PIM Fundamentals & Support
Tom Sullivan • July 14, 2011
Agenda – PIM Fundamentals & Support
• PIM Fundamentals (Passive Intermodulation)
• PIM Contributors & Measurements
• PIM Happens---Just Not On Our Watch Campaign
• Conclusions
• Questions & Answer Session
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
2
What, When, Where
Base
Station
Antennas
Base Station
Antennas
TMA
Connectors
Jumpers
TMAs,
Diplexers
Cable
Filters,
Amplifiers
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
Duplexer,
Diplexers
HELIAX™,
Feeder Cable
Bias Tee
Duplexer,
Diplexers
3
What is PIM (Passive Intermodulation)?
• PIM is unwanted signals created by “nonlinearities” in the system,
these sometimes interfering with the Base Receiver
– 3rd order PIM give the highest level of interference
• In the past, careful frequency assignments could be made to avoid
worst case PIM interference
• Next Generation Network (NGN) broadband signal such as LTE,
the probability of interference is greater
• New frequency bands increase this probability of interference.
• Potential PIM Components in band can be identified based upon
frequencies in use.
For Next Generations System:
PIM is a challenging RF Path issue
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
4
PIM Fundamentals – 2A-B Component
• Understanding 2A-B
TX (F1) or A = 869 MHz
TX (F2) or B = 894 MHz
2A – B RX PIM = 844 MHz
3rd order
Low frequency side
RX 3rd order = 2 x f1 (1738) – f2 (894) = 844 MHz
RX 5th order = 3 x f1 (2607) – 2 x f2 (1788) = 819 MHz
RX 7th order = 4 x f1 (3476) – 3 x f2 (2682) = 794 MHz
RX = f2 (894) – f1 (869) = 25 MHz is carrier and IM product spacing
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
2B – A
RX PIM
5
PIM Fundamentals – Contributors to PIM
• Materials
• Site
•Hysteresis
•Guy Wires
•Rust
•Steel Tower
•Ferromagnetic materials
•Other Sites IMD
•Lighting
•Semi-Conductive Films
• Installation
• Poor Quality Plating
•Poorly torqued connectors
• Test Equipment
•Scratches
•Poor Quality Loads
•Contamination on conducting
•Low Quality or Damaged
surfaces
Jumpers, Adapters, and
Connectors
•Contamination left in dielectric
material
•Handling and usage causing
deterioration
• Components
• Other
•Poor quality of components
•Microphonics
•Poor component durability
•Welders
•Contact Pressure
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
6
PIM Measurements–Field Observations
•
On-Site Antenna Measurements with iQA2000 Portable PIM
•
•
Clear sky RF field of view required to avoid any secondary PIM sources which could
cause false PIM failures. Retest in other positions to confirm failure.
Example: HBX-6516-R2M, Typical PIM Spec -107 dBm / -150 dBc
Clear sky
-123 dBm (-166 dBc)
Towards forklift
-84 dBm (-127 dBc)
Person nearby with
phone, keys, adapters,
and badge
-94 dBm (-137 dBc)
Near shelter
-102 dBm (-145 dBc)
Pointed at fence
-102 dBm (-145 dBc)
Near cabinet and test
equipment
-96 dBm (-139 dBc)
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
7
PIM Fundamentals
• PIM is measured as a ratio of interference signal to carrier signal,
shown in:
• dBm or dBc
• Reference (carrier) power level is typically 20W (+43dBm)
• Convert from dBm to dBc by subtracting 43
• Example: Specification of -107 dBm - 43dB = -150 dBc
• Measurement uses 2 carriers, each typically 20W
• Measurements can be 2 tone or swept mode.
• Order of PIM signal – Highest Level is for 3rd Order
• Test frequencies defined mathematically – ie, 2a-b, 2a+b
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
8
PIM Fundamentals – dBm & dBc
PIM level is expressed in either dBm or dBc
20 watts
10 watts
5 watts
+43 dBm
+40 dBm
+37 dBm
0 dBc
-3 dBc
-6 dBc
2 watts
+33 dBm
-10 dBc
0 dBm
-43 dBc
173 dB
-50 dBm
Not to scale
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
Relative dB
-93 dBc
-100 dBm
-143 dBc
-120 dBm
-163 dBc
-130 dBm
-173 dBc
Absolute power
relative to 1mW
Power relative to
the carrier level
9
PIM Fundamentals – What we are trying to measure?
Let’s visualize a typical required PIM level, -150 dBc, as a mechanical
measurement, and suppose the carrier level (0 dBc) is a length of 500
miles
In voltage terms (which relates to receiver sensitivity), a level of -150
dBc is one part in about 32 million, which is 1 inch in 500 miles.
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
10
PIM Measurement - Verify Equipment
Performance
• Must first validate the test equipment
• Use of low IM of jumper cable, load and adapters
is important
• Minimize number of adapters
• Connector faces must be undamaged
• Connectors must be tight
• There should be no mechanical strain on the
connectors
• True verification of low IM requires swept
frequency equipment
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
11
PIM Measurement - Do not use old or worn
adapters
• All connections must be clean
and tight at both inner and outer
conductors
• A loose contact is an IM
generator, especially at the inner
conductor
• Minimize the number of adapters
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
12
De-burr both inner and outer conductors
X
• Burrs, ragged edges, folds etc. in either inner or outer
cause uneven contact and poor IM
• Make sure blades in prep tools are sharp
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
13
Correct Cable Preparation is Critical
• A clean, square, properly de-burred
and debris-free cable preparation is
needed for low IM performance
• Always use the correct cable
preparation tools
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
14
PIM Fundamentals - Improperly Torqued
Connections
• Hand-tightening of connectors can provide unstable and nonrepeatable measurements. Use torque wrench with connector
manufacturer recommended settings.
Note: Use 2 wrenches where necessary
Torque Wrench
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
Improper Torque
15
PIM Fundamentals – Summary
• PIM is measured as a ratio of interference signal to carrier signal,
shown in: dBm or dBc and typically 2 carriers x 20 watts per carrier.
• PIM distortion exists at some level in all passive systems.
• PIM contributions can come from the various components
• Random phase for a typical system level
• Can be calculated
• Favorable or unfavorable phase combinations
• Best Case/Worst Case
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
16
Why is PIM a HOT topic? What changed?
•
•
•
•
•
•
Frequency Overlays – 700, 800, 900, 2000 Mhz
Co-location
Higher Traffic Level & Utilization of the Network
Expanded usage of data and ever increasing data rates
In-building coverage expansion & environment
Where we were & where we are today regarding PIM
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
17
PIM, A Disruptive Problem that Continues to
Grow!
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
18
Support & Solutions - Campaign Theme
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
19
PIM is an issue for everyone, from installers to those in
purchasing and system design. The more knowledgeable each
individual is regarding the root causes and effects of PIM, the
better the chances of minimizing its effects.
We’ve created an active PIM education and awareness
program involving easy web access to:
• Technical Articles/White Papers
• PIM Expert Blogs
• Frequently Asked Questions
• Brochures
• PIM Calculator
• PIM Testing Guidelines
Located in the “PIM Support” Section on www.commscope.com
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
20
The best way to minimize the cost and problems created by PIM is
to work to prevent it during field installation.
The Andrew Institute, now offers PIM Fundamentals, a new
curriculum designed around minimizing PIM and the best practices
for site installation.
Course Outline:
• Causes of PIM
• Antenna testing
• Cable/Connector testing
• TMA testing
• Cross Band Coupler testing
• Test equipment overview
• Hands-on demos
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
21
Should unacceptable levels of PIM be detected in
the RF path, it is critical that the source(s) be
identified and located as quickly as possible using
accurate test equipment.
Andrew’s Field Engineering Services has the
experienced personnel and field experience to
provide site support to pinpoint the sources of PIM
in your network quickly and precisely. With our core
knowledge, and expanded PIM field testing
capabilities, we’ll identify the offending component
and recommend a solution.
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
22
Once a component is isolated and identified as lacking PIM
compliance or exceeding system specified PIM performance level, it
must be replaced as soon as possible.
Andrew Solutions has a dedicated PIM-qualified Rapid Response
Product Replacement Program for most components.
The Rapid Response program will initially support
delivery of SureFlex™ Premium Cable Assemblies.
Replacement parts are thoroughly tested prior to
delivery to ensure they meet the customer’s
specifications for PIM compliance.
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
23
While 24-hour help through the Andrew Technical Support Center
has always been a part of our customer service program, we have
now added technical support for issues regarding PIM.
The Andrew “Intermod Squad” consists of
technical experts experienced in troubleshooting,
diagnosing, and resolving PIM issues.
You can access their expertise either on the phone,
24/7 toll-free 1-800-255-1479, or via email at
intermodsquad@andrew.com
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
24
Andrew Website
Landing Page:
www.commscope.com
Under Support
Section/PIM Support
Identifies 5
legs of
program
1-800 Contact Info
And email contact
PIM Fundamentals
Class Links
Download
Marketing
Collateral
Links to PIM Blogs
Links to SureFlex
Rapid Response
Program
PIM Calculator
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
25
• Largest inventory of CommScope factory built PIM
jumpers in North America.
• Robust inventory of Hutton built CommScope PIM
tested jumpers with industry leading prices.
• 1-2 day turn around on Hutton built CommScope
PIM tested custom jumpers.
Contact: contractorgroup@huttoncom.com
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
26
CommScope can help!
Thank you!
Questions?
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
27
PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc
28