Aerospace & Defense Technology - September 2022 - 37

RF & Microwave Technology
When NTN equipment becomes
available, you should prototype this
with real equipment in the lab or chamber
on a small-scale basis. Follow that
step with a full-scale implementation,
deploying with actual equipment on
the target platform. Then, engage in
periodic maintenance testing.
2. 5G via Air, Land, or Sea
Outfitted with 5G for long-haul communications,
aircraft, ships, Humvees,
and other vehicles can use 5G to enable
communications, high-data-rate video
conferencing, and Internet of Things
sensors. Eventually, these capabilities
will evolve into self-driving or autonomous
vehicles.
Ships, planes, and ground vehicles
have different transmitters and receivers,
including telemetry devices, communications
transceivers, radar and satellite communications,
and surveillance systems.
They must all operate simultaneously
without compromising the performance
of other systems or damaging them. If
not designed properly, for example,
high-powered radar could damage sensitive
satellite receivers. Planes, ships, and
other vehicles with 5G also add complexity
to the RF environment (Figure 2).
Vehicles with communications equipment,
radar, surveillance systems, and
other equipment pose potential electromagnetic
compatibility issues. Careful
planning must take place so that all systems
can operate simultaneously and
safely. Software modeling can help you
discover potential issues by modeling
the following: the UE's downlink and
uplink transmit and receive chains, the
gNodeB, and the signal propagations of
other vehicle communications systems.
In the planning phase, simulating signals
in software determines electromagnetic
compatibility using a 3D model of
the deployment platform. The finite-difference
time-domain (FDTD) method is
based on volumetric sampling of the
electric and magnetic fields throughout
the complete space. This method
updates the field values while stepping
through time, following the electromagnetic
waves propagating throughout
the structure. As a result, a single
FDTD simulation can provide data over
an ultra-wide frequency range.
To increase confidence, you can prototype
signals in the lab on a small scale to
gauge performance in the field. Use hardware
emulators in place of COTS equipment,
as they are easy to customize and
adapt. The prototyping is conducted in a
lab or chamber on a small-scale basis.
Once you are satisfied, follow up with fullscale
implementation, deploying with
actual equipment on the target platform.
Follow with periodic maintenance testing.
In the prototype phase, simulate signals
with signal generators and other
emulation equipment. You can adjust signal
levels to simulate the real-world environment,
but on a much smaller scale
inside a chamber. The measurements
determine electromagnetic compatibility.
3. Coexistence: The Battle for Priority
For radar and satellite applications specifically,
5G raises another challenge:
coexistence. Because these applications
may use the same spectrum as 5G, they
can impact one another, leading to service
disruption or performance degradation.
Coexisting signals have the right to operate
in the same frequency range, but one
signal usually takes priority. For example,
radar signals typically take priority over
5G signals. As a result, 5G needs to shut
off or move to another frequency.
Satellite signals can also coexist with 5G
signals. For example, 5G NR FR2 overlaps
with fixed-satellite services (FSS) Earth station
uplinks at 27.5 to 29.5 GHz and FSS
downlinks at 37.5 to 40.0 GHz. This overlap
creates questions around how interfering
waveforms interact and how much
in-band and out-of-band suppression is
needed. You also need to determine how
much guard band is necessary and what
metrics to consider in assessing impact.
To test the impact of radar or satellite
on a 5G network, you can use a 5G test
UE in the field. This approach provides
a detailed view of the quality and
throughput metrics of the 5G network.
To test the impact of 5G on a coexisting
signal, you can use a signal analyzer to
measure many signal types including
radar, satellite, and 5G.
You can simulate radar signals in several
ways, depending on the fidelity and
emitter parameters required. By leveraging
software, you can generate single
radar emitters or high-density emitter
environments. These simulations create
UE emulator
RF
Bits
UEE
Core network
and
gNodeB
under test
traffic emulator
UEE wraparound
(NSA/SA core emulation)
Figure 1. Test a UE by emulating the gNodeB - the system that communicates with it. Focus on metrics
including UE battery life, battery aging, or battery life against temperature. Also, observe quality of
service like block error rate or sensitivity.
Planning
Prototype
Software
modeling
Use software to
model transmitters
and location on
the ship
Small-scale
implementation
Prototype
transceiver on a
Small scale in a
chamber and test
Deploy
Full-scale
implementation
Deploy actual
equipment on
target paltform
and test
Maintenance
Periodic
test
Pre-mission and
periodic test of
systems
Figure 2. To develop 5G systems on vehicles, use a crawl-walk-run approach beginning with basic
software modeling. The tool should model the UE downlink and uplink transmit and receive chains, the
gNodeB, and the signal propagation of other communications systems on the vehicle.
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