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With over 20 years leading the way in handheld testing Anritsu has a well earned reputation for superior measurements in not so superior conditions. learn more about the very latest handheld testing technology.
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Tips on Mitigating External PIM Sources
PIM interference causes LTE networks to invoke higher
error protection and decrease modulation complexity,
resulting in significantly lower data throughput. Proper
workmanship in the preparation of coaxial cable has a
very large impact on PIM performance, but it is no small
chore considering that these connections are often made
at the top of a tower under adverse weather conditions.
The other challenge is to eliminate PIM sources in the
RF path occurring beyond the antenna aperture, which
has become difficult since cell sites are now deployed on
rooftops, at street level, and inside buildings. While the
non-linearities themselves are relatively similar, different
techniques must be deployed in each environment to
minimize external PIM generation.
- Rooftop Installs – Directional panel antennas with 65°
azimuth beamwidth and 5°-15° elevation beamwidth
are typically deployed. The most effective way to
minimize external PIM in rooftop applications is to
avoid metal objects within the antenna´s half-power
beamwidths by placing antennas near the edge of the
rooftop with a clear view of the sector being served.
- External PIM Sources - Reducing exposure of metallic
objects within the antenna´s half-power beamwidth
is a start, but may not eliminate all external PIM
problems. In the near field of the antenna, radiation
patterns are not fully formed. Metal objects in the
near field may couple energy more strongly than if
located in the antenna´s far field. Highly non-linear
objects, such as metal safety chains or loosely
overlapping sheet metal, should be avoided in the
antenna´s near field and especially avoided within
one wavelength of the antenna aperture.
- Indoor Installs - Most
indoor antennas are
omni-directional with very
wide elevation beamwidth
due to the antenna´s
small size, making it
virtually impossible to
avoid illuminating metal
objects. While “pointing”
the antenna away from
PIM sources is not a viable
the antennas a small
distance can be very effective. Movements as small
as 0.5 m can reduce PIM levels significantly.
- Street Level Installs – Small cell deployments often
utilize street lamps and telephone poles to provide
coverage at the street level. With an omni-directional
pattern and almost no ability to re-locate the antenna
away from external PIM sources, other techniques
must be deployed. One solution is to use quasi-omni
Though each installation type has its
own challenges, the proper mitigation
techniques can reduce external PIM and
improve site performance.
3 Keys: Interference Hunting
|If you are looking for an easier way to locate interference sources, here are three key reasons to use the MA2700A Handheld InterferenceHunter™:
- Simple – With the interference mapping feature included, an easy-to-read bar chart shows current
signal levels with lines indicating maximum and minimum levels, so inexperienced users can properly
aim the antenna to find the interference source.
- Economical – One MA2700A and several antennas is 1/3 the price of
a comparable solution. Plus, the MA2700A is antenna agnostic, creating
additional savings that can amount to thousands of dollars.
- Efficient – Locating sources of interfering signals via direction finding
and mapping means time is saved hunting for interference.
Omnidirectional or omni antennas are convenient for making over-the-air (OTA) measurements on LTE networks. Modulation quality specifications for LTE transmitters are 8% EVM or less at 64 QAM. This limit should be used when making a direct connect measurement, with the addition of a small factor for instrument contribution. For OTA measurements, a larger factor should be added to consider the signal path. As a general rule, readings under 10% are acceptable. Many modern transmitter designs, however, are much better than this; OTA readings from an ideal location can also be much better than this. A good approach is to take an OTA measurement when the base station is commissioned to establish a benchmark to maintain going forward.
Enhanced Distance-to-PIM Leads to More Accurate PIM Analysis
|An enhanced Distance-to-PIM (DTP) technology in the PIM Master™ MW82119A improves resolution by a
factor of two to make it easier to locate and eliminate PIM sources more quickly in the field. With enhanced
resolution, easy-to-read red bars clearly mark the locations of PIM sources on the analyzer display. DTP quickly
and accurately identifies the location of PIM faults inside the feed system as well as beyond the antenna to
eliminate the guesswork involved in isolating PIM sources.
A new trace overlay feature allows real-time comparison between the active DTP measurement
and a previously saved DTP trace to compare “before and after” results on a site or to
clearly show the distance between an unknown PIM source and a “PIM marker” placed
in the system.
Other enhancements include two new Trace Modes to optimize PIM vs. time
measurements. FAST Trace Mode supports dynamic PIM testing, where maximum
responsiveness is desired. LOW NOISE Trace Mode improves accuracy in low-signal
Cell Master Survives the Rigors of Seven Years on the Road
|Like most site technicians,
Ken R. must endure the elements
on a daily basis. Some days, it is
sweltering heat, other times it is
sub-zero temperatures. Driving
rainstorms can come during any
season, and then there are the hail
storms for which the Midwest is
There is another environmental
challenge that all site technicians
can relate to, as well. “Over seven
years, my Cell Master™ has been
thrown around and survived the ups
and downs of bouncing in the back
of my truck. I’ve dropped it from at least ten feet up
more than once. Despite all of this, I have never had
to send it in for any repairs,” explains Ken.
Ken maintains numerous sites throughout Kansas
and Missouri. He uses his Cell Master almost every
day to test the performance of dual band 850/1900
active antennas, tower mounted amplifiers (TMAs),
and RF radiating coaxial cabling and jumpers. The
Cell Master is invaluable when he measures Bias-T
adapters to verify return loss/VSWR, cable loss, and
“I have come to rely on my Anritsu Cell Master to get
me through the toughest situations. When I am in
extremely harsh conditions I know I can rely on
the Cell Master to locate faults that
cause equipment VSWR alarms,” said
Ken. “It is invaluable when performing
traditional line sweeps and traces
to verify return loss/VSWR and DTF
measurements, and checking Tx power
For Ken, the reliability and durability of
the Cell Master makes it his handheld
test solution of choice. Despite its
compact size and light weight, the
Cell Master is designed with a highly
durable housing that meets MIL-PRF-
28800F Class 2 requirements for shock
and vibration, and the analyzer has a
wide operating temperature range of –10 ºC to 55 ºC.
“I could not perform my every day job duties
without this test set. The instrument’s reliability and
simplicity make my life easier in the field,” said Ken.
No ability to re-locate the antenna away from
external PIM sources, other techniques must
be deployed. One solution is to use quasi-omni