Mastering EMC in drones

Goals

The objectives of the training Mastering EMC in drones :

At the end of this training course, trainees will be able to design and integrate electronic modules into the vehicle, taking into account couplings and limiting the effects of various sources, including radio interference and accidental or hostile jamming.

The aim of this training course is to:

• Know how to assess the EMC environment inside and outside the vehicle


• Master a method for optimised design incorporating EMC


• Know how to identify EMC risks based on the source of external or internal interference


• Know how to choose the appropriate EMC shielding, neutralisation and filtering solutions


• Be familiar with the regulations and/or specifications in force for drones

Program

1. Introduction
• Brief overview of EMC fundamentals
• Definition of drone risks and constraints
• What do drone regulations say?
• Consideration of anti-drone techniques (Counter-UAV)
• Example of US C-UAV budget


2. Vulnerability
• Distinction between susceptibility and immunity
• Discretion (undetectability, non-compromise)
• EMC analysis strategy at the start of design
• Preliminary assessment DISTURBERS → COUPLING → VICTIM
• Identifying the characteristics of the main disturbers
• Type of operation: analogue, digital, permanent, occasional.
• Maximum output signal level
• Bandwidth (or minimum rise time) 
• Main vulnerable elements
• Type of operation (analogue, digital, permanent, occasional, etc.) 
• Minimum detection level (‘discernible threshold’) at signal input


3. Examples of typical victims
• Navigation components (GPS, Galileo, Glonass receivers, gyro/inertial unit, compass, altimeter)
• Autopilot not using external signals: inertial sensors, accelerometers
• Attitude, speed and engine rotation sensors
• 0° and battery charge status sensors
• RF input stage for remote piloting signals
• Friend/foe identification? (IFF controlled by AI)
• External reference sensors: Earth's magnetic field, satellite constellations, altimeter, barometer, etc.


4. Basic verification, self-compatibility
• Internal EMC prior to any general EMC analysis
• INTERACTION MATRIX Disruptors → Victims (Internal)
• Identification of possible incompatibilities


5. Complete extra-system EMC analysis with regard to external threats
• MAJOR IMMUNITY REQUIREMENTS
• Immunity to strong HIRF or pulsed fields (Hi-Power Ultra Wide Band)
• Risk of susceptibility to conduction, direct recharge or induction (wireless)
• Envelope of the strongest THREATS, LF ------- > 10GHz
• Strong non-repeating pulse: DES, Indirect Lightning (direct impact not taken into account)
• SUSCEPTIBILITY INDEX of victims = B-Passante / Detection threshold
• Identification of victims with the highest susceptibility
• Simple susceptibility calculations in strong fields
• Worst-case coupling assumptions: Most unfavourable polarisation, minimum out-of-band rejection, etc.
• Before adding any remedies, assessment of current status: OK / NOK
• For each NOK: necessary hardening: Δ dB / frequency range?
6. Immunity validation in real flight configuration
• Behaviour in the event of failure
• ‘Return home’ on autopilot?
• Engine shutdown and parachute?
• Self-destruction (‘dead man’ detection)?
• Consideration: simultaneous presence of internal disruptors with an external threat
• Induced effects of DES or indirect lightning during flight
• Cases of critical payload


7. Extra-system EMC analysis, radiated emissions
• Radiated emissions
• Legal or contractual constraints
• Causes of frequent failures in EMI emission tests
• Discretion (Tempest), pirate decoding of remote piloting
• Simple analysis of radiated RF emissions from the main disturbances
• Worst-case spectra of fast signals
• Spectrum of radiated fields (dBµV/m) by cards, cables, rotor motors, large IC modules
• Calculations using simple, maximalist models
• For each signal family, note ΔdB exceedance, NOK relative to the standard


8. Compilation of Hardening, Susceptibility & Emission requirements
• Envelope/cumulation of the strongest Susceptibility & Emission requirements
• Roadmap for design improvement
• Introduction to passive HF filters
• Bandwidth control
• Common mode rejection
• Shielding: last resort, if no other solution available
• Filtering of all incoming and outgoing conductors
• Integration on PCB
• Avoidance of parasitic effects: connection inductors, crosstalk, etc.
• Miniature shielding zones on PCB. Possibilities/limitations of conductive plastics
• Miniature shielded cables
• Use of filled composite structures and fairings to aid overall shielding


9. Validation during design
• Feedback from consultants during initial acceptance testing
• Equivalent testing conducted on representative models or prototypes
• Off-band susceptibility testing by injection on critical inputs
• Susceptibility thresholds by current injection on strands (BCI)
• Measurement of strand current emissions using clamps


10. Review of requirements, test setups and limitations (military or civilian)
• Existing applicable tests
• Customisations specific to drones
• Consideration of ‘cyber vulnerability’
• Intrusion detector, RF attack on remote control
• Verify that an added ‘hard’ detector is not itself susceptible to interference
• Acceptance/rejection criteria
• Specific test setups


11. Conclusion
• General summary
• Books, journals or websites