1. Doc.: IEEE /1006r0
July 2006
July 2006
Supporting information for eliminating Section 5.7 "OTA Shielded Enclosure Environment"
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Dr. Michael D. Foegelle, ETS-Lindgren
Dr. Michael D. Foegelle, ETS-Lindgren

2. Doc.: IEEE /1006r0
July 2006
July 2006
Abstract
This presentation illustrates the problem with using an unqualified shielded room as an environment for OTA testing. It is provided as supporting evidence for comment 240 in document 11-06/0872r1.
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Dr. Michael D. Foegelle, ETS-Lindgren
Dr. Michael D. Foegelle, ETS-Lindgren

3. Shielded Rooms Comment on section 5.7:
July 2006
Shielded Rooms
Comment on section 5.7:
A pure shielded environment does not give an RF channel suitable for OTA testing. A shielded room is intended to isolate devices/systems within the room from the outside environment, either to protect those devices from outside interference, or to protect the environment outside from interference due to the tests performed in the shield. It is NOT intended for testing of OTA propagation. There will be far too much multipath fading for realistic results. It should not be recommended to use an unqualified shielded environment (i.e. without specifying some level of lossy materials, etc. within that environment). Beyond that, this environment is redundant to the COTA environment.
Dr. Michael D. Foegelle, ETS-Lindgren

4. July 2006
Shielded Rooms
Shielded room (screen room) provides isolation but metal walls cause excessive multipath.
Far exceeds number of paths found in real world.
Dr. Michael D. Foegelle, ETS-Lindgren

5. July 2006
Shielded Rooms
Symmetry causes multiple identical paths for deeper fading than typically found in real world.
Signals reinforce each other in or out of phase.
Dr. Michael D. Foegelle, ETS-Lindgren

6. July 2006
Shielded Rooms
Energy bounces around until absorbed by other objects in the room or losses in walls.
Unpredictable from site to site.
Dr. Michael D. Foegelle, ETS-Lindgren

7. Example Comparison of Environments
July 2006
Example Comparison of Environments
Using a vector network analyzer, a NLOS arrangement was tested in several environments and the results compared.
Dr. Michael D. Foegelle, ETS-Lindgren

8. Example Comparison of Environments
July 2006
Example Comparison of Environments
The first environment was a conference room showing typical real world physical channel.
Dr. Michael D. Foegelle, ETS-Lindgren

9. Example Comparison of Environments
July 2006
Example Comparison of Environments
Frequency response shows typical multipath fading expected in physical channels.
Dr. Michael D. Foegelle, ETS-Lindgren

10. Example Comparison of Environments
July 2006
Example Comparison of Environments
The second environment was a small shielded control room with considerable loading.
Dr. Michael D. Foegelle, ETS-Lindgren

11. Example Comparison of Environments
July 2006
Example Comparison of Environments
Frequency response shows similar physical channel, but nulls are deeper and average signal level is higher.
Dr. Michael D. Foegelle, ETS-Lindgren

12. Example Comparison of Environments
July 2006
Example Comparison of Environments
The third environment was a large shielded room (reverb chamber) with little loading.
Dr. Michael D. Foegelle, ETS-Lindgren

13. Example Comparison of Environments
July 2006
Example Comparison of Environments
Physical channel is drastically different, with many more nulls and much higher signal levels.
Dr. Michael D. Foegelle, ETS-Lindgren

14. Example Comparison of Environments
July 2006
Example Comparison of Environments
Time Domain (from 5-6 GHz) shows expected exponential fall-off vs. path length for conference room environment.
Dr. Michael D. Foegelle, ETS-Lindgren

15. Example Comparison of Environments
July 2006
Example Comparison of Environments
Small shielded room with some loading shows higher initial pulse power levels and more linear fall-off.
Dr. Michael D. Foegelle, ETS-Lindgren

16. Example Comparison of Environments
July 2006
Example Comparison of Environments
Large shielded room with negligible loading (High Q) shows very little decay over long paths.
Dr. Michael D. Foegelle, ETS-Lindgren

17. Example Comparison of Environments
July 2006
Example Comparison of Environments
It’s evident that a shielded room doesn’t provide real-world physical channel, and therefore results won’t be reproducible without additional requirements.
Dr. Michael D. Foegelle, ETS-Lindgren

18. July 2006
Conclusion
COTA environment defines an OTA environment with a reproducible physical channel.
Section 5.7 should either be removed from the test plan and related topics harmonized with COTA environment.
Dr. Michael D. Foegelle, ETS-Lindgren

19. July 2006
References
1.       IEEE /0872r1, “Comments from TGT Internal Review ,” C. Wright.
Dr. Michael D. Foegelle, ETS-Lindgren