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Problem “Resonating modes”

Resonating modes. Problem “Resonating modes”. Presented by Belarusian team. Resonating modes. Problem. Resonating modes Place a mobile phone inside a metallic container with a hole in it. Investigate under what conditions the mobile phone starts to ring after calling it. Resonating modes.

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Problem “Resonating modes”

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  1. Resonating modes Problem “Resonating modes” Presented by Belarusian team

  2. Resonating modes Problem Resonating modes Place a mobile phone inside a metallic container with a hole in it. Investigate under what conditions the mobile phone starts to ring after calling it.

  3. Resonating modes Plan of investigations: • To make clear the main principles of the mobile communications; • To make sure what the signal is, and what parameters it has. • To investigate, how the conducting metal border influences the electromagnetic wave; • To research the electromagnetic field in the boxes of some primitive shapes; • To find, on which conditions the hole lets the wave pass through. • To find the best conditions for the phone to ring.

  4. Resonating modes Frequencies and standards ν GSM 1800 1710 MHz– 1880 MHz GSM 900 890 MHz– 960MHz GSM 850 824 MHz–894 MH`z GSM 1800 1710 MHz– 1880MHz GSM 1900 1850 MHz– 1990MHz These 375 Channels are used for downlink from cell tower to cell phone t These 375 Channels are used for uplinkfrom cell phone to cell tower N = 750 ν

  5. Resonating modes How does the phone ring? Uplink Downlink The phone rings

  6. Resonating modes Signal parameters

  7. Resonating modes Amplitude, polarization & wavelength (frequency)

  8. Resonating modes Timbre

  9. Resonating modes Part 1:Electromagnetic wave reflection. Resonant Cavities.

  10. Resonating modes Electromagnetic fields at the Surface and Within a Conductor

  11. Resonating modes Experimental Unit 1:Standing wave 20 sm 0 U~ V A high frequency generator Metal screen Dipole antenna connected to a Voltmeter

  12. Resonating modes Standing wave

  13. Resonating modes Resonant cavity

  14. Resonating modes Square resonating cavity b L a

  15. Resonating modes Field distribution z E В in the normal section is vortex

  16. Resonating modes Experimental Unit 2. Square cavity

  17. Resonating modes Experiment №2 r, mm L, sm

  18. Resonating modes Cylindrical resonating cavity 1 TM oscillations: R m=0,1,2… n=1,2,3… p=0,1,2… d Lowest mode:

  19. Resonating modes Field in cylindrical cavity

  20. Resonating modes Experimental Unit 3. TM oscillations We changed height and measured the minimum length of the hole

  21. Resonating modes Cylindrical resonating cavity 2 TE oscillations: c m=0,1,2… n=1,2,3… p=1,2,3… Lowest mode: d m = 1, n = 1,p = 1 R

  22. Resonating modes Field in cylindrical cavity

  23. Resonating modes Experimental Unit 4. TE oscillations We also changed height and measured the minimum length of the hole

  24. Resonating modes r, mm Experiment №4. TE oscillations H, sm

  25. Resonating modes Part 2:Hole radiation

  26. Resonating modes The slot and currents j U~ j j E E

  27. Resonating modes Round hole j E

  28. Resonating modes Experimental Unit №5. Holes

  29. Resonating modes Experiment №5. Holes

  30. Resonating modes Part 3:Phone position

  31. Resonating modes Antenna types Cell phone antennas Whip antenna Planar antenna Is tuned to resonance → changes field distribution a lot Isn’t tuned quite to resonance

  32. Resonating modes Phone position

  33. Resonating modes Box position

  34. Resonating modes Conclusions: What should we do for the phone to ring • Find a metal box for which the resonance on specified frequency may occur; • Put the phone into the antinodeof standing electromagnetic wave; • Make a slot near the antinode. Length of the node must be equal to half wave length. It must be normal to vector E; • Place the box in such way, that the slot will be parallel with the ground and will face the cell tower;

  35. Resonating modes Summary: • The four main factors which the quality of a signal depends on are: • The box shape • The hole length and position • The phone position • The box position • We need to keep amplitude as high as possible and all other signal features unchanged for the phone to ring.

  36. Resonating modes Literature: Wikipedia: Field test mode. Wikipedia: Timing advance. Wikipedia: Received signal strength indication. Wikipedia: Time division multiple access. Wikipedia: Telecommunications link. Frequency hopping on GSM networks. CDMA vs. TDMA. Steve Punter's Southern Ontario Cell Phone Page. (http://www.arcx.com/) Jackson J.D. Classical electrodynamics Feynman's lections 6: Electrodynamics

  37. Resonating modes Thanks for your attention!

  38. Resonating modes Diffraction

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