Passive Intermodulation Fundamentals - Livingston · What is Passive Intermodulation (PIM) ? PIM =...

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Passive Intermodulation Fundamentals

Eduardo Aires

Sales Director, EU/ME/India

� 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 Wireless Telecoms: Triasx, Summitek, Allrizon and the commercial division of TRAK Microwave Ltd.

Smiths Interconnect

AMERICAS : EMEA: APAC :

Global Technical Service & Support

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.

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

f1+f2f2-f1

2f1-f2

2f1 2f2

2f2-f13f2-2f14f2-3f1

3f1-2f24f1-3f2

InterferenceInterference

Desired

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)

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

• Multi-technology sites (GSM 900 MHz, GSM 1800 MHz, UMTS 2100 and 900 MHz, CDMA 450, ...LTE)

Combining UnitGSM 900GSM 1800WCDMA

1800/WC

900/1800

Triplexer

RF Output ports

PSPSOutdoor

AntAnt

PSPSAntAnt

AntAnt

IndoorArea 1

IndoorArea 2

IndoorArea 3

IndoorArea 4

IndoorArea 5

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.

Poor cable

preparation

Dirt / trash

Poor cable

preparation

Cable damage

Sweep testing vs. PIM testing:

Incident signals

Reflected + interference

signals

Transmitted 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)

Non-Linear Infrastructure

How to test 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 intercon nections and components (dynamic test) during the test looking f or spikes in PIM

magnitude.

PIM Source

PIM Test Equipment

Dynamic Testing:

� Fault locations are found by gently “tapping” on connections or components

� Tapping on a “bad” junction causes PIM to spike

� “Dynamic” PIM testing is very important!

� Finds the location of “static” PIM failures

� Stresses all connections to make sure that the feed system is robust and will

not fail prematurely due to environmental exposure (Hot, Cold, wind loading,

vibration, etc.)

PIM Severity

Repairing IM3 reduces ALL IM products.

Metal flake

11th Order-93 dBm

9th Order7th Order

5th Order3rd Order-60 dBm

Outside PCS Rx band for

F1 & F2 selected

Spectrum Analyzer Mode

Possible to have Same Band intermodulation issues

3rd order

5th order

7th order

• GSM900

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

• GSM1800

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

• UMTS2100

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

Also, Cross Band intermodulation issues involving UMTS

� DCS1800 into UMTS2100

1805MHz 1880MHz 1920MHz 1980MHz

1800GSM Tx band UMTS2100 Rx Band

3rd order

5th order

And with LTE there are multiple combinations nowada ys

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

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

PIM testing is not new!

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

� 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

PIM test equipment: iQA Series:

9 10 11 12

15 16 14

Time Trace Spectrum AnalyzerFrequency Sweep

Additional User Modes

iQA Series Reports:

� Build final site report as you go

� No post processing of data required

� Output finished report from the iQAin .PDF format

� Screen shot “pictures” available for engineering reports

iQA RTF

KAELUS Case Studies

GSM 900 + WCDMA 850 Indoor DAS System

GSM 900 + WCDMA 850 Indoor DAS

A carrier operating a WCDMA850 network overlaid on a GSM900 network had an in-building distributed antenna system suffering from

high Dropped Call Rates (DCR).

The DCR was logged over a period of time and plotted in. There was a significant increase when the CDMA equipment at the site was

switched on.

After all PIM generating connections were reworked the receiver noise floor was reduced to -112dBm.

Rx Noise Rx Noise floor before floor before PIM testingPIM testing

Rx Noise floor Rx Noise floor after after

reconstruction reconstruction using PIM using PIM

testertester

Here Here --a 5dB gaina 5dB gain

at the noise floorat the noise floor

This improvement allowed the receiver to provide optimum performance without interference. The increase in the number of successful calls is evident.

Held calls Held calls before PIM before PIM

testingtestingIncreased held Increased held

calls after calls after reconstruction reconstruction

using PIM testerusing PIM tester

UMTS2100 Rooftop Site

3G RooftopUrban dense site

Surge Arrestors were the source of PIMAfter their replacement

Drops in Voice and Packet improved

After PIM changes

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

www.kaelus.com

Contact Us:

Eduardo Aires

Sales Director, EU/ME/India

eduardo.aires@kaelus.com

Mob:+351 733 03 55

www.kaelus.com

Thank you…

Passive Intermodulation Fundamentals - Livingston · What is Passive Intermodulation (PIM) ? PIM =...

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