LeCroy Advanced Analysis for High Speed Data Stream
Transcript of LeCroy Advanced Analysis for High Speed Data Stream
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Advanced Analysis
for High Speed Serial Data Stream
Advanced Measurements not only Signal Integrity - Ju ly2009
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Agenda
BER Contours mapping ( Iso-BER)
Concepts
Benefits
Advanced Signal Integrity Measurements Methods:
High Speed Serial Data Challenge
What Bandwidth for Serial Data Signal ? Improve accuracy and add precision to measurements :
De-embedding methods
Emulating methods
Equalization :
Equalized System and Measurement Challenges
Transmitter emphasis
Receiver equalization
Equalization methods combined with jitter measurements
Advanced Analysis for High Speed Data Stream
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Agenda
BER Contours mapping ( Iso-BER)
Concepts
Benefits
Advanced Signal Integrity Measurements Methods:
High Speed Serial Data Challenge
What Bandwidth for Serial Data Signal ? Improve accuracy and add precision to measurements :
De-embedding methods
Emulating methods
Equalization :
Equalized System and Measurement Challenges
Transmitter emphasis
Receiver equalization
Equalization methods combined with jitter measurements
Advanced Analysis for High Speed Data Stream
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BER Contours mapping Iso-BER)
Show the est imated eye closure o f the eye pattern after col lect ing a certain
number of UI in th e eye pattern ( UI=BER
-1
) Al low s the abi l i ty to measure noise impact on ampl i tude as wel l as on j i t ter
Ident i fy always crosstalk design issu es:
Also in case aggressor transitions are not incident with signal victim transitions and
therefore jitter data are not impacted.
BER Contours displayed
from 10-6
to 10-12
Advanced Analysis for High Speed Data Stream
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Advanced Analysis for High Speed Data Stream
BER Contours No Crosstalk
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Advanced Analysis for High Speed Data Stream
BER Contour With Crosstalk
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Agenda
BER Contours mapping ( Iso-BER)
Concepts
Benefits
Advanced Signal Integrity Measurements Methods:
High Speed Serial Data Challenge
What Bandwidth for Serial Data Signal ? Improve accuracy and add precision to measurements :
De-embedding methods
Emulating methods
Equalization :
Equalized System and Measurement Challenges
Transmitter emphasis
Receiver equalization
Equalization methods combined with jitter measurements
Advanced Analysis for High Speed Data Stream
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High Speed Serial Data Stream
Advanced Analysis for High Speed Data Stream
Signal speeds and data rates have increased into the frequency range
while propagation mediums remained unchanged !
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Agenda
BER Contours mapping ( Iso-BER)
Concepts
Benefits
Advanced Signal Integrity Measurements Methods:
High Speed Serial Data Challenge
What Bandwidth for Serial Data Signal ? Improve accuracy and add precision to measurements :
De-embedding methods
Emulating methods
Equalization :
Equalized System and Measurement Challenges
Transmitter emphasis
Receiver equalization
Equalization methods combined with jitter measurements
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Cable/Fixture/Serial Data Channel
De-embedding
De-embedd ing g ives the user
the abi l i ty to view their
waveform s as if the
cable/f ixtur e/serial data channel
was no t present .
Cable/f ixtu re/serial data chann elef fect is def ined by user-
sup pl ied S-parameter f i le.
Should be always don e when
frequency content is increas ing
into the m icrowave range
Advanced Analysis for High Speed Data Stream
Cables and fixtu re de-embedd ing
effects on a PCIs Gen 2 signal
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Serial Data Channel Response
Emulation
Channel emu lat ion gives the
user the abi l i ty to view theirwaveform as if i t were passing
throu gh a ser ial data channel
that isnt present.
The channel effect is def ined by
a us er-sup pl ied s-parameter
f i le.
Useful to model wors t-case
scenar ios and unders tand how
design margins are maintainedin thos e s i tuat ions
(Input)
(Output)
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Agenda
BER Contours mapping ( Iso-BER)
Concepts
Benefits
Advanced Signal Integrity Measurements Methods:
High Speed Serial Data Challenge
What Bandwidth for Serial Data Signal ? Improve accuracy and add precision to measurements :
De-embedding methods
Emulating methods
Equalization :
Equalized System and Measurement Challenges
Transmitter emphasis
Receiver equalization
Equalization methods combined with jitter measurements
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Equalization (simplistic view)
For a given frequency, loss is
propo r t ional to length For a given leng th, loss is
propo r t ional to frequency.
Channel qual i ty depends on lo ss
character is t ics v s. frequency and
length
Serial Data Equal izat ion is usin g
same methods used prev ious ly in
the telecommunicat ion at longer
distance : 2.5 GHz over 30 in. is equivalent as 1
MHz over 1 mi. ( 1.6 Km)
1
frequencylength
lossQ
Qlosslengthspeed acceptable
miMHzinGHz 11305.2
Equal izat ion inc reases the acceptable loss n umber, thereby inc reasing
either speed or length o r both ,
0 110
0
frequenc y (MHz)
m
agnitude(dB)
0 210
0
frequency (GH z)
m
agnitude(dB)
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Equalized System Measurements Challenge
Backplane
TransmitterReceiver
Eq
Differential
Probe
For very fast data rates (>5 Gb/s), the
transmitter signal typically has very
good signal integrity. However, after
propagating through the backplane,
this signal will become severely
degraded.
At the far end of the channel, the eye is
closed. The signal at the receiver pins
(which can be probed) is not the signal of
interest. The equalized signal inside of
the receiver chip (which cannot be
probed) is the signal of interest.
The equalized signal within the
receiver chip cannot be probed.
How can this signal be validated to
ensure low jitter, a clean eye
pattern, and good signal integrity?
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Transmitter Emphasis
Pre-Emphasisboosts the high frequency
compo nents whi le leaving the low
frequency com ponents unchanged
Advanced Analysis for High Speed Data Stream
De-Emphasis attenuates the lowfrequency com ponents whi le
leaving the h igh frequency
compo nents unchanged
Transmitter designers employ the use of emphasis to
pre-compensate the disproportionate impact on the high
frequency content of the serial data channel0 5 106050
40
30
20
10
0
frequency (GHz)
magnitude(dB)
.
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Feed Forward Equalization (FFE)Receiver Equalization
Hinted at , from the frequ ency
respon se , com pensate frequencyloss of the ser ial data channel
Corrects the received waveform
vol tage value us ing prev ious
values and no t decoded data (
DFE).
Delay is u sual ly 1 UI
Tap value is th e gain of th e
amp li f ier in that stage
Each s tage is then added tog ether
to create the outp ut waveform
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Continuous Time Linear Equalization (CTLE)
*Image sourc e USB-IF
Advanced Analysis for High Speed Data Stream
Emphasize the high frequenc y con tent on the receiver side
CTLE Auto Mode allows the user to sp ec i fy the amoun t of boo st in dB
CTLE Custom mode al low s the user to def ine DC Gain, Zero, Pole 1 and
Pole 2 Frequencies
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Agenda
BER Contours mapping ( Iso-BER)
Concepts
Benefits
Advanced Signal Integrity Measurements Methods:
High Speed Serial Data Challenge
What Bandwidth for Serial Data Signal ? Improve accuracy and add precision to measurements :
De-embedding methods
Emulating methods
Equalization :
Equalized System and Measurement Challenges
Transmitter emphasis
Receiver equalization
Equalization methods combined with jitter measurements
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Equalizationand Jitter Measurements
Extend Jitter and Eye pattern analysis to equalized systems
Allows full signal integrity measurements made from a receivereye view :
Jitter and Eye measurements representative of actual system performance
Accurate Performance Margin measurements on the receiver signal
Tell you what the jitter looks like under various equalized
situations
How much equalization is required for how much ISI reduction ?
How much equalization is increasing Rj ( Noise ) ?
What the transmitter jitter looks like without pre or de-emphasis ?
Advanced Analysis for High Speed Data Stream