Cosite Interference

Co-site interference analysis
Marli Strydom CST AG
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
The Cosite Scenario
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Victim Rx trying to “hear” desired signal from remote Tx
At the same time, local emitters are transmitting
Emitters can interfere with desired signal reception
= Cosite Interference
Desired Signal
Undesired Emitters
Victim Rx
THE GOAL:
predict the potential for cosite interference
for all Rx’s in the scenario.
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
The Co-Site Problem
 Multiple RF systems co-located in a common environment
 Diverse system characteristics
 Frequency bands (10 KHz to 40+ GHz)
 Power levels
 Modulation types
 Multiple EMI coupling paths
 Antenna coupling
 Cable coupling
 Circuit coupling
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Mechanisms for Cosite Interference
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There are many mechanisms for coupling
between the Tx’s and the Rx:
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Antennas
Cables
Enclosures
Conducted vs. Radiated
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Coupling can be direct between a Tx and Rx…
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Or it can be more complex…
Or even devious! (e.g., rusty bolt effect)
Non-linear interactions generate additional
spectral components (Intermodulation)
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Emitter signal spectra contain both narrowband
(NB) and broadband (BB) signal components
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Signals in-band and out-of-band must be
considered
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
The Conceptual Solution: Cosite EMI
 Many methods to achieve EMC
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Antenna placement, type
Decreased transmit power levels
Adding filters
Replacing defective hardware
Frequency planning
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Predicting Cosite EMI
The biggest challenge in making useful cosite EMI predictions lies in
managing all of the input data, models, output data, and results.
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Availability of input data – varying types and fidelities
Cosite evaluation usually cannot wait on high-fidelity system data
Data management and cosite models must allow incremental refinements
Result post-processing is critical for identifying and mitigating cosite EMI
problems.
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
EMIT
EMIT provides an approach to data management and simulation for
cosite EMI predictions.
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Inputs for an EMIT Analysis
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Antenna models
Aircraft geometry (CAD)
RF component models
Radio emissions and
susceptibility models
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Co-Site Interference Workflow
Antenna synthesis
Antenna coupling
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Co-site EMI
Predator Co-Site Analysis
GPS elliptical
patch 1.575 GHz
VHF blade
30-100 MHz
UHF blade
320 MHz
IFF2 monopole IFF1 monopole
1020-1100 MHz 1020-1100 MHz
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Broadband Multi-Port Coupling
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Installed Patterns
60 MHz
320 MHz
1.06 GHz
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
1.06 GHz
1.575 GHz
Delcross EMIT Co-Site Tool
Tx Emissions
Rx Vulnerability
Antenna Coupling
Software framework for managing
system performance data,
simulating intra-system EMI effects
and mitigating EMI issues
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Component Characteristics
Conclusion
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Emit is a system management tool
Multi-fidelity quality inputs can be used
EMI prediction can start at early level of project
As input fidelity increases, so do the EMI prediction
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Multi-Fidelity Coupling Models
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Constant Coupling - constant
Path Loss - free-space path loss
(distance)
Path Loss + Gain - computed from the
path loss and the antenna gain in the
direction between antennas.
S-Parameters - wideband coupling
from user-supplied S-parameters
(from measurements or CST STUDIO
SUITE)
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com
Fixed Value
(dB)
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Path Loss
Path Loss & Gain
S-Parameters
EMIT Library
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EMIT Library currently provides multiple models of
‘typical’ radios of interest to military and commercial
users
Each model is notated with specific details of the
system
Representative models for outboard components are
also provided
The Library content will continue to be enhanced and
updated
Users can create and maintain their own databases of
systems and components in custom libraries
Libraries can be exported for sharing with other users
CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com