View
1
Download
0
Category
Preview:
Citation preview
2/12/20
1
Electromagnetic CompatibilitySpace System Design, MAE 342, Princeton University
Robert Stengel
Copyright 2016 by Robert Stengel. All rights reserved. For educational use only.http://www.princeton.edu/~stengel/MAE342.html 1
§ Problems, Analysis, and Testing§ Specifications§ Fundamentals§ Systems Approach§ Categories§ Spacecraft Charging§ Electrostatic Discharge§ Grounding Schemes§ Special Problems of Small Satellites
1
Electromagnetic Compatibility Goals
• No interference between systems or components
• Systems not susceptible to E/M emissions from any source
• No internal interference within a system• Examples of incompatibility– Static, buzzes, clicks– Electrostatic discharge– Components with different grounding
2
2
2/12/20
2
EMC Specifications• Enumerated in standards and mission-
specific documents– MIL-STD (US military)– CE (Conformité Européene)
• Various levels of requirements• Details of verification– Inspection– Analysis
• System design guidelines• Limitations imposed by specialized payloads
3
3
Terms and Definitions
• EMC• EMI• RFI• ESD• EMP
4
4
2/12/20
3
Fundamental Compatibility Issues• Source of emissions• Receiver of emissions• Transfer or coupling that facilitates
interference• Possible fixes– Reduce emissions– Alter the coupling path– Make the receiver less susceptible– Error-correction coding
5
5
Systems Approach to EMC• Top-down (performance-driven) approach• Safety margins and budgets
– Level of emissions– Definition of “worst case” limits
6GWEC, 2001
6
2/12/20
4
Categories of EMC
7
Fortescue
RF3KHz-3000GHz
picoTeslas picoTeslas0.05-100KHz
Susceptibility: Emissions picked up by harness or cables
7
Categories of EMC
8
Fortescue
8
2/12/20
5
External Sources:Magnetosphere and Van Allen Belts
Trapped Energetic Ions and ElectronsLight ions form base population of the magnetosphere
9
9
Earth’s Magnetosphere
10
Fortescue, et al, 2011
Earth’s Dipolar Magnetic Field
B Re,λ( ) = 1+ sin2 λ( )1/2B0
Re3
B0 = 0.3 Gauss
10
2/12/20
6
Integral Electron Flux Contours at Earth, Jupiter, and Saturn
11
NASA-HDBK-4002A, 2011
11
High-Energy Proton Flux in Inner Van Allen Belt
12
12
2/12/20
7
Spacecraft Charging Hazard Zones
13
NASA-HDBK-4002A, 2011
13
Spacecraft Charging
14
Interaction of sunlight, space plasma, and spacecraft materials and electronics
NASA-HDBK-4002A, 2011
Exterior Interior
14
2/12/20
8
Spacecraft Charging Damage
15
Interaction of space plasma and spacecraft materials and electronics
NASA-HDBK-4002A, 2011
SCATHA Satellite, 1979
15
Proton and Electron Penetration in Aluminum
16
16
2/12/20
9
Acceptable Surface
Materials
17
17
Unacceptable Surface
Materials18
18
2/12/20
10
Differential Solar Charging and Modeling
19
Herr, NASA
Holbert, 2006
FEM
19
Conducted Emissions/Susceptibility:Differential Mode and Common Mode
Interference Probing
20
Fortescue
1
0
(to ground)
20
2/12/20
11
Electrostatic Discharge (ESD)
• Always a “spark”• Radiated effect– RF signal due to distant pulse– Testing for radiated emissions from ESD
• Conducted effect– Discharge picked up by conducting element of the
spacecraft– Possibility of high current
21
21
Protection Against ESD• Location of components• Grounding• Bonding (~soldering)• Isolation (“Faraday cage”, “mu metal”)• Power supply to components
– Direct– Regulated– Converted
• High-impedance semiconductors (e.g., MOS)• Less sensitive components (e.g., vacuum
tubes!)• Procedures in preparation of spacecraft
22
22
2/12/20
12
Spacecraft Grounding• Reference point– 0V, earth, common, ground, chassis
• Current between “grounded” components may not be zero– Small potential between end points– Resistance and inductance of wire
• Minimize signal “cross talk” or power supply voltage differences
• Grounding techniques
23
23
Single-Point Grounding
24Fortescue
24
2/12/20
13
Multi-Point Grounding
25
Fortescue
25
Hybrid Grounding
26
Fortescue
26
2/12/20
14
Major Causes of EMC Problems:Power Supplies
27
• Switch mode power converters• Transistor operating speed• Switched voltage and current levels• Stray capacitance• Copper foil shields• Diodes
27
Major Causes of EMC Problems:DC Motors and Actuators
28
• Inductive nature• PWM• Rise/fall times• Avoidance techniques
28
2/12/20
15
Major Causes of EMC Problems:Harnesses and Cables
• Passive, yet major source of interference• Grounding and bonding• Matched drivers, transmitters, and cables• Slow down rise and fall times• Screened or twisted cables• Filtering at connectors• Impedance matching
29
29
Analysis Methods• Example: PSpice
30
• Example: MATLAB: various books and EMPLab
30
2/12/20
16
EMC Testing
31
https://en.wikipedia.org/wiki/Electromagnetic_compatibility
• Open-air test sites• Anechoic and reverberation test chambers• Spectrum analysis• High-powered pulse or signal generator
31
Small Satellite Design Philosophy
32
Fortescue
32
2/12/20
17
33
Fortescue
Small Satellite System Design
33
Use of Commercial-Off-the-Shelf (COTS) Technology
34Fortescue
34
2/12/20
18
Effects of Ionizing Radiationon COTS Components
35
• Total dose effects• Single-event
upsets/latchup
• Regular “washing” of memory
• Spot shielding• Radiation hardening
after Fortescue
35
Case Study: StangSat Testing• Project at NASA KSC• EM conduction and radiation testing:
MIL-STD-461F, RE102 Limits
36See Lecture 19 Course Materials on
Blackboard
36
2/12/20
19
Next Time:Spacecraft Mechanisms
37
37
Recommended