Passive Intermodulation (PIM), an interference challenge for the radio Passive Intermodulation (PIM), an interference challenge for the radio Passive Intermodulation (PIM), an interference challenge for the radio Passive Intermodulation (PIM), an interference challenge for the radio access networksaccess networksaccess networksaccess networks

John Miller

� Kaelus is a new name company within the Smiths Interconnect group

� We are a global company that designs and manufactures complex and technically sophisticated RF products for use in the rapidly growing wireless communications market.

� Kaelus is the consolidation of four leading industry brands within

Smiths Interconnect

� Kaelus is the consolidation of four leading industry brands within Wireless Telecoms: Triasx, Summitek, Allrizon and the commercial division of TRAK Microwave Ltd.

Global Technical Service & Support

AMERICAS : EMEA: APAC :

What is Passive Intermodulation (PIM)?

What is Passive Intermodulation (PIM) ?

PIM = Noise generated by the interaction between th e multiple Tx signals and passive non-linear junctions in the RF path.

f1 f2

2f1-f2 2f2-f13f2-2f13f1-2f2

InterferenceInterference

Desired

Increasing the received Noise floor thus reducing b ase station sites coverage and capacity.

f1+f2f2-f12f1 2f2

3f2-2f14f2-3f13f1-2f2

4f1-3f2

PIM generated products will affect received band (U L) by

PIM is getting more complex with

Networks evolution towards :

• Indoor or outdoor complex DAS systems (shared by several operators)

Load

1800/WC

DM

A

900/1800

Triplexer

RF Output ports

PSPS

PSPS

PSPS

PSPSOutdoor

area

AntAnt

AntAnt

AntAnt

PSPS

AntAnt

AntAnt

Ant

PSPS

PSPS

AntAnt

PSPS

AntAnt

AntAnt

AntAnt

PSPSAntAnt

PSPSAntAnt

PSPSAntAnt

PSPS

AntAnt

IndoorArea 1

IndoorArea 2

IndoorArea 3

IndoorArea 4

IndoorArea 5

• Site sharing with multiple transmit carriers (same RF infrastructure for multiple operators)

• Multi-technology sites (GSM 900 MHz, GSM 1800 MHz, UMTS 2100 and UMTS900 MHz, CDMA 450, CDMA850, LTE800, LTE2600, LTE2300)

Combining UnitGSM 900GSM 1800WCDMA

OP

1B

TS

OP

2B

TS

OP

3B

TS

OP

1B

TS

OP

2B

TS

OP

3B

TS

OP

1N

ode

B

OP

2N

ode

B

OP

3N

ode

B

RF Output ports

PIM Sources

Non-linear metal-to-metal contacts :

• Loose RF connectors.

• Poorly prepared RF cable terminations

• Improperly mated / misaligned parts

• Cracked / cold solder joints

• Loose mechanical fasteners (screws, rivets)

Traditional sweep (RL or DTF) testing many times do es not identify these problems.

Sweep testing vs. PIM testing:

Incident signals Transmitted signalsNon-Linear Infrastructure

Reflected + interference

signals

Reflections caused by changes in impedance are measured using sweep test equipment. (Efficiency of the signal propagation)

Interference caused by non-linear junctions are measured by PIM test equipment

(Interference created by the signal propagation)

� First edition of IEC 62037 was published on 9/16/1999. (>12 years

ago!)

� Purpose:

� To establish a standard test method for measuring Passive

Intermodulation (PIM)

� Provide a method to compare the PIM performance of different devices

� Key recommendations of the specification:

PIM test specification IEC 62037

� Key recommendations of the specification:

� Third Order IM products typically represent the worst case condition of

unwanted signals; therefore measuring IM3 characterizes the DUT

� PIM comparisons should be done at the same power level. (2x 20 W

recommended for mobile communications systems)

� Devices should be subjected to an “impact” or “movement” while PIM

testing

How to test PIM?

PIM Source

PIM

TX 1

TX 2

TX 1

TX 1

TX 2

TX 2

PIM Test Equipment

PIM

PIM Test equipment transmits 2 frequencies at high power into the system under test and measures the magnitude of the interf erence generated at the

known IM3 frequency.

The fault location is found by “tapping” on interconn ections and components (dynamic test) during the test looking f or spikes in PIM

magnitude.

PIM Severity

Metal flake

11th Order-93 dBm

9th Order7th Order

5th Order3rd Order-60 dBm

Outside PCS Rx band for

F1 & F2 selected

Repairing IM3 reduces ALL IM products.

selected

Spectrum Analyzer Mode

� IEC 62037 requires that devices be subjected

to an “impact” or “movement” while PIM

testing

� This is referred to as “Dynamic” testing

meaning “with motion”

� Loose mechanical contacts in the field may

not generate PIM until subjected to a future

environmental stress (thermal cycling, ice

PIM tests must be dynamic

FAILPASS

Poor RF Connection

environmental stress (thermal cycling, ice

loading, wind loading, etc.)

� Dynamic testing finds these intermittent

faults before they impact site performance

� PIM level must stay below the specified

maximum at all times during a dynamic test

No tapping

Tapping

Possible to have Same Band intermodulation issues

3rd order

5th order

• GSM900

935 MHz 960 MHz890 MHz 915 MHz900 GSM Rx band 900 GSM Tx Band

•

935 MHz 960 MHz890 MHz 915 MHz900 GSM Rx band 900 GSM Tx Band

• GSM1800•

5th order

7th order1805MHz 1880MHz1710MHz 1785MHz1800GSM Rx band 1800GSM Tx Band

1805MHz 1880MHz1710MHz 1785MHz1800GSM Rx band 1800GSM Tx Band

• UMTS2100

2110MHz 2170MHz1920MHz 1980MHz2100 UMTS Rx band 2100 UMTS Tx Band

•

2110MHz 2170MHz1920MHz 1980MHz2100 UMTS Rx band 2100 UMTS Tx Band

Also, Cross Band intermodulation issues involving UMTS

� DCS1800 into UMTS2100

3rd order

5th order

1805MHz 1880MHz 1920MHz 1980MHz

1800GSM Tx band UMTS2100 Rx Band

And with LTE there are multiple combinations nowada ys

Where to look for PIM on statistics?

� Main search focus on:� General – CDR, CSR, CSSR

GSM

� GSM Mean interference on Idle (IOI)� TCH Completion Rate and Drop %� TRAFFIC RATE Erlangs

� CDR data and voice � RRC Success rate% � RAB Establishment Success %

UMTS

� TRAFFIC RATE Erlangs� TCH Assignment Rate� SDCCH Assignment rate and drops� HO Success Rate� UL Quality� Erlang Minutes Per Drop� DROP_AFTER_TCH_ASSIGN� SDCCH_RADIO_FAIL

� RAB Establishment Success % � Voice Traffic Erl � PS Traffic (Mb) � Average Throughput � RTWP � RSSI

PIM test process at cell site:

Recommendations for Low PIM at site

Use only high grade products

Well Trained staff who can assemble

Use correct tooling for the

+ +

grade products <-150dBc Spc’n

who can assemble in a quality manner

tooling for the job

=

LOW PIM

KAELUS field trial evaluation

This survey was based on the sites selected by our customers to do PIM tests and where they had UL interference issues

KAELUS trials:

• >390 feeder lines surveyed.

• 26 Operators and OEMs, 17 countries

• Many PIM problems recorded

PIM Survey in EMEA by KAELUS

71.87%

28.13%

• Few VSWR problems found

The sites were originally commissioned with Sweep test equipment so it is no surprise that the VSWR results are good

2.56%

Sites or sectors withPIM problems

Sites or sectors withVSWR problems

Sites or sectors withoutPIM Problems

101

50

On sites with PIM problems, different site technology feeder lines

were tested.

PIM Survey in EMEA by KAELUS

5044

25 2413

6 6 4 2 2 2 2

GS

M90

0

GS

M90

0/G

SM

1800

/UM

TS

2100

GS

M18

00

GS

M90

0/U

MT

S21

00

UM

TS

2100

GS

M90

0/G

SM

1800

GS

M18

00/L

TE

1800

/UM

TS

2100

GS

M18

00/U

MT

S21

00

UM

TS

900

CD

MA

450

GS

M90

0/U

MT

S90

0

LTE

2600

CD

MA

850

• The PIM defects found were primarily due to workmanship issues at the RF connections.

• Many lines had multiple defects

PIM Survey in EMEA by KAELUS

64.77%

33.45%

15.30% 14.23%20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

• KPI improvements reported on the majority of sites that PIM was detected and repaired at site

14.23%

0.00%

10.00%

20.00%

Connectors Jumper Cables Other PassiveDevices

Antennas

Poor cable

preparation

Dirt / trash

Poor cable

preparation

Cable damageCable damage

External PIM Sources

KAELUS PPIM Solutions

� Summitek Instruments has been producing “bench top” PIM test systems for more than a decade

� Summitek has delivered more than 800 BPIM systems worldwide

PIM testing is not new!

systems worldwide

� These systems have been used by RF equipment manufacturers to reduce PIM in their component designs

What is relatively new is 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� Installation workmanship issues

� Component damaged during installation

� Component damaged in transit

PIM test equipment: iQA Series

� High Power – Premium

� Adjustable power (2 – 20W)

� Adjustable frequencies

� Rugged construction

� Integrated transit case

� Panel PC with touch screen interface,

on-board reporting

RTF

New USB port

Monitor port with 12VDC on center pin

32mm socket no longer required to access connector saver

RTF Module kit contents

RTF Module

Type-N cable

USB cable

iQA with RTF attached

User interface

RTF Resolution

RTF Module

Our PIM testing heritage :

� Developed factory PIM test systems for RF

Equipment manufacturers in 1996.

� >800 Factory PIM test systems in service

� Developed Portable PIM systems for

wireless operators in 2004.

� >2000 Portable PIM test systems in service

Thank you…

© 2011 Kaelus Inc. All Rights Reserved

www.kaelus.com