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Statistical Shielding Effectiveness – A Modal/Moment Method Approach to Characterize the Average Shielding Effectiveness over a Wide Frequency Range Including Resonances. Charles F. Bunting, Shih-Pin Yu, Zulfiqar A. Khan
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Statistical Shielding Effectiveness – A Modal/Moment Method Approach to Characterize the Average Shielding Effectiveness over a Wide Frequency Range Including Resonances Charles F. Bunting, Shih-Pin Yu, Zulfiqar A. Khan Oklahoma State University School of Electrical and Computer EngineeringStillwater OK 74078e-mail: reverb@okstate.edu(405) 744-1584 Funded under NASA Grant NCC-1-01032
Overview • Modal/MoM -treat as reverb with freq. stirring • SE vs. Frequency • Various Aperture Sizes • SE vs. surface area/volume • Various Frequencies • Future plans...
Why is this needed? Trends and bounds are defined Energy-uniformity High Frequency Multimode Well defined Aperture Polarizability Low Frequency Below first resonance ? Mid-Frequency Not quite Multimode Shielding Effectiveness Frequency
What is Modal/MoM? • Use Green’s function for a rectangular cavity for the interior cavity fields excited by the aperture • Use free-space Green’s function to determine scattered field outside • Express integral equation, equating tangential components at the aperture, and solving the matrix expression (M.D. Deshpande, “Electromagnetic Field Penetration Studies”, NASA/ CR-2000-210297, June 2000.)
What is Modal/MoM? unknown mode amplitude
What is Modal/MoM? Via equivalence the magnetic current infinite ground plane
What is Modal/MoM? Weyl expansion
What is Modal/MoM? The y-polarized incident electric field outside: The x-polarized magnetic field :
What is Modal/MoM? inside the box
What is Modal/MoM? Boundary Condition:
What is Modal/MoM? Solve for Urpq and use to express fields inside
Hx Ey Single Aperture 10 0.5 cm aperture
Single Aperture SEy Single point
Single Aperture SEy
SE vs. Frequency Varying Aperture Size – 1 aperture
SE vs. Frequency Varying Aperture Size – 2 apertures
SE vs. Frequency Varying Aperture Size – 4 apertures
SE vs. Frequency Varying Aperture Size – 2 apertures >>> Different volume!
SE vs. Frequency Varying Aperture Size – 1 aperture >>> Different volume!
SE vs. Frequency Varying Aperture Size – 4 apertures >>> Different volume!
A different approach Class of Volume: V Class of surface area: S Form a ratio (as a percentage): S/V % This Class is that of circular volume with elliptical apertures…
SE vs. S/V % Various Frequencies – 2 apertures
SE vs. S/V % Various Frequencies – 4 apertures
SE vs. S/V % Various Frequencies – A wider range of ratios in the rectangular class
SE vs. S/V % Various Frequencies – A summary…
Conclusions • Examined SE for limited frequency range • Examined numerical method/basic fields • Explored SE for various aperture configurations • Examined S/V ration > classes of SE • Future • incidence angle and polarization variation • limitations of frequency stirring • Multiple components, total fields • Probability density function ???