Andrew11_JR_008 (V03)

700MHz vs. 850MHz PIM Analysis

14-January-2011

2PT-104220-ENPRIVATE AND CONFIDENTIAL© 2010 CommScope, Inc

Agenda

• Test data for antennas returned from Orlando

• Review of factory test data for 700 MHz vs. 850 MHz PIM

• PIM: Causes - Observations

• Next steps


Seven Antennas from Nsoro Warehouse in Orlando

Serial Number Port Factory 800 FLA 700 TX 800 TX 800 #2 IL 70010DESA1003893 +45 -150 -149 -169 -157

-45 -151 -133 -167 -16110DESA1003905 +45 -164 -136 -133 -168

-45 -166 -136 -154 -16310DESA1003907 +45 -174 -145 -164 -159

-45 -170 -139 -164 -14910DESA1004817 +45 -164 -135 -166 -158

-45 -168 -134 -167 -15810DESA1019390 +45 -133 -160 -163

-45 -158 -172 -15810DESA1019397 +45 -102 -152 -163 -156

-45 -122 -113 -160 -15110DESA1019398 +45 -143 -163 -164

-45 -166 -157 -166

Results over time for successive PIM testing (at Tilt=2 deg)

• DBXNH-6565B-R2M (6’, 65°, dual broadband antennas)

• Original results at factory in Mexico (800 MHz)

• Results at Nsoro warehouse in Florida (700 MHz)

• Results at Andrew facility in Texas (800 MHz) – 2 units were reworked

• Results at Andrew facility in Illinois (700 MHz)


PIM Testing 700 MHz vs. 850 MHz

• Broadband passive devices are typically not tested at every frequency of use

o Examples: cables, antennas, etc.

• Validity of this approach based on empirical test data

o Experience has shown that return loss must be good across the band

• To shed further light on field tests resulting in apparent differences between 700 MHz PIM and 850 MHz PIM, Andrew tested 157 antennas at both frequencies

• Summary data is shown on the following slides


DBXNH-6565B-VTM tested at 700, 850 MHz

• 157 antennas tested in lab environment in Suzhou, China

• Data shown includes all passes and fails

• 98% of antennas that pass 850 also pass 700.

o Variability of the test is greater than the difference between bands

• Working to further analyze the 2%


• 157 antennas tested in lab environment in Suzhou, China

• Data shown is for antennas that meet PIM specification

• Scatter plot shows high variability for both bands

• Further testing underway to better characterize the small difference between 700 and 850 MHz

DBXNH-6565B-VTM tested at 700, 850 MHz


PIM (Passive Intermodulation Distortion)

With the findings derived from extensive in-house analysis performed by Andrew’s engineering staff on the first set of seven antennas returned from Orlando, we believe the logical conclusion for the PIM readings obtained at Nsoro’s warehouse is the environment and setup in which PIM was measured.

The following three slides are submitted to reiterate the criticality of understanding the causes of PIM and the effects the environment and setup has on PIM measurements.


PIM

PIM exists at some level in all passive systems. Unlike previous technologies where careful frequency assignments could be made to avoid worst case PIM, it is not always the case with Next Generation Network (NGN) broadband signals such as LTE. Because the probability of interference is greater, the importance of a pristine test environment in measuring PIM levels is critical.

As you know, measuring for PIM is very sensitive and difficult. So much so, in fact, that Andrew believes PIM measurements are best performed within properly isolated anechoic chambers. Because this is not realistic for testing in the field, it is important to ensure the testing environment and setup are such that an accurate measurement is possible. In doing so, consideration needs be given to the causes of PIM.


PIM Causes

• 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, absorber– Improperly designed test chamber– Low quality or damaged jumpers,

adapters, and connectors– Handling and usage causing deterioration

• Other– Microphonics– Welders– Contact pressure


PIM Measurement — Some ObservationsIn addition to ensuring an adequate testing environment and setup, it is important to understand that PIM varies with the slightest interference (i.e. tapping on a connector). The measurements shown below were taken at the same site with an iQA2000 portable PIM tester.

Clear Sky –123 dBm (–166 dBc)

Towards Forklift –84 dBm (–127 dBc)

Person Nearby With Phone, Keys, Adapters, Badge –94 dBm (–137 dBc)

Near Shelter –102 dBm (–145 dBc)

Point At Fence –102 dBm (–145 dBc)

Near Cabinet And Test Equipment –96 dBm (–139 dBc)


Recommendations and Follow-On• Prior to installation, always perform antenna PIM testing on-the-ground; ensuring an

adequate testing environment and setup.

• If on-the-ground PIM testing on an antenna yields a failure, immediately contact Andrew to initiate return of the antenna.

• Upon receipt of the antenna, Andrew will assign top priority and immediately commence with root cause analysis to include retesting in a factory environment.

• If the antenna is found to be defective, Andrew will rework or replace the antenna prior to it’s return.

• If no problem is found with the antenna, the unit will be returned.

• Andrew encourages PIM training of all personnel tasked with performing PIM testing. Andrew will provide such training to include methods, causes and effects of PIM testing in a field environment.

• Andrew will provide support to audit PIM testing; as being implemented in the field by representatives of AT&T.

• Andrew has volunteered to help host validation testing of the AT&T MOP, which is currently in progress. The results of these tests will be used to provide further guidance on how to conduct field PIM testing.


Thank you!

Documents

Andrew11_JR_008 (V03)