Passive Intermodulation (PIM), an interference challenge for the - - PowerPoint PPT Presentation

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 networks access networks access networks access 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 the multiple Tx signals and passive non-linear junctions in the RF path.

f1 f2 2f1-f2 2f2-f1 3f2-2f1 3f1-2f

2

Interference Interference Desired Increasing the received Noise floor thus reducing base station sites coverage and capacity.

f1+f

2

f2-f1 2f1 2f2 3f2-2f1 4f2-3f

1

3f1-2f

2

4f1-3f2

PIM generated products will affect received band (UL) by

PIM is getting more complex with

Networks evolution towards:

• Indoor or outdoor complex DAS

systems (shared by several

• perators)

Load 1800/WCDMA 900/1800 Triplexer

RF Output ports

PS PS PS PS PS PS PS PS Outdoor area Ant Ant Ant Ant Ant Ant PS PS Ant Ant Ant Ant Ant PS PS PS PS Ant Ant PS PS Ant Ant Ant Ant Ant Ant PS PS Ant Ant PS PS Ant Ant PS PS Ant Ant PS PS Ant Ant Indoor Area 1 Indoor Area 2 Indoor Area 3 Indoor Area 4 Indoor Area 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 Unit

GSM 900 GSM 1800 WCDMA

OP 1 BTS OP 2 BTS OP 3 BTS OP 1 BTS OP 2 BTS OP 3 BTS OP 1 Node B OP 2 Node B OP 3 Node 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 does not identify these problems.

Sweep testing vs. PIM testing:

Incident signals Transmitted signals

Non-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

PI M TX 1 TX 2 TX 1 TX 1 TX 2 TX 2

PIM Test Equipment

PI M

PIM Test equipment transmits 2 frequencies at high power into the system under test and measures the magnitude of the interference generated at the known IM3 frequency. The fault location is found by “tapping” on interconnections and components (dynamic test) during the test looking for spikes in PIM magnitude.

PIM Severity

Metal flake

11th Order

• 93 dBm

9th Order 7th Order 5th Order 3rd 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 FAIL PASS

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 MHz 890 MHz 915 MHz 900 GSM Rx band 900 GSM Tx Band

• 935 MHz

960 MHz 890 MHz 915 MHz 900 GSM Rx band 900 GSM Tx Band

• GSM1800
• 5th order

7th order

1805MHz 1880MHz 1710MHz 1785MHz 1800GSM Rx band 1800GSM Tx Band 1805MHz 1880MHz 1710MHz 1785MHz 1800GSM Rx band 1800GSM Tx Band

• UMTS2100

2110MHz 2170MHz 1920MHz 1980MHz 2100 UMTS Rx band 2100 UMTS Tx Band

• 2110MHz

2170MHz 1920MHz 1980MHz 2100 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 nowadays

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 with PIM problems Sites or sectors with VSWR problems Sites or sectors without PIM Problems

101 50

On sites with PIM problems, different site technology feeder lines were tested.

PIM Survey in EMEA by KAELUS

50 44 25 24 13 6 6 4 2 2 2 2 GSM900 GSM900/GSM1800/UMTS2100 GSM1800 GSM900/UMTS2100 UMTS2100 GSM900/GSM1800 GSM1800/LTE1800/UMTS2100 GSM1800/UMTS2100 UMTS900 CDMA450 GSM900/UMTS900 LTE2600 CDMA850

• 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
• n the majority of sites that

PIM was detected and repaired at site

14.23%

0.00% 10.00% 20.00%

Connectors Jumper Cables Other Passive Devices Antennas

Poor cable preparation Dirt / trash

Poor cable preparation

Cable damage Cable 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,
• n-board reporting

RTF

RTF Module kit contents

!"# "$%& &

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…

'()*+,!!