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Consideration of Electromagnetic Effects in Aircraft Design

Consideration of Electromagnetic Effects in Aircraft Design . Thomas Jerse Department of Electrical and Computer Engineering Sigma Xi Brownbag Presentation 10/17/08. Electromagnetic Environmental Effects . Safety of flight Radiation Hazards Cosite interference. E 3. Who Makes the Rules?.

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Consideration of Electromagnetic Effects in Aircraft Design

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  1. Consideration of Electromagnetic Effects in Aircraft Design Thomas Jerse Department of Electrical and Computer Engineering Sigma Xi Brownbag Presentation 10/17/08

  2. Electromagnetic Environmental Effects • Safety of flight • Radiation Hazards • Cosite interference E3

  3. Who Makes the Rules? • FAA • DO-160 • JAA • Department of Defense • MIL-STD-461E • MIL-STD-464A

  4. Safety of Flight • Power Systems • Fly-by-wire controls • 3x or 4x redundancy • Air Traffic Control (ATC) radios • Navigation Systems

  5. Response to External Field AIRBORNE

  6. HIRF Testing

  7. HIRF Limits FIXED WING AIRCRAFT

  8. Response to External Field ON THE TARMAC

  9. Radiation Hazards • Personnel (RADHAZ) • Fuel (HERF) • Ordinance (HERO)

  10. Hazard to Personnel • 10 W/m2 maximum averaged over a 6 minute period • Corresponds to 61.4 Vrms/m

  11. Flight Deck Hazard

  12. E-Field Map

  13. USS Forrestal

  14. USS Forrestal

  15. USS Forrestal 162 SAILORS PERISHED

  16. Electromagnetic Environmental Effects • Safety of flight • Radiation Hazards • Cosite interference E3

  17. US AWACS

  18. Co-Site Interference Analysis

  19. A Gigantic Spreadsheet Problem • NTx = number of transmitters • NRx = number of receivers • Nb = number transceivers SINGLE-TONE ANALYSIS

  20. A Gigantic Spreadsheet Problem • NTx = number of transmitters (8) • NRx = number of receivers (16) • Nb = number transceivers (12) (548) SINGLE-TONE ANALYSIS

  21. Linear Analysis

  22. Friis Equation FAR-FIELD C = COUPLING IN dB G = ANTENNA GAIN R = SEPARATION DISTANCE l = WAVELENGTH L = CROSS-POLARIZATION LOSS POL

  23. Antennas • Antenna gain is directional EXAMPLE ANTENNA PATTERN

  24. Field from Isotropic Source

  25. Reflections SE SOURCE

  26. Diffraction and Reflection SE SOURCE

  27. Modified Friis Equation FAR-FIELD C = COUPLING IN dB G = ANTENNA GAIN R = SEPARATION DISTANCE l = WAVELENGTH L = CROSS-POLARIZATION LOSS POL SE = SHIELDING EFFECTIVENESS

  28. Nonlinear Effects • Harmonic distortion • Intermodulation distortion • Gain Compression

  29. Harmonic Distortion • All transmitters generate harmonics. • Harmonics can also be generated from a single tone applied to the receiver input circuitry.

  30. Intermodulation Distortion (IMD) • Two transmitters, one receiver Df = f1-f2 FREQUENCY Weierstrass Approximation Theorem

  31. Third-Order IMD Example

  32. Two-Tone Combinations • NTx = number of transmitters • NRx = number of receivers • Nb = number transceivers

  33. Two-Tone Combinations • NTx = number of transmitters (8) • NRx = number of receivers (16) • Nb = number transceivers (12) (5092)

  34. Re-Radiated IMD

  35. Cross Modulation • Modulation from one signal is transferred onto another MOST SEVERE ON AM SIGNALS

  36. Cosite Interference Mitigation Options • Coupling reduction • Filtering • Tuning rules • Blanking • Statistical Characterization • Active cancellation

  37. Coupling Reduction • Separation increase • Absorber • Cross polarization

  38. Filtering

  39. Active Cancellation Tx COUPLER AMPLITUDE & PHASE ADJUST + Rx

  40. Accuracy Required CONTOURS OF CANCELLATION IN dB

  41. Summary • E3 analysis is a significant portion of modern aircraft development. • Interference from both internal and external sources must be considered for safety of flight. • A thorough cosite interference analysis requires the evaluation of a large number of combinations.

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