LeCroy Advanced Analysis for High Speed Data Stream

8/10/2019 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


Concepts

Benefits





Emulating methods

Equalization :







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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

http://localhost/var/www/apps/conversion/tmp/scratch_5/IsoBER3.exe


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BER Contours No Crosstalk


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BER Contour With Crosstalk


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Agenda


Concepts

Benefits





Emulating methods

Equalization :







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High Speed Serial Data Stream


Signal speeds and data rates have increased into the frequency range

while propagation mediums remained unchanged !


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Agenda


Concepts

Benefits





Emulating methods

Equalization :







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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


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


Concepts

Benefits





Emulating methods

Equalization :







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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


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


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


Concepts

Benefits





Emulating methods

Equalization :







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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 ?


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LeCroy Advanced Analysis for High Speed Data Stream