Current EMC Research at NIST

Transcription

1 Current EMC Research at NIST Perry Wilson Electromagnetics Division National Institute of Standards and Technology B O U L D E R, C O L O R A D O 1

2 NIST Organizational Structure B O U L D E R, C O L O R A D O 2

3 Electromagnetics Division Perry Wilson, Div. Chief (Acting) RF Electronics Group Ron Ginley, GL RF Fields Group Mike Francis, GL (Acting) Magnetics Group Ron Goldfarb, GL Fundamental Microwaves Materials Properties High Frequency Devices Field Parameters and EMC Applications Antennas Wireless Systems Nano-Magnetics Bio-Magnetics Superconductivity B O U L D E R, C O L O R A D O 3

4 Field Parameters and EMC Applications Project Main Tasks Field strength calibration services (SP250) Probe development EMC facilities and test methods Interference and propagation Wireless systems EMC standards and inter-comparisons Short Courses B O U L D E R, C O L O R A D O 4

5 Probe Development at NIST B O U L D E R, C O L O R A D O 5

6 Open Area Test Site 30 m x 60 m OATS B O U L D E R, C O L O R A D O 6

7 TEM Cells B O U L D E R, C O L O R A D O 7

8 Fully Anechoic Chamber B O U L D E R, C O L O R A D O 8

9 Fully Anechoic Chamber B O U L D E R, C O L O R A D O 9

10 Cone and Ground Plane B O U L D E R, C O L O R A D O 10

11 All Weather OATS B O U L D E R, C O L O R A D O 11

12 Reverberation Chamber B O U L D E R, C O L O R A D O 12

13 Reverberation Chamber B O U L D E R, C O L O R A D O 13

14 Reverberation Chambers field uniformity low frequency limit mode density 1 mode/mhz 8πV independent paddle positions frequency stirring position stirring spatial correlations de-correlation λ/2 f v 2 3 sin( kr) ρ( r) = kr ( ) 10 6 B O U L D E R, C O L O R A D O 14

15 Reverberation Chambers antenna and test object response independent of directivity chamber Q nested chambers for shielding measurements cable shielding multiple probe calibration absorption cross section P r = use as an exposure system for bio studies E 0 λ 2 η 4π B O U L D E R, C O L O R A D O 15

16 Reverberation Chambers enhanced backscatter 2 S 11 = 2 S 21 2 B O U L D E R, C O L O R A D O 16

17 Reverberation Chambers B O U L D E R, C O L O R A D O 17

18 Reverberation Chamber B O U L D E R, C O L O R A D O 18

19 Orion Manned Orbiter SE B O U L D E R, C O L O R A D O 19

20 Current EMC Research Develop SI traceable quantum based electric field probe. Develop reverberation chamber based test methods to simulate scattering rich wireless link environments. Develop new shielding effectiveness test methods. B O U L D E R, C O L O R A D O 20

21 Quantum Based Field Probe Current techniques calibrate probes using a standard field : Calculated field in a TEM cell TEM cell geometry Input power to TEM cell Probe placement inside TEM cell Calculated field in an anechoic chamber Gain of the transmit antenna Input power to the antenna Highly dependent and sensitive to the geometry of the relative positions of the calibration probe and the standard source Accuracy order of 0.5 db Sensitivity order of 0.5 V/m B O U L D E R, C O L O R A D O 21

22 Quantum Based Field Probe A probe based on atomic RF-resonance spectroscopy has the capability to measure both very weak and very strong fields over a large range of frequencies. The feasibility of developing a technique that will allow direct SI units linked RF electric field (E-field) measurements. Uses the atomic transitions of Rydberg atoms as the RF field transducer as a means for RF field detection: No antennas used No generation of a standard field for its operation Does not depend on any geometry considerations Allows for the direct measurement of the E-field Avoids the calculation uncertainties inherent in the TEM and anechoic chamber techniques B O U L D E R, C O L O R A D O 22

23 Quantum Based Field Probe Optically excite Rydberg atoms to an RF transition Arrival of an RF photon results in radiative decay of an optical photon Detect optical photon as a means to measure RF field RF 3 2 Optical Optical 4 1 Optical Detected Photon ****Reference Gallagher**** B O U L D E R, C O L O R A D O 23

24 Detected Fluorescence ( de0) τ Ω = = τ 2h π B O U L D E R, C O L O R A D O 24

25 Current Set-up B O U L D E R, C O L O R A D O 25

26 Current Set-up LIAD of Sodium Demonstrated at NIST, Boulder Blue LIAD excitation light at 455nm Sodium cell Laser beam tuned to D2 Sodium transition near 589nm B O U L D E R, C O L O R A D O 26

27 Quantum Based Field Probe B O U L D E R, C O L O R A D O 27

28 Fiber Core Probe Fill hollow core PBG fiber with Sodium gas. Small size~100um does not perturb microwave field. Microwave field is uniform inside the fiber. Deliver pump light via fiber optics. Means for efficiently collecting much (80%) of the 815nm fluoresces since atoms are inside the fiber. B O U L D E R, C O L O R A D O 28

29 Scattering Rich Wireless Links Oil Refinery Office Corridor Apartment Building Subterranean Tunnels B O U L D E R, C O L O R A D O 29

30 Reverberation Chamber Seek to simulate Rician K-factor over a large range: k = direct power/scattered power. K-factor is affected by: Absorber (Q of the chamber) Types of antennas (directive, omni) Position orientation of the antennas Replicate measured power delay profiles (PDP) Standards measurements: TRP and TIS B O U L D E R, C O L O R A D O 30

31 Example: Stamping Factory B O U L D E R, C O L O R A D O 31

32 Example: Stamping Factory Measurements at engine stamping plant reverb chamber Power Delay Profile (db) o delay-spread=277ns * mean-delay=290.5ns o delay-spread=122ns * mean-delay=130.1ns o delay-spread= 67ns * mean-delay=71.2ns o delay-spread=168ns * mean-delay=137.8ns o delay-spread=175ns * mean-delay=142.7ns o delay-spread=128ns * mean-delay=105.8ns o delay-spread=173ns * mean-delay=176.1ns 1 absorber 3 absorbers 7 absorbers flint metal, drg-drg, 10m flint metal, drg-drg, 50m flint metal, drg-drg, 80m flint metal, drg-drg, 110Bm stamping plant time (ns) Reverb chamber bounds measurement B O U L D E R, C O L O R A D O 32

33 Antenna Effect Power Delay Profile (db) Mean Power Delay Profile (100 steps) Horns Horn Indirect 1, Absorber A Horn Indirect 2, Absorber A Horn Indirect 1, Absorber B Horn Indirect 2, Absorber B Horn Indirect 1, Absorber C Horn Indirect 2, Absorber C Horn Direct CoPol, Absorber B Horn Direct XPol, Absorber B Power Delay Profile (db) Mean Power Delay Profile (100 steps) Omnis Horn Indirect 1, Absorber A Horn Indirect 2, Absorber A Horn Indirect 1, Absorber B Horn Indirect 2, Absorber B Horn Indirect 1, Absorber C Horn Indirect 2, Absorber C Omni Direct CoPol, Absorber B Omni Direct XPol, Absorber B Delay (ns) Delay (ns) Different antenna types can impact PDP B O U L D E R, C O L O R A D O 33

34 Realistic PDPs Measurements made in Denver urban canyon last summer Channel characterization and PASS device measurements B O U L D E R, C O L O R A D O 34

35 Simulating Realistic PDPs Pulse generator used to amplitude modulate RF, creates short-duration pulse Fading simulator replicates delayed, scaled versions Reverb chamber introduces exponential profile B O U L D E R, C O L O R A D O 35

36 Simulating Realistic PDPs Using multiple, overlapping pulses, we can create many difficult PDPs fitted simulated data measured Data Denver PDP [db] Delay [ns] B O U L D E R, C O L O R A D O 36

37 Shielding Effectiveness: Nested Chambers Sample B O U L D E R, C O L O R A D O 37

38 Enclosure Shielding Effectiveness IEEE 299 Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures: Physically large, electrically large enclosures Physically small, eclectically large enclosures Physically small, electrically small enclosures Problem with physically small enclosures: may not accommodate paddle, large antenna. B O U L D E R, C O L O R A D O 38

39 Small Enclosure SE From Hill we have for a planar interface (chamber wall away from edges, corners): E t ( x,0, z) = y 2 E B O U L D E R, C O L O R A D O 39

40 Small Enclosure SE Thus a small monopole and frequency stirring can be used to measure a field related to the center of the enclosure. B O U L D E R, C O L O R A D O 40

41 SE Comparison port 2 port 3 port 2 port 1 port 1 port 4 Mode-Stirred with a Horn Antenna: SE => S 31 port 2 port 1 port 3 Mode-Stirred with a Monopole Antenna: SE => S 41 port 2 port 1 Frequency Stirring with a Horn Antenna: SE => S 31 port 4 Frequency Stirring with a Monopole Antenna: SE => S 41 B O U L D E R, C O L O R A D O 41

42 SE Comparison (a) open aperture (b) half-filled aperture (c) narrow slot aperture (d) generic aperture B O U L D E R, C O L O R A D O 42

43 SE Comparison (a) open aperture (b) half-filled aperture SE (db) mode_stirring_horn 6 freq_stirring_horn 4 mode_stirring_monopole 2 freq_stirring_monopole Frequency (MHz) (c) narrow slot aperture (d) generic aperture B O U L D E R, C O L O R A D O 43

44 Aircraft SE B O U L D E R, C O L O R A D O 44

45 Space Shuttle Endeavour SE B O U L D E R, C O L O R A D O 45