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Kathrein T. Wulff 07/2002
Field Measurements
Return Loss Measurements of
Kathrein Antennas
HP Network Analyzer(our reference, since commonly used at Kathrein-Werke KG)
versus
Portable Equipment
Equipment
Calibration
Accuracy
Common Problems
Charts
Antennas, narrowband sweep
Antennas, broadband sweep
Mismatch load, broadband sweep
Disclaimer
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Conclusion
Kathrein-Werke KGRosenheimPO Box 10 04 44
Phone:+ 49 (0)8031 184 - 0
Fax: +49 (0)8031 184 991
antennas.mobilcom@kathrein.dewww.kathrein.de
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Return Loss Measurements Site Installations
Field Installation is demanding on staff and equipment
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Return Loss Measurements Site Installations
What needs to be done:
Mast needs to be installed
Cabling needs to be mounted
Antennas will be installed at the mast
Final Acceptance Test needs to be performed
Qualify successful installation ofall components
Measure electrical parameters ofindividual parts
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The Measurement Equipment
Return Loss Measurements Site Installations
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Return Loss Measurements Equipment
Different measurement instruments are available at the
market to meet most customer requirements.
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Measurement equipment is exposed to a changing
environment once used in the field. High as well as
low ambient temperatures combined with high or low
humidity, dust, dirt, and improper handling are typical
with many installations.
Return Loss Measurements Equipment
What need to be considered?
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Return Loss Measurements Equipment
Portable Equipment is a very popular measurement tool
Convenient, and easy handling
Robust design
Intermediate up to high accuracy
Sometimes sensitive against high electromagnetic fields
HP 8753(XX) made by Hewlett Packard is also a very popularmeasurement tool commonly used for R&D purposes andacceptance tests on sites
Reliable instrument High accuracy
Difficult to handle on sites due to the high weight and large overalldimensions
e. g.
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Return Loss Measurements Calibration
HP Calibration
A variety of different calibration options is available
Re-calibration recommended whenever a new site will be measured
A jumper cable, if required, placed between DUT (Device Under Test, e.g.antenna) and Network Analyzer needs to be included in the calibrationprocess
An accidentally disconnected jumper cable will destroy calibration
immediately
Portable Equipment
Sometimes limited calibration options
Re-calibration recommended whenever a new site will be measured A jumper cable, if required, placed between DUT and Network Analyzer
needs to be included to the calibration process
Calibration sometimes relatively insensitive against accidentally
disconnected jumper cables 9/22Home
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Return Loss Measurements Accuracy
Portable Equipment/HP Accuracy
In general both, scalar and vector measurement systemssuffer with accuracy caused by hardware components used
inside the instruments.
Quality of the hardware components combined with internal
corrective operation procedures will determine final
accuracy of the displayed measurements.
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Return Loss Measurements Accuracy
Portable Equipment/HP Accuracy
The calibration process finally determines the overall
performance of the system used for a certain qualificationprocess (e.g. antenna measurements). Calibration needs to
be performed carefully paying attention to proper calibration
standards (short, open, 50 Ohm load).
Moreover, its mandatory to enable
the correct connector types to matchRF connections of DUT.
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Return Loss Measurements Common Problems
Portable Equipment/HP
Quite often we experienced that
installation teams do not use
appropriated calibration standards,
or do not pay attention to
calibration requirements
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Return Loss Measurements Calibration Standard
HP Calibration / Portable Equipment Calibration
Instrument calibration is the most important step to probably
setup your equipment.
We strongly recommend to regularly measure and qualify
calibration components such as short, open, and50 Ohm termination.
Always use all three calibration components throughout the
entire calibration process.
Always handle calibration sets carefully.
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Return Loss Measurements Common Problems
Portable Equipment /HP
We also experienced that jumper
cables quite often suffer with
adequate RF performance.
Kathrein-Werke KG uses special
measurement cables with
advanced return loss and
appropriated phase stability.
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Return Loss Measurements Common Problems
Summary of common measurement problems
Additional adapters:
Adding adapters to match different RF connections will impact
measurement results
Additional cabling: Adding any further jumper cables will destroy accuracy of
measurement results due to phase errors and matching
errors
Strong RF fields of other base stations:
High electromagnetic fields from other sites may impact
sensitivity of measurement equipment
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Return Loss Measurements Accuracy
Portable Equipment: Possible measurement errorsas stated in Reflectometer Measurements - Revisited, Application Note from a popular
measurement equipment manufacturer
DUT with VSWR of 1.222 (20 dB return loss) S11 maximum: (20 + 0.9151) dB = 20.915 dB (VSWR of 1.198)
S11 minimum: (20 - 0.8279) dB = 19.172 dB (VSWR of 1.247)
HP Network Analyzer: Possible measurement errorsas calculated with Agilents Uncertainty Calculator Program; referred to HP8753E; Full Two Port
Calibration; calibrated with 85032B calibration set
DUT with VSWR of 1.222 (20 dB return loss) S11 minimum: (20 + 0.52 ) dB = 20.52 dB (VSWR of 1.208)
S11 maximum: (20 - 0.49) dB = 19.51 dB (VSWR of 1.237)
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Return Loss Measurements
Portable Equipment versus HP
Comparison Measurements of Antennas
Examples
Narrow Band Sweep
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Return Loss Measurements Charts
HP Results Portable Results Delta Deviation
Marker 1: -15.653 dB -15.19 dB dB = 0.463
HP8753E Portable Equipment
Note: Different HP Network Analyzer or portable equipment might deliver test results that vary from the one displayed above.
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Return Loss Measurements
Portable Equipment versus HP
Comparison Measurements of Antennas
Examples
Broad Band Sweep
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Return Loss Measurements Charts
HP Results Portable Results Delta Deviation
Marker 1: -20.013 dB -20.26 dB dB = 0.247
Marker 2: -15.732 dB -15.24 dB dB = 0.492
HP8753E Portable Equipment
Note: Different HP Network Analyzer or portable equipment might deliver test results that vary from the one displayed above.
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Return Loss Measurements
Portable Equipment versus HP
Comparison Measurements of a
Mismatched Load
Examples
Broad Band Sweep
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-25,0
-22,5
-20,0-17,5
-15,0
-12,5
-10,0
-7,5
-5,0
-2,5
0,0
1000 1250 1500 1750 2000
M1 M2
Return Loss
Model: Serial #: 00000000Date: Time:Resolution: 130 CAL: ON(COAX)
dB
Frequency (800,0 - 2200,0 MHz)
M1: -15,29 dB @ 995,30 MHz M2: -2,21 dB @ 2004,70 MHz
Return Loss Measurements Charts
HP Results Portable Results Delta Deviation
Marker 1: -15.604 dB -15.29 dB dB = 0.314
Marker 2: -2.232 dB -2.21 dB dB = 0.022
Note: Different HP Network Analyzer or portable equipment might deliver test results that vary from the one displayed above.
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Return Loss Measurements
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Conclusion
In essence not only the measurement
equipment, but basically the calibration processwith adequate standards, and jumper cables is
finally responsible for the overall measurement
accuracy.
Installation crews need to be aware about the
sensitivity, and about proper procedures toachieve best measurement results to avoid
unnecessary confusion about system
performance.HomeHome
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