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Qian Xu Project 139: Developing Eco-friendly Radio Absorbing Materials (RAM) for Anechoic Chambers

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Presentation on theme: "Qian Xu Project 139: Developing Eco-friendly Radio Absorbing Materials (RAM) for Anechoic Chambers"— Presentation transcript:

1 Qian Xu Project 139: Developing Eco-friendly Radio Absorbing Materials (RAM) for Anechoic Chambers

2 Qian Xu, 2 Outline Background Information Research Questions Systematic Solutions

3 Qian Xu, 3 Background Information Pictures from: ETS LINDGREN Micro-level Macro-level How to design the chamber ? Pictures from: RAM Type? RAM Thickness? Field Uniformity? Chamber Shape? RAM Arrangement?

4 Qian Xu, 4 William H. Emerson, IEEE Trans. on Antenn. And Propag., Vol. AP- 21, No. 4, July, Mid 1930s: Theoretical and experimental work. 1936: First patented absorber. WWII( ): Germany: Schornsteinfeger(Wesch material & Jauman absorber ), US: HARP(Halpern- anti-radar-paint) by Halpern at MIT Radiation Laboratory, Salisbury screen : Broad-band absorber. The early 1950s: First dark rooms. The late 1950s: New generation of broad-band. absorbers(-40dB normal), antenna pattern comparison method, new chamber shape, shielded anechoic chambers. 1960s: Low frequency absorber(-40dB 100MHz), 3 rd generation RAM (-60dB normal), improved absorber measurement(Free-space VSWR), tapered chamber by Emerson.

5 Qian Xu, 5 S. M. J. Razavi, M. Khalaj-Amirhosseini, and A. Cheldavi, PIER B, Vol. 19, , 2010.

6 Qian Xu, 6 Outline Background Information Research Questions Systematic Solutions

7 Qian Xu, 7 Research Questions Pictures from: 1. How to choose/analyse/optimise RAM? Ferrite tiles HybridPyramid

8 Qian Xu, 8 Research Questions Picture from: chamber.html 2. How to design/analyse/optimise the whole chamber? Picture from: 100-million-test-chamber-droid-eris-and- blackberry-bold-9700-suffer-the-same/ Tapered Chamber Aircraft Chamber Compact Chamber Picture from: compact-range/

9 Qian Xu, 9 Outline Background Information Research Questions Systematic Solutions

10 Qian Xu, 10 Systematic Solutions: Macro-level Key problem: Whole chamber design Commercial Software: CST (FEM, FITD), HFSS (FEM), Feko (MoM) Friendly GUI, General simulation software, Pricy, High performance computers(cluster), Time consuming Trial and error/cut and try Ray Tracing Full wave simulation Accuracy

11 Qian Xu, 11 Trial and error Empirically based, mostly determined by lower frequency limit. Thickness~Reflectivity Extraneous energy level~Reflectivity (Free Space VSWR Method ) Picture from: Electromagnetic Anechoic Chambers A Fundamental Design and Specification Guide, Leland H. Hemming, Chapter W=1/2L

12 Qian Xu, 12 Free Space VSWR Method Repeated again for horizontal and vertical polarisation.

13 Qian Xu, 13 Free Space VSWR Method If a 0.3dB ripple is observed 20dB down from the peak, the extraneous signal level is -55dB Ripple: Extraneous signal :

14 Qian Xu, 14 Full Wave Method Algorithm limit Consider lossy(inhomogeneous) material FEM, FDTD, GO FrequencyElectrical Size /Physical Size Electrical Volume 10MHz0.5λ/15m0.125λ 3 100MHz5λ/15m125λ 3 1GHz50λ/15m125E3λ 3 10GHz500λ/15m125E6λ 3 40GHz2000λ/15m8E9λ 3 N 3 MoM N 2 FEM N 1.1~1.2 FDTD N*log(N) MLFMM N PO/SBR/GO

15 Qian Xu, 15 Ray Tracing/GO(Geometric Optics) High frequency approximation T=R+G+P(dB) normalized to direct ray in dB T=Total strength R=reflection coefficient G=Antenna pattern gain P=Propagation parameter Ref: Electromagnetic Wave Theory, J. A. Kong, p.722. Ref: Electromagnetic Anechoic Chambers A Fundamental Design and Specification Guide, Leland H. Hemming, Chapter st order 2 nd order

16 Qian Xu, 16 Ray Tracing/GO Workflow Mesh Generation, Material/Boundary Assignment Ray Tracing Code Field Distribution Performance & Cost Preprocessing: Modeling (.stl) GND, side-wall, back-wall…. different area with different reflectivity GPU, Parallel 1 st order, 2 nd order, 3 rd order reflection (Propagation direction, Amplitude, Phase) Modified rectangular, Compact Range, Tapered

17 Qian Xu, 17 Expected Results Performance Field uniformity (±?dB) Cost Debug/Optimize 1 st order, 2 nd order, 3 rd order reflection can be used to find the source of extraneous signal. Ref: Minimum usage of ferrite tiles in anechoic chambers, S. M. J. Razavi, M. Khalaj-Amirhosseini, and A. Cheldavi. PIER B, Vol. 19, , 2010.

18 Thank you!


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