tom sullivan july 14, 2011 pim fundamentals & support

Tom Sullivan • July 14, 2011

PIM Fundamentals & Support

2PRIVATE AND CONFIDENTIAL © 2011 CommScope, Inc

Agenda – PIM Fundamentals & Support

• PIM Fundamentals (Passive Intermodulation)

• PIM Contributors & Measurements

• PIM Happens---Just Not On Our Watch Campaign

• Conclusions

• Questions & Answer Session


What, When, Where

Base Station

Antennas

TMAs, Diplexers

Cable

Filters,Amplifiers Duplexer,

Diplexers

Duplexer, Diplexers

TMA

Bias Tee

Base Station Antennas

Connectors

HELIAX™, Feeder Cable

Jumpers


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


PIM Fundamentals – 2A-B Component

• Understanding 2A-B

2A – B RX PIM = 844 MHz 3rd order

TX (F1) or A = 869 MHz

TX (F2) or B = 894 MHz

2B – A RX PIM

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


PIM Fundamentals – Contributors to PIM

• Site•Guy Wires•Steel Tower•Other Sites IMD•Lighting

• Installation•Poorly torqued connectors•Scratches•Contamination on conducting surfaces

•Contamination left in dielectric material

• Components•Poor quality of components•Poor component durability

• Materials•Hysteresis•Rust•Ferromagnetic materials•Semi-Conductive Films• Poor Quality Plating

• Test Equipment•Poor Quality Loads•Low Quality or Damaged Jumpers, Adapters, and Connectors

•Handling and usage causing deterioration

• Other•Microphonics•Welders•Contact Pressure


• 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

PIM Measurements–Field Observations

Clear sky -123 dBm (-166 dBc)

Person nearby with phone, keys, adapters, and badge -94 dBm (-137 dBc)

Pointed at fence -102 dBm (-145 dBc)

Towards forklift -84 dBm (-127 dBc)

Near shelter -102 dBm (-145 dBc)

Near cabinet and test equipment -96 dBm (-139 dBc)


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


PIM Fundamentals – dBm & dBc

-173 dBc

-163 dBc

-143 dBc-100 dBm

-130 dBm

-120 dBm

0 dBc+43 dBm

0 dBm -43 dBc

+37 dBm -6 dBc

-50 dBm -93 dBc

173 dB

PIM level is expressed in either dBm or dBc

Absolute power relative to 1mW

Power relative to the carrier levelRelative dB

20 watts

Not to scale

+40 dBm -3 dBc10 watts5 watts

2 watts +33 dBm -10 dBc


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.


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


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


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


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


PIM Fundamentals - Improperly Torqued Connections

• Hand-tightening of connectors can provide unstable and non-repeatable measurements. Use torque wrench with connector manufacturer recommended settings.

Improper TorqueTorque WrenchNote: Use 2 wrenches where necessary


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


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


PIM, A Disruptive Problem that Continues to Grow!


Support & Solutions - Campaign Theme


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


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


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.


Once a component is isolated and identified as lacking PIMcompliance 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.


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 [email protected]


PIM Fundamentals Class Links

Links to SureFlex Rapid Response

Program

1-800 Contact InfoAnd email contact

Identifies 5 legs of

program

Andrew Website Landing Page:

www.commscope.comUnder Support

Section/PIM Support

PIM Calculator

Download Marketing Collateral

Links to PIM Blogs


• 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: [email protected]


CommScope can help!

Thank you!

Questions?

tom sullivan july 14, 2011 pim fundamentals & support

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