CE101 Conducted Emissions
12 Questions to Ask Before Correcting a CE101 Non-Compliance
Engineering Perspective
A CE101 Limit Exceedance Is an Observation — Not Yet a Root Cause
CA CE101 measurement shows the current components present at the equipment power interface under a defined test configuration. By itself, however, it does not identify the mechanism that created them.
A similar exceedance may be influenced by a periodic mission load, a converter operating-mode transition, an input-filter interaction, an unintended current path or a measurement inconsistency.
Changing components before these possibilities are separated may improve the result without explaining why it changed—or whether the improvement will remain effective across the required operating envelope.
Do not begin with “Which component should we change?”
Begin with “What evidence explains the measured current?”
Notice: The numerical thresholds and calculation methods referenced in this guide reflect standard baseline specifications under MIL-STD-461G and RTCA/DO-160G Section 21. Specific defense procurement programs may impose custom tailored limit curves.
Investigation Framework
Twelve Engineering Questions Across Five Pillars
Execute this disciplined inquiry sequence before committing any layout revisions, filter restructurings, or mechanical enclosures.
01 Requirement and Configuration
02 Operating State and Load Behaviour
• Is CE101 applicable to this interface?
Verify whether contractual standards dictate low-frequency audio conducted emission limits for this specific power lead and platform category before assuming compliance failure.
• Which operating mode produced the result?
Identify whether the emission peak occurred under peak burst transmission, continuous cruise, motor stall, or nominal quiescent operation.
• Was the correct limit selected?
Confirm curve relaxation curves, platform voltage baselines, and current-draw-dependent limit offsets mandated by tailored project specifications.
• Was the input-source condition recorded?
Document DC bus voltage sag, laboratory power supply output impedance, and pre-regulator auxiliary ripple throughout measurement intervals.
• Does the test configuration represent the approved configuration?
Audit ground plane bonding, LISN inclusion or omission, cable harness length, and shield terminations against the certified test procedure.
• What does the input current look like in the time domain?
Capture oscilloscope traces of primary current to uncover pulse repetition rates, subharmonic beating, or inrush dynamics hidden by frequency-swept receivers.
03 Spectral Structure
04 Power-Network Interaction
05 Operating Corners and Evidence
• Do dominant components correspond to repeatable system timing?
Map spectral lines to known PWM clocks, motor commutation rates, or processor power-management cycles.
• Has filter–converter interaction been considered?
Check Middlebrook input filter stability criteria to verify the passive filter is not resonating against the negative resistance of downstream regulators.
• Which operating corners have been compared?
Evaluate maximum voltage, minimum temperature, and boundary load steps to confirm if the observed limit exceedance is isolated or systemic.
• Does the converter change operating mode at light load?
Evaluate pulse-skipping, burst mode, or discontinuous conduction which often introduce sub-10 kHz current harmonics.
• Are the current and return paths physically defined?
Inspect mutual loop geometry, chassis reference paths, and common-impedance coupling points along the power distribution tree.
• Does controlled A/B evidence exist?
Ensure differential measurements were performed by holding all setup parameters static while varying only one targeted operating parameter.
Electrical Topology
Interface Propagation Chain
Platform Power Source → Source Interface → Cable and Return → EMI Input Network → Converter → Mission Loads
“A CE101 result reflects the behaviour of the complete power interface—not only the EMI filter.”
PreEMC Engineering Principle
Methodological Workflow
FRAME → REPRODUCE → CORRELATE → DISCRIMINATE → VERIFY
We replace unconstrained component swapping with systematic physical parameter isolation, isolating harmonic source generation from distribution line resonance before hardware commits.
Forthcoming Analysis
Related Insights
Why Average Power Does Not Fully Explain a CE101 Result
Why Lower Power Can Produce a Different CE101 Signature
When an EMI Input Filter and a Power Converter Interact
An examination of instantaneous harmonic peak currents versus RMS power rating conventions in pulse-load systems.
How light-load converter behavior, DCM transitions, and burst modes trigger severe low-frequency conducted emissions.
Investigating negative incremental impedance instability and passive damping design to stabilize the primary interface.
Decision Support
Before the Next Design Change, Review the Evidence.
PreEMC conducts focused technical reviews of CE101 laboratory data, converter topologies, and impedance models to identify root mechanisms prior to chamber re-entry.