presenter: allen duncan april 10, 2003
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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
Aluminum Shield Setup between TX and RX
Eye Diagram with RX/TX shield
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
Noise on PS – at least 2 freq present Zoom of high frequency part of noise
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
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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