38
Passive Intermodulation Fundamentals Eduardo Aires Sales Director, EU/ME/India
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 f2
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
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
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
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
TX 1
TX 2
TX 1
TX 1
TX 2
TX 2
PIM Test Equipment
PIM
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
•
935 MHz 960 MHz890 MHz 915 MHz900 GSM Rx band 900 GSM Tx Band
• GSM1800
1805MHz 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
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
5
3
4
6
7
2
1
PIM test equipment: iQA Series:
8
9 10 11 12
13
15 16 14
17
18
19
20
PIM test equipment: iQA Series:
Time Trace Spectrum AnalyzerFrequency Sweep
Additional User Modes
PIM test equipment: iQA Series:
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
iQA RTF
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
GSM 900 + WCDMA 850 Indoor DAS
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
GSM 900 + WCDMA 850 Indoor DAS
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
© 2011 Kaelus Inc. All Rights Reserved
www.kaelus.com
Contact Us:
Eduardo Aires
Sales Director, EU/ME/India
Mob:+351 733 03 55
© 2011 Kaelus Inc. All Rights Reserved
www.kaelus.com
Thank you…
