Aerospace & Defense Technology - December 2023 - 26

RF & Microwave Technology
1. Elimination of coax cable insertion
loss and phase instability
2. Complete vector S-parameter
characterization possible
3. No different transmission media
(E/O, O/E) required, eliminating
additional costly hardware to
overcome coax cable issues
4. Full wide band frequency sweep
coverage
5. Easier and faster setups for more
efficient testing
Table 1: Advantages of using modular VNA with
portable ports
erably different than a traditional VNA
configuration, which requires additional
test cables and connections that can create
measurement uncertainty. Benefits
of the modular portable port approach
are shown in Table 1.
Eliminating EMI
With so much cabling and wireless
equipment aboard large vehicles, electromagnetic
interference (EMI) is a critical
factor that must be considered, as well.
EMI can cause equipment performance to
degrade or even malfunction. Radios and
radar signals are affected, as communications
between the aircraft, ship, and command
and control centers can be lost.
As a result, EMI effects must be considered
in all aspects of systems utilizing RF
cables. Standards such as RTCA DO-160
for environmental conditions and test
procedures for airborne equipment or
MIL-STD-461, developed by the Department
of Defense (DoD) to control EMI
issues, are often used as the basis of evaluation.
One
key approach to prevent EMI is to
provide shielding of various line replaceable
units (LRUs) and harnesses. Shielding
a device or system not only reduces
EMI emissions, it improves susceptibility
performance. With advances in wireless
technology and increased device signal
sensitivity, shielding becomes even more
important to maintain the functionality
and safety of equipment.
Benefits of Over-the-Air Testing
Engineers often use VNAs to test RF/
µW shielding and propagation on large
vehicles, as well. Typically, the configuration
requires very long test port cables.
At the distances required for these tests,
coax cables introduce insertion loss and
phase instability so significant that different
transmission media, such as optical
cabling, must be used to enable accurate
S-parameter measurements. The
additional hardware and setup complexity
significantly increases the cost and
time required to make the propagation
and shielding measurements.
A modular chassis-less 2-port VNA
with portable ports (figure 2) alleviates
the additional expense and improves test
times. Over-the-air (OTA) measurements
on large vehicles can be more effectively
conducted.
A VNA with modular, portable port
design is well suited to perform measurements
on wireless systems used on aircraft
and warships. Its design allows for
tests to be made using port modules up
to 100 meters apart.
Conclusion
Wireless technology is a critical element
of the modern battlefield, making
accurate and consistent transmissions
of high-speed data essential for mission
success. Ensuring wireless system performance
has additional challenges when
implemented on warships and aircraft.
A VNA architecture that allows test ports
to be connected directly to each end of
long cables in large vehicles optimizes
dynamic range and improves phase
stability in vector S-parameter testing,
for greater confidence in system performance
in mission-critical applications.
This article was written by Pete Alexander,
Business Development Manager
at Anritsu Company. For more information,
visit www.anritsu.com.
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26
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Aerospace & Defense Technology, December 2023
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Aerospace & Defense Technology - December 2023

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