RF Channel Simulators add Hardware-inthe-Loop Test Capability to STK
Steve Williams, RT Logic
swilliams@rtlogic.com, 719-598-2801
RF Channel Simulation
 Whenever a transmitter and receiver are in motion with respect to
one another, flight and ground COMMS systems must be tested
against many conditions, both nominal and worst-case:
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Carrier and Signal Doppler
Shift
Delay
Losses
Noise
Interference
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Intentional
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Unintentional
Terrain & overhead
obscuration
Natural and man-made
atmospheric conditions
Flight paths, orbits, ground
paths, ground locations
Transmitter characteristics
Receiver characteristics
Antenna patterns
Etc…
True for: satellites, UAVs, aircraft, missiles, targets, ships, rockets, ground vehicles, ground locations, etc.
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RF Channel Simulation
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STK provides superb simulation, analysis,
reporting and visualization tools
STK provides easy-to-use scenario creation and
modification tools
STK provides a solid physics engine
Results in high confidence that
the COMMS system should
work.
At some point though,
hardware-in-the-loop
testing must occur with
the actual COMMS
systems devices.
This is not a departure
from STK, but rather a
hardware add-on to it.
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Example: Adaptive Coding and
Modulation (ACM) Modem Test
May include inband ACM control
signals
May include inband ACM control
signals
Ethernet
Ethernet
Tx
Rx
ACM Satellite
Modem (or
components)
under test
Tx
Rx
ACM Satellite
Modem (or
components)
under test
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Satellite Replaced by
Channel Simulator
Point-to-Point
Advanced COMMS
Transmitter Characteristics
Receiver Characteristics
Antenna Patterns
Interference
Losses
Etc.
STK Scenario
May include inband ACM control
signals
RF
Channel
Simulator
Ethernet
Tx
Rx
ACM Satellite
Modem (or
components)
under test
Ethernet
Tx
May include inband ACM control
signals
Rx
ACM Satellite
Modem (or
components)
under test
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STK Control of the
Channel Simulator
STK Scenario
STK
Spreadsheets
- user created
- from STK
reports
User Programs
GUI
Ethernet
Ethernet
Ethernet
Tx
Rx
ACM Satellite
Modem (or
components)
under test
Tx
Rx
ACM Satellite
Modem (or
components)
under test
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Role of the Channel Simulator
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Create or perturb RF/IF signals to
match a particular scenario.
 Fully physics-compliant
 Phase-continuous
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Delay
Especially important for phase shift keying
modulation (BPSK, QPSK, etc.)
Real-time
High-resolution interpolation
(~18.7ns)
Doppler Shift
Path Loss
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Role of the Channel Simulator
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Satellite passes are a fairly simple
channel simulator task.
A missile flying on a test range, for
example, is quite different.
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Example: Testing the Test Range
STK
Scenario
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Telemetry
Data
Space Launch Ranges
Missile & Weapons Test Ranges
Aircraft Test Ranges
Etc.
Channel
Simulator
Amplifier
Amplifier
Telemetry
Tracking Site
Equipment
Channel
Simulator
Amplifier
Amplifier
Telemetry
Tracking Site
Equipment
Range
Control
Center
BSS
Channel
Simulator
Amplifier
Amplifier
Telemetry
Tracking Site
Equipment
Displays
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Example: Testing with
On-orbit Assets
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Inter-satellite links
Aircraft / Satellite links
Satellite / Ground links
Etc.
To-be-launched
LEO Satellite
Simulated LEO-toGEO signals
On-orbit
GEO Satellite
Signal carrying response of
GEO to simulated LEO signals
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Other uses
 Almost any situation where transmitters and
receivers will be in motion
Flight
Profile
Stimulus
Signals
Transmitter
System or
Component
Under Test
RF or
IF
Channel
Simulator
RF or
IF
Receiver
System or
Component
Under Test
Received
Signals
System
Response
Analysis tools, systems and processes to
determine that Received Signals and/or System
Response was appropriate based on the
Stimulus Signals provided.
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Role of the Channel Simulator
 The Channel Simulator performs complex tasks, but must be very
easy to use.
 Keep users focused on the problems they are trying to solve, not
how to make the instrument work.
 STK Control
 Spreadsheet Control
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Can be fed by STK Reports
 GUI Control
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May contain STK elements in the future, via STK Engine
 User-program Control
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TCP/IP ASCII/Binary Commands
Synchronized to real-time events
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Channel Simulator STK9
PlugIn Implementation
Comms
Systems,
receivers,
transmitters,
sensors and
antennas may
be included.
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Summary
 STK is a advanced modeling, simulation and visualization
package based on a solid physics engine foundation.
 The Channel Simulator is a sophisticated RF instrument that
adds high-accuracy, physics-compliant carrier and signal
Doppler shift, delay, attenuation, noise and interference to test
signals for a wide variety of applications.
 Together, the combined solution is powerful, easy-to-use,
flexible, cost-effective and unique.
 For further information
– Steve Williams, RT Logic, Colorado Springs, CO.
– swilliams@rtlogic.com, 719-337-8103
– www.rtlogic.com/t400cs
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