Jay R. Maple Applications Engineer 303.378.3475
Smiths Group PLC
Global Technology Company
Listed on the London Stock Exchange
22,000 employees, Active in 50 countries
2010 sales = $5.4 Billion USD
Test Instrument Heritage Summitek Instruments: Denver, CO
Founded in 1996, Acquired by Smiths in 2001
Summitek’s primary business is manufacturing Passive
Intermodulation (PIM) test equipment
>800 Bench-top PIM systems worldwide
Triasx: Brisbane, Australia
Founded in 1995, Acquired by Smiths in 2008
Recognized leader in the design and manufacture of innovative RF filter based products
#1 PIM Test Equipment manufacturer worldwide.
Pioneered development of Portable PIM systems with Telstra in Australia in 2004
Partnership with Summitek in 2007
>1000 Portable PIM systems worldwide
What is Passive InterModulation (PIM)
PIM = Interference
PIM = Noise generated by Tx signals interacting with materials in the RF path
PIM = Reduced BTS Coverage and Capacity
What causes PIM? Anything introducing distortion within the RF path;
Loose / inconsistent metal to metal contacts Not enough contact pressure. Cracked solder joints Cold solder joints Scratches or dents at mating interfaces Burrs Metal flakes, chips, dust Improperly formed / sized parts Misaligned parts Rough mating surfaces (saw cut) Loose bolts Ferromagnetic materials (steel, nickel, etc.) Contamination Trapped between mating surfaces Trapped between plating layers Surface Oxides.
The result… MANY unwanted frequencies are generated. Desired Interference
Interference f 1
f -f 2 1
f 2
2f -f 1 2 3f -2f 1 2 4f -3f 1 2
2f -f 2 1
3rd Order 5th Order 7th Order
3f -2f 2 1 4f -3f 2 1
2f 1
f +f 1 2
2f 2
Ideal Infrastructure Minimum loss
Transmitted signals
Incident signals
Linear Infrastructure (No new frequencies)
Minimum
Reflected signals
Reflections measured by sweep test
Measures the quality of impedance matching in the system.
Return Loss:
Return Loss
Pr
PT
-3 dB
50%
50%
-6 dB
25%
75%
-9 dB
12.5%
87.5%
-12 dB
6.3%
93.7%
-15 dB
3.1%
96.9%
-18 dB
1.6%
98.4%
-21 dB
0.8%
99.2%
Return Loss is a ratio of Power Reflected to Power Transmitted
Has become the standard quality metric to measure installation quality
Non-ideal Infrastructure
Incident signals
Transmitted signals Non-Linear Infrastructure (Creates new frequencies)
Reflections still measured by sweep test Reflected + interference signals
Interference measured by PIM tester
Smiths Group PLC
Sweep test measures efficiency of signal propagation
PIM test measures ability to propagate signals without generating interference
Both tests are important and necessary to insure quality site construction.
What is new is the availability of rugged, portable versions.
Portable PIM test sets were developed in Australia at the request of Telstra by Summitek’s sister division, Triasx
Summitek / Triasx have delivered more than 1000 PPIM systems worldwide
These systems are being used by network operators worldwide to reduce PIM in their RF infrastructure
How does a PIM tester work?
PIM Test Equipment
Low PIM Load PIM Source
Transmit tones in Guard Band frequencies BTS Receive
BTS Transmit
z H M 5 4 9 1
IM3
F1
F2
Test Tone (5 KHz) Guard Band
A
D
dBm
dBc 0dBc
2 x 20 Watts +43 dBm 0dBm R E I R R A C
-100 dBm
M I P
Absolute power relative to1mW
=
-143 dBc R E I R R A C
M I P
Power relative to the carrier level
PIM level is meaningless without also stating the carrier power level 20 Watts
PIM level is VERY dependent on test power level
2 Watts +43 dBm
+33 dBm
3dB change in PIM level for every 1dB change in test power
2W not enough power to certify a site
IEC 62037 recommends 2x 20W (+43dBm) test carriers
R E I R R A C
0dB m -100 dBm
Noise Floor M I P
R E I R R A C
-130 dBm
M I P
However… 4W test sets are useful.
Light weight (11 lbs)
Battery operated
Highly portable
Able to identify loose connections
Able to find very bad components
PIM Sources at the cell site:
Site
Materials
Guy Wires
Rust
Steel Tower
Ferromagnetic materials
Other Sites IMD
Poor Quality Plating
RF In-Line Surge Arrestors
Low Grade Antennas
Poor Quality Loads
Roof Flashing/Vent Hoods
Low quality or damaged jumpers, adapters and connectors
Test Equipment
Installation
Misc.
Poorly torqued connectors
Scratches
Cracked / Cold Solder joints
Stress Fractures
Contact Pressure
Contamination • On conduction materials • Dielectric material
Relatively new 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
Components damaged during installation
Components damaged in transit
Historically, “Sweep” testing has been the only method available to measure installation quality.
A low power signal is transmitted into the system and the magnitude of the reflected signal is measured
The Tx frequency is stepped across the operating range of the site and the ratio of Reflected Power vs. Transmitted Power is displayed at each frequency
Sweep testing will identify many defects:
Kinked jumpers, crushed coax
Poorly matched components (Antennas, Filters)
Sweep testing can not identify PIM problems at a site
One frequency transmitted at a time
At very low power
Both Sweep testing and PIM testing are needed to ensure optimum cell site performance.
This is illustrated by test data collected at cell
Survey Results
sites exhibiting poor KPI’s 80.0%
>100 feed lines surveyed 19 operators, 11 countries
73.4%
70.0% 60.0% 50.0%
Many PIM problems recorded
40.0% 30.0%
Few VSWR problems found
The sites were originally commissioned with Sweep test equipment so it is no surprise that the VSWR results are good
20.0% 10.0%
5.5%
0.0% PIM proble ms
VSW R proble ms
PIM defects found:
The PIM defects found were primarily due to workmanship issues at the RF connections
Survey Results 70% 62.50% 60%
Many lines had multiple defects 50%
Other Passive Devices with PIM problems included:
41.25% 40%
30%
Diplexing filters Surge Protectors Bias-T’s
20%
17%
16.25%
Ante nn nnas
Othe r Passive Devices
10%
KPI improvements reported on the majority of sites repaired
0%
Feed Feed Cabl Cables es
Jump Jumper er Cables
How to recognize PIM problems in your network: High Dropped Call Rate
PIM induced noise shrinks the effective cell size.
Gaps in coverage result in higher dropped call rate.
Significant increase in call drops after a new carrier was added to a DAS system with PIM problems.
How to recognize PIM problems in your network: GSM: Elevat Elevated ed Interference Interference on Idle Idle (IOI) channels High interference levels before fixing PIM problems.
PIM problems corrected
Increased successful traffic channel (TCH) allocations
Decreased interference after fixing PIM problems.
How to recognize PIM problems in your network: CDMA: High Access Channel Utilization
BTS is “blind” to new mobiles trying to access the cell
Not impacting Dropped Call Rate because the call never initiated on the sector
PIM problems corrected Significant improvement after fixing PIM.
PIM Severity: 5th Order th
11 Order
9th Order
3rd Order -60 dBm
7th Order
-93 dBm
Outside PCS Rx band for F1 & F2 selected
Spectrum Analyzer Mode
Higher order products can be quite severe!
Repairing IM3 reduces ALL IM products.
Metal flake
Resistive loads generate PIM
90º connectors typically not as good as straight connectors.
RF Connector Selection:
Avoid using Type-N 7-16 DIN connectors are more robust and produce less PIM
Poor cable preparation
Dirt / trash
Poor cable preparation
Multiple PIM Sources
1
2
Largest PIM generator may mask smaller sources.
PIM displayed PIM Source #1 PIM Source #2
Multiple PIM Sources
1
2
Larger PIM source must be removed before lower level source can be seen.
PIM displayed PIM Source #1 PIM Source #2
PIM sources can be external to the system!
Incident signals
Transmitted signals Linear Infrastructure
PIM
Reflected + interference signals
If external PIM is suspected, rotate antenna on mast. PIM
PIM
45º Rotation
Elevation tilting may be more effective to identify external PIM sources.
PIM
PIM
15º Rotation
External PIM Sources
Antenna Testing Make sure there are no PIM sources within the field of view of the antenna! Recommendations:
BE SAFE!
Point antenna toward the sky
No metal objects within the half-power beam widths of the antenna in both Azimuth and Elevation
Antenna should be placed on non-metallic supports during test
Test equipment and test operators should be located off the end of the antenna; not the side
Use a “known good” antenna to verify the
test environment before testing
SKY
PIM
PIM
SKY
PIM
1dB improvement in receiver sensitivity can mean as much as 11% fewer radio base stations
Source Harri Holma and Antii Toskala, WCDMA & UTMS Nokia Finland 2004. publisher John Wiley and Son USA
Summary
PIM = reduces site performance
PIM sources can be eliminated / minimized through:
Careful construction techniques’
Use of low PIM components
Careful site design
PIM testing should be dynamic (not static)
PIM testing AND VSWR testing are needed to verify system performance
Break
PIM test equipment: iHA Series
Highly portable
Battery operated
2x 2W test tones
Fixed frequencies
Useful for component testing / fault finding
PIM test equipment: iMT Series:
High Power - Economy
2x 20W test tones
Fixed frequencies
Rugged construction
Integrated transit case
Laptop interface for reporting New iMT-850B
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
Accessory Kits:
iQA-130A – Soft Case
iQA-110A – Hard Case
Transit case
Jumper cables
Adapters
Wrench
Torque Wrench
Low PIM load
PIM source
Cleaning kit
iQA Series
Precautions
iQA Physical Characteristics
Telescoping handle
Shock mounted electronics
360º air inlet filter surrounding electronics
Fold-out legs for bench use.
Cooling fans 2 on sides 4 internal
Storage pouch Wheels
Rugged case
iQA User Interface 6
5
7
2
1
3
4
iQA Software 15
USER SCREEN
16
14
17 18
13 20 19
8
9
10
11
12
iQA Software – Additional User Modes
Time Trace
Frequency Sweep
Spectrum Analyzer
iQA Software - Reports
Build final site report as you go
No post processing of data required
Output finished report from the iQA in .PDF format
Screen shot “pictures” available for
engineering reports
iMT series
iMT Physical Characteristics
Telescoping handle
Weather resistant seal Internal Cooling fans Wheels
Rugged, integrated transit case
iMT User Interface 6
5
7
8
2 1
4 3
10
9
iMT Software Remote Terminal Application loaded on Laptop Computer.
Very similar to iQA software
Serial connection between laptop & iMT
Laptop controls iMT operation
Reports stored directly to laptop computer
iHA Series
iHA Series RF on button
• Battery Check •Display Mode
Measurement Level LEDs
Alarm LEDs
RF Output Port
RF ON indicator
Verification Procedure
Contact Us:
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