RF Absorbers Jos Westhof-Jacobs Business Development V RF Absorbers Siepel/JWJ

Transcription

1 RF Absorbers by Jos Westhof-Jacobs Business Development 1 RF Absorbers Siepel/JWJ

2 Agenda Electromagnetic Absorbers Types, characteristics Reflectivity Power handling Fire retardant properties Performance measurement & Validation 2 RF Absorbers Siepel/JWJ

3 Reason for Anechoic? To achieve a reflection-free environment 3 RF Absorbers Siepel/JWJ

4 Free Space Because of the wave impedance the near field region fields can range from predominantly magnetic to predominantly electric. RFI Fieldstrength measurements are done in the Far Field The free space impedance is 377 Ohms (120 x pi) 4 RF Absorbers Siepel/JWJ

5 How does an absorber work? The Shield = 0 Ohms Free Space = 377 Ohms => Need for matching An absorber is a broadband series impedance between free space and short circuit an absorber hanging in the air is doning everything excepted what you expect 5 RF Absorbers Siepel/JWJ

6 Siepel Absorber Portfolio Ferrite FE Pyramidal foam APM Truncated APX Hybrid HY Truncated Hybrid HYT Convoluted APC High Power AHP Wedge ADM Walkway API Multilayer AT/AH Reticulated CR/PR Weatherproof AI Narrowband ASI/APU Multilayer MI Flat P Epoxy Absorber AE 6 RF Absorbers Siepel/JWJ

7 Electromagnetic Absorbers Applications & Selection EMC Radio Antenna RCS Compact Ranges PIM Outdoor Cf. Anechoic Chamber Section 7 RF Absorbers Siepel/JWJ

8 Electromagnetic Absorbers Most used for EMC Chambers FE: Ferrite (30 MHz 1 GHz) APM: Pyramidal Foam Absorber (80 MHz >40 GHz) ADM: Microwave Wedge Absorber (80 MHz >40 GHz) HY: Hybrid = Ferrite + Pyramidal (30MHz +40 GHz) P: Flat Absorber (80 MHz +40 GHz) API: Walkway Absorber (200MHz 18 GHz) 8 RF Absorbers Siepel/JWJ

9 Electromagnetic Absorbers FE10 - Unique Ferrite Absorber solution by Siepel Tiles 100 x 100 x 6,7mm are pre-glued on metal backed galvanized sheet panel (3x3 tiles; 300x300mm), with 5 fixing holes Each panel is screwed on a horizontal metal rail system which are fixed to the vertical panel stiffeners 9 RF Absorbers Siepel/JWJ

10 Electromagnetic Absorbers Pyramidal foam absorber, 80MHz - 40GHz (and above) High tech polyurethane foam 90% open cells Numerical simulation tools Full wave methods: Microstripes CST (TLM) Asymptotic or hybrid methods: XGTD Remcom (GTD/UTD) Sophisticated carbon-based aquous solution Standard power handling capability 2 kw/m² Unique manufacturing process & quality control on carbon loading/distribution 10 RF Absorbers Siepel/JWJ

11 Electromagnetic Absorbers APM Pyramidal Foam absorbers 11 RF Absorbers Siepel/JWJ

12 Electromagnetic Absorbers APX and HYT APX = Truncated APM HYT = Truncated HY HYT+ = Truncated HY with improved performance Benefits: Space saving Less susceptible to damage Ideal on and around doors (larger clear opening) 12 RF Absorbers Siepel/JWJ

13 Electromagnetic Absorbers HY: Hybrid (Wideband EMC Absorbers) 13 RF Absorbers Siepel/JWJ

14 Electromagnetic Absorbers ADM: Wedge 80 MHz +40 GHz API: Walkway 200 MHZ 18 GHz AH/AT: Multilayer Flat 450 MHz +40 GHz ASI & API: Resonant Flat Elastomer 10% of the central frequency GHz 14 RF Absorbers Siepel/JWJ

15 Absorbers Performances Measurement 30 MHz-1 GHz Coaxial line (14m long) for S11 using VNA & Time Domain Precise reflectivity measurements on a variety of (cascaded) absorbers, influence of gaps & other imperfections 15 RF Absorbers Siepel/JWJ

16 Absorber Performances Measurement > 1GHz Measurement of S21 using VNA & Time Domain Detailed measurement of incident and reflected wave over various angles)

17 Electromagnetic Absorbers Performances acc. to incidence wave APM Absorbers keep their performances for incidence angles <45 APM66 Example: APM66, 2GHz, 50

18 Absorbers Power Handling Power handling = Maximum surfacic RF Power an absorber is able to support RF Power / Surface = Watt / m 2 or Watt / cm 2 (1 Watt/c m2 = W/m 2 ) RF Power turns into heat Max. Power is related to field: P = E 2 (V/m) / Z (377 Ohms) In practice this 377 Ohms is only theory and never met and depends on antenna characteristics, distances, modulation, harmonics, etc ) For Pulsed signals, power handling value can be increased (e.g. Short pulses/low puls repetition frequencies 18 RF Absorbers Siepel/JWJ

19 Power Handling vs. Absorbers 19 RF Absorbers Siepel/JWJ

20 Siepel tests: Testing Power Handling Continuous wave CW 5 minutes At the end of the test, the sample is cut to check for internal smolding Upon request this is done for indiviual absorbers (not included in the standard Factory acceptance Test) Only done from 5-18 GHz, for lower frequencies: very expensive, since we need kilowatts of RF power 20 RF Absorbers Siepel/JWJ

21 AHP High Power Absorber Made of honeycomb and phenolic resin Black colour Handles up to 20 kw/m2!! For Military and Satellite testing, the absorbers can be ventilated for higher powers 21 RF Absorbers Siepel/JWJ

22 Electromagnetic Absorbers Fire retardancy ISO Euroclass E NRL 8093 tests 1, 2 & 3 DIN 4102 B2 UL 94 HBF ISO LOI In-house test laboratory 22 RF Absorbers Siepel/JWJ

23 Electromagnetic Absorbers Coating Standard: aquous blue paint Commonly used hi-tech colour, available in other colours as well Optional: plastic blue paint, featuring Optimized carbon binding: no finger marks, no pollution or carbon dust, keeps the chamber clean Suitable for Class Clean Rooms (Aerospace, Chips, ) High flexibility and excellent shape memory Extreme softness: very sustainable No impact on RF performances (Paint = RF transparant) Longer lifespan (in particular for movable absorbers on the floor) Improved aestetics (brightness) Available in any colour (corporate colour, logo, ) 23 RF Absorbers Siepel/JWJ