Characterizing 11G Long Reach CEI Channels

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Characterizing 11G Long Reach CEI Channels

• John Mitchell
• Winchester Electronics

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Agenda
Characterizing 11G Long Reach CEI Channels

• Introduction to CEI
• Definition of a channel
• How to characterize channel performance
• Accounting for the driver, receiver and data
• An eye pattern based on statistics
• Conclusions

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What is CEI?

• Next Generation Common Electrical I/O Project
• Will support various higher level interfaces
  including
• SFI (SERDES to Framer Interface)
• SPI (System Packet Interface)
• TFI (TDM-Fabric to Framer Interface)
• Higher Density and/or lower cost interfaces for
  data rates up to 10Gbps.

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What is CEI?

• Four versions are defined
• A 6G short reach link
• 0 to 200mm link with up to one connector
• Data lane(s) that support bit rates from 4.976 to
  6Gbps over Printed Circuit Boards.
• A 6G long reach link
• 0 to 1m link with up to two connectors
• Data lane(s) that support bit rates from 4.976 to
  6Gbps over Printed Circuit Boards.
• An 11G short reach link
• 0 to 200mm link with up to one connector
• Data lane(s) that support bit rates from 9.95 to
  11Gbps over Printed Circuit Boards.
• An 11G long reach link
• 0 to 1m link with up to two connectors
• Data lane(s) that support bit rates from 9.95 to
  11Gbps over Printed Circuit Boards.

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Typical Long Reach Application
Backplane
Total Transmission Line Length up to 1 meter.
Transceiver
Transceiver
Plug-in Card A
Plug-in Card B
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Reference Model
Driver Characteristics
Channel Characteristics
Receiver Characteristics
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Long Reach Issues

• Significant loss at high frequency
• Significant loss dispersion over required
  bandwidth
• Numerous transmission line transition points may
  cause reflections
• Potential Skew Issues
• Potential Crosstalk Issues
• Various signal conditioning options

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How to characterize the channel?
Time Domain
Frequency Domain

• Pattern dependent
• Eye may be closed
• Can signal conditioning help?

• How much loss is too much?
• How does this relate to the time domain?
• Can signal conditioning help?

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Pulse Response Method
H(?)
H(?)
Frequency Domain
Interpolate Extrapolate
DUT
Channel Measurement
Channel Response
S-Parameters
iFFT
Characterize Total Channel Distortion
Tx(t)
H(t)
Rx(t)
Amplitude


Time Domain
Jitter
Transmit Pulse
Channel Response
Pulse Response
Thru Channel and Crosstalk Channels
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Input Pulse
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Input Pulse and Channel Response
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Pulse Response Analysis

• C0 cursor is placed at peak
• Pre and Post cursors are placed at baud spaced
  intervals
• Pre and Post cursors represent distortion
• Relationship between C0 and the sum of all other
  cursors can be used to characterize the channel
• The probability of cursors causing distortion can
  be determined based on the data pattern being
  transmitted on the channel

C0
C1
C2
C3
C4
C-1
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Drivers and Receivers are not Perfect
Driver will jitter pulse in time
Receiver may not sample at peak
C0
C1
C2
C3
C4
C-1
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Each Cursor has a Range of Values

• Probability of driver and receiver behavior can
  be determined
• This will set bounds on possible cursor positions
  for a given number of bits

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Crosstalk must be Added
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Thru and Crosstalk Channel Pulse Response
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Statistical Calculations on Measured Data
Pulse Response
These calculations can be automated and
incorporated into test equipment or Matlab program
Data Pattern Statistics

Driver Jitter Statistics

Receiver Sampling Statistics
Statistical Data Eye


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Statistical Data Eye

• Each contour line represents the statistical eye
  opening for a given number of bits
• The most red eye in this case represents BER of
  1e-15

Courtesy of Anthony Sanders (Infineon
Technologies)
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Conclusion

• OIF is developing a new method to characterize
  interconnect channels
• Basis for characterization is measurement with
  VNA (complete and accurate)
• The new method accounts for statistical variation
  in the data pattern and performance of driver and
  receiver
• Results are in familiar Time Domain format and
  easy to interpret

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Technology Demonstrations at Supercomm

• Active test set-up in OIF Booth
• Passive test set-up on Winchester Booth
• Hall C3 - Booth 11831