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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