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Presenter: Allen Duncan April 10, 2003

Presenter: Allen Duncan April 10, 2003. Highlights of the Last Week. Tested Receiver without optical link Used Al shield to determine EMI presence Conducted FFT analysis on Power Supply. Review of Last Presentation. Better Results at 5 dB atten. when transmitter on.

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Presenter: Allen Duncan April 10, 2003

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  1. Presenter: Allen DuncanApril 10, 2003

  2. Highlights of the Last Week • Tested Receiver without optical link • Used Al shield to determine EMI presence • Conducted FFT analysis on Power Supply

  3. Review of Last Presentation • Better Results at 5 dB atten. when transmitter on. • Is the signal we see crosstalk? 5 dB attenuation with TX OFF 5 dB attenuation with TX ON

  4. Remove Optical Link • Q: Will Eye diagram remain w/out optical link? • A: YES No Optical Link PRBS7 No Optical Link D21.5

  5. Removing Optical Link • Q: Eye diagram remains, What does this mean? • A: Cross-talk between Transmitter and Receiver is sufficient enough to create its own Eye • Q: Does this cross-talk cause a problem in the functionality of the tranceiver? • This is yet inconclusive. A more sensitive PD, or stronger signal may overcome such X-Talk.

  6. X-Talk experiments: Shielding • Shielding between entire TX and RX Eye Diagram with RX/TX shield Aluminum Shield Setup between TX and RX

  7. X-Talk experiments: Shielding • Shielding specific components No Shielding VCSEL shielding SMA shielding PD shielding

  8. X-Talk experiments: Shielding • Shielding Conclusions • More evidence there is EMI between RX and TX • X-Talk Eye disappears only when RX and TX modules are completely shielded • When PD is shielded some degradation of signal is obtained but Eye is still visable

  9. Power Supply Noise • At least 2 frequencies present Zoom of high frequency part of noise Noise on PS – at least 2 freq present

  10. More about noise and crosstalk • Significant noise similar to that on the Power Supply was measured in the air as well • Moving Foil Shield around produced weird results Eye diagram with Foil shield in random position

  11. FFT Analysis • Spikes at several Frequencies • ~3 MHz • ~330 MHz • ~660 MHz • ~1.25 GHz

  12. Plans for the Coming Week • Unconnectorized PD – Alignment tolerance • Find and purchase more sensitive PD • Determine solutions to no signal at 5 dB • Determine ultimate role of X-Talk in disturbance of signal

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