal objects within the half-powerbeam widths of the antenna in both Azimuthand Elevation

Antenna should be placed on non-metallicsupports during test

Test equipment and test operators should belocated off the end of the antenna; not theside

Use a known good antenna to verify thetest environment before testing

A t T ti


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Antenna Testing


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The Benefit

Rx Noise floor

before PIM

testing

5dB reduction in

Rx Noise floor

after correcting

PIM problems.


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1dB improvement in receiver sensitivity canmean as much as 11% fewer radio basestations

Source

Harri Holma and Antii Toskala, WCDMA & UTMS Nokia

Finland 2004. publisher John Wiley and Son USA


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Held calls before

PIM testingIncreased held

calls after

reconstruction

using PIM tester

S mmar


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PIM = reduces site performance

PIM sources can be eliminated / minimized through:

Careful construction techniques

Use of low PIM components

Careful site design

PIM testing should be dynamic (not static)

PIM testing AND VSWR testing are needed to verify system performance

Summary


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Break

PIM test equipment: iHA Series


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Highly portable

Battery operated

2x 2W test tones

Fixed frequencies

Useful for component

testing / fault finding

PIM test equipment: iHA Series

PIM test equipment: iMT Series:


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High Power - Economy

2x 20W test tones

Fixed frequencies

Rugged construction

Integrated transit case

Laptop interface for

reporting

New iMT-850B

PIM test equipment: iMT Series:

PIM test equipment: iQA Series:


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High Power - Premium

Adjustable power (2 20W)

Adjustable frequencies

Rugged construction

Integrated transit case

Panel PC with touch screen interface,

on-board reporting

PIM test equipment: iQA Series:

Accessory Kits:


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Transit case

Jumper cables

Adapters

Wrench

Torque Wrench

Low PIM load

PIM source

Cleaning kit

iQA-130A Soft Case iQA-110A Hard Case

Accessory Kits:

iQA Series


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iQA Series

Precautions


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Precautions

iQA Physical Characteristics


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Telescopinghandle

Cooling fans2 on sides

4 internal

WheelsStorage pouch

Fold-out legs for

bench use.

Shock mounted

electronics

Rugged case

360 air inlet filter

surrounding

electronics

iQA Physical Characteristics

iQA User Interface


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5

3

4

6

7

2

1

iQA User Interface

iQA Software


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iQA Software

8

9 10 11 12

13

15 16 14

17

18

19

20

USER

SCREEN

iQA Software Additional


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Time TraceSpectrum Analyzer

Frequency Sweep

Q

User Modes

iQA Software - Reports


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iQA Software - Reports

Build final site report as you go

No post processing of data required

Output finished report from the iQA in

.PDF format

Screen shot pictures available for

engineering reports

iMT series


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iMT series

iMT Physical Characteristics


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Telescopinghandle

Internal

Cooling fans

Wheels

Rugged,

integrated

transit case

Weather

resistant seal

iMT Physical Characteristics

iMT User Interface


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1

4

2

3

86 5 7

10 9

iMT User Interface

iMT Software


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Remote Terminal Application loaded on

Laptop Computer.

iMT Software

Very similar to iQA software

Serial connection between laptop & iMT

Laptop controls iMT operation

Reports stored directly to laptop computer

iHA Series


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iHA Series

iHA Series


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Alarm

LEDs

RF Output

Port

Measurement

Level LEDs

RF ON

indicator

RF on button Battery Check

Display Mode

iHA Series

Verification Procedure


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Verification Procedure


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2011 Kaelus Inc. All Rights Reserved

www.kaelus.com

Contact Us:

Americas

+1.303.768.8080

Asia Pacific, Africa

+61.(0).7.3907.1200

China

+86.21.5219.2719

Europe, Middle East, India

+44.(0).1383.410386


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Thank you

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