5 Jitter Separation in High Speed Digital Design FE · 2 2 2 exp σ x ... RPP DJ = J PP DJ The...

Jitter Separation in High Speed Digital Design

Gustaaf Sutorius

Jitter & Typical Digital Development Process

System

Design

Interconnect

Design

Active Signal

Analysis

Compliance

Test

• Accurate Design

Analysis

• Test & Analysis

CapabilityCapability

• Measurement

Automation

AGENDA 1. Jitter:

I. Definition and Description of Jitter

II. Understanding Jitter, its Components, and Separation

III. Jitter Measurement Methods and Tools

2. Actual jitter measurements

AGENDA 1. Jitter:






1. Definition and Description of Jitter

2. Understanding Jitter, its Components, and Separation

3. Jitter Measurement Methods and Tools

Jitter Primer: Topics to be Covered

• ‘Jitter ‘ is another word for shaky, quiver,

tremulous… speaks of degree of instability of

location.

• In the Digital Design world, jitter has been defined

as:

What is Jitter?

The short term phase variation of the significant instants of a digital signal from their ideal positions in time.

Ideal Location in Time (Reference)

ThresholdEarly

Transition

Instant

What is Jitter: Analyzing an Edge (Transition)

ThresholdLate

∆∆∆∆tEarly

JPP=∆∆∆∆tEarly Pk + ∆∆∆∆tlate Pk∆∆∆∆tLate

0 1

1) Seconds: if ∆∆∆∆tEarly =60 ps and ∆∆∆∆tLate=40ps

JPP= 100 pseconds

2) UI: Referenced to the Data Rate, called Unit Interval (UI):

Units for expressing Jitter

2) UI: Referenced to the Data Rate, called Unit Interval (UI):

For 2.5 Gb/s Data Rate, the UI (Period) = 400 pseconds

JPP= 100 pseconds/400 pseconds per UI = 0.25 UI

3) Radians: where there are 2ππππ radians per UI:

JPP= .25 UI x 2ππππ= ππππ/2 radians

Singletransition

x = 0

Eye CrossingPoints

x = Tx = 1/2 T

Left Edge Right EdgeNominal

Sampling Point

E1

E0

Jitter: Creating the Eye…

The EYE Diagram Unit Interval

Overlaidtransitions

Ideal Sampling Point

x = 0 x = Tx = 1/2 T

Oscilloscope Eye

Probability DensityFunction

Total Jitter, J PP

Why Care about Jitter?

• Bit Errors!

1

TransmittedWaveform 0 0 1 0 1 1 0

Received

1

ReceivedWaveform 0 0 1 0 1 1 0

1

InterprettedWaveform 0 1 0 1 1 01

Jitter as Horizontal “Timing Noise”

• A low “Signal to Noise Ratio”

causes errors

• Voltage Noise →→→→ vertical

fluctuations across the

sampling point

• Undesirable Amplitude

Modulation

• Undesirable Amplitude

Modulation

• Jitter describes the same

effect but horizontally –

timing noise

• Jitter →→→→ horizontal

fluctuations across the

sampling point

• Undesirable Phase

Modulation

Jitter – What Causes It?

• Oscillator Topology• PLL Design• Crystal Performance• Thermal Noise• Shot Noise• Dispersion • Reference Spurious•

Noise Mechanisms

System

• Radiated or Conducted Signals• Crosstalk• Duty Cycle Distortion mechanisms• Impedance mismatch• Inter Symbol Interference mechanisms• Receiver Detector characteristics• Clock/Data Recovery Design• PRBS Mechanisms

Data Dependent Mechanisms

System Mechanisms

Where ϕϕϕϕ(t) is overall system jitter function with many sources.

S(t): a general digital jitter signal and P(t): a pulse train

ϕϕϕϕ (t) is composed of functions ϕϕϕϕ (t) is composed of functions that

S(t)=P(Asin(2ππππfDt+ϕϕϕϕ(t)))

ϕϕϕϕ(t)= ϕ ϕ ϕ ϕ B(t) +ϕ ϕ ϕ ϕ UB(t)

Representing Jitter

ϕϕϕϕΒΒΒΒ(t) is composed of functions

that have Deterministic

(Bounded) phase deviations

because their max amplitudes

don’t change

ϕϕϕϕUΒΒΒΒ(t) is composed of functions that

have Random (UnBounded) phase

deviations because their max

amplitudes do change. The functions

are characterized by their statistics

Lets Look at the Jitter Sources Again…Oscillator TopologyPLL DesignCrystal PerformanceThermal NoiseShot Noise DispersionReference SpuriousRadiated or Conducted Signals

NoiseRANDOM / UNBOUNDED

Radiated or Conducted SignalsCrosstalkDuty Cycle Distortion mechanismsImpedance mismatchInter Symbol Interference mechanismsReceiver Detector characteristicsClock/Data Recovery DesignPRBS Mechanisms

Data

System

DETERMINISTIC

BOUNDED

Example Random and Deterministic Jitter

Deterministic Jitter (DJ): The spacing

between the mean values of the

“earliest” and “latest” traces, JPPDJ

Random Jitter (RJ):

Defined by RMS value, σ, of the Gaussian

distribution

JPPDJσ

Expressing Total Jitter• Usually represented as root-mean-square, Jrms, and peak-to-peak,

JPP

• Most useful to characterize jitter as a combination of JrmsRJ and JPP

DJ

at a given Bit Error Ratio (BER)

Random Jitter (RJ) – results from the accumulation of random processes.

• Assumed to Follow a Gaussian Distribution RJ contribution to Jrms is Jrms

RJ = σσσσ• Since a Gaussian function is unbounded ,

RJ contribution to JPP can be large JPPRJ →→→→ ∞∞∞∞

Deterministic Jitter (DJ) – results from systematic effects

• E.g., duty-cycle-distortion (DCD), intersymbol inte rference (ISI), periodic jitter (PJ), PRBS effects, and cros stalk

• DJ is bounded , JPPDJ is finite.

Sampling Point

Unit Interval

Gaussian

Jitter Only!

Random jitter: JPPRJ is related to Bit Error Ratio

x

Measure BER(x) = ββββ(x)

Overlap indicates BER

σL

Sampling Point

σR

µ µ

Jitter Only!

(No DJ)

JPPRJ = n××××σσσσ

Random Jitter JPPRJ : What factor to use ?

JPPRJ = n××××σσσσ

JPPRJ

Random jitter is UNBOUNDED, if we wait long enough we would have “hits” anywhere in the Eyediagram.

We could use any Berr but 10-12 is quite common to use and 10-12 equals to 14.1 sigma.

So if we measure sigma is 10 picoseconds, then we would say the random jitter is 141 Psec.

Expressing Total Jitter: RJ & DJ combined

• Since JPPRJ is unbounded, it can be defined by the BER that

would result if there were only RJ. This is where the tails of the right and left distributions overlap (at the Sampli ng point):

For a BER = 10-12 →→→→ JPPRJ = 14××××σσσσ

Then JPPRJ ≡≡≡≡ n××××σ σ σ σ so that JPP

RJ =nxJrmsRJ

• The Total Jitter (TJ), JTJ, for a given BER is then:

DJPP

DJPP

RJrms

TJ

J

JJnJ

+×=

+×=

σ14

This assumes that the Gaussian RJ PDF ‘appends’ to the DJ PDF

This is called the Dual Dirac Assumption

=∗

JPPDJ

The ‘DJ’ The ‘RJ’Total Jitter

7σ

The Dual Dirac Assumption

=∗ σ

µL

µR

µL

µR

)([ Lx µδ − ∗− )]( Rx µδ+

−

2

2

2exp

σx

−−+

−−=

2

2

2

2

2

)(exp

2

)(exp

σµ

σµ RL xx

No Jitter values

between deltas

Jitter Probability: BER

randomticdeterminispkpk nJJ σ×=−

=

Random and Deterministic Jitter

JPPDJ

σ = JrmsRJ

• Waveform Observation• Pattern• Note Characteristics

2 Distinct Falling Edges

2 Distinct Rising Edges

JPP Jrms

Falling Edges Rising Edges

Threshold

Lots of Zeros

Random and Deterministic Jitter• Lets Look at Deterministic Component…

JPPDJ

σ = JrmsRJ

JPPDJ

JPP Jrms

JLPPDJ JRPP

DJ

JLPPDJ + JRPP

DJ = JPPDJ

The Peak-to-Peak Deterministic value is the Delta b etween Worst case mean trajectories around a crossing poi nt .

Random and Deterministic Jitter• Now lets Look at the Random Component…

JPPDJ

σ = JrmsRJ

JPP Jrms

σσσσRJ σσσσRJ

σσσσRJ is a measure of the process that makes these traces wide

Random and Deterministic Jitter• Now lets Summarize Jitter for the Circuit Measured…

JPPDJ

σ = JrmsRJ

JPPDJ

σ σ σ σ =JrmsRJ

JPP Jrms

JPPT

JPPT = n x σσσσRJ + JPP

DJ

� Random Jitter (RJ) unbounded

• Due to thermal noise, shot noise, etc.

• Follows Gaussian distribution

• Requires statistical analysis to be quantified

Total Jitter is composed of random and determistic

components

Total jitter: Histogram View

• Requires statistical analysis to be quantified

• RJpp = 14.1 x Jrms for 10-12 BER

� Deterministic Jitter (DJ) bounded and composed of:

• Duty-Cycle-Distortion (DCD)

• Inter Symbol Interference (ISI)

• Periodic Jitter (PJ)

RJ

DJ

Deterministic Random

Signal jitter can be composed of several types from several mechanisms

Data-Correlated Data-Uncorrelated

Total

Jitter (TJ)ϕϕϕϕB(t)

Decomposing Jitter: The “jitter tree” DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Deterministic

Jitter (DJ)Random

Jitter (RJ)

Inter-symbol

Interference (ISI)

Duty Cycle

Distortion (DCD)

Periodic

Jitter PJ

Data Dependent Jitter

(DDJ)

Example: Duty Cycle Distortion (DCD)

Ideal Threshold

Actual Threshold

Transmitter Threshold Offset Problem

1 1

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

+ error

TIE Trend Waveform

- error + error - error

Clock

0 0

Note: One technique to test for DCD is to stimulate your system/components with a repeating 1-0-1-0… data pattern.

This technique will eliminat inter-symbol interference (ISI) jitter and make viewing the DCD within the spectrum display much easier.

Example: Duty Cycle Distortion (DCD)

Threshold

Transmitter Edge Transition Speed Asymmetry

1 1

0

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

- error + error - error + error

TIE Trend Waveform

Clock

0

Example: Inter-Symbol Interference (ISI)

Threshold

Transmission Line Bandwidth Limitation ProblemA

B

C

1

00

1 1 1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0 0

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

TIE Trend Waveform

““““A” = 0 preceded by string of 1’s = + error

““““B” = 1 preceded by 0 = - error

““““C” = 1 preceded by string of 0’s = + error

Example: Inter-Symbol Interference (ISI)Transmission Line Reflection / Improper Termination

Data Signal

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

TIE Trend Waveform

Each arrow shows which bit of data caused a reflection distortion

on a later data bit.

Example: Periodic Jitter (PJ)

Threshold

System Cross-talk Problem (capacitive coupling)

Corrupter

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Threshold

TIE Trend

Where Does Jitter Come From?

Transmitter Receiver

•Lossy interconnect (ISI)•Impedance mismatches (ISI)

Media

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

•Thermal Noise (RJ)•DutyCycle Distortion (DCD)•Power Supply Noise (RJ, PJ)•On chip coupling (PJ)

•Impedance mismatches (ISI)•Crosstalk (PJ)

•Termination Errors (ISI)•Thermal Noise (RJ)•DutyCycle Distortion (DCD)•Power Supply Noise (RJ, PJ)•On chip coupling (PJ)

.

ϕϕϕϕ(t ) = square wave

ϕϕϕϕ(t ) = mess

Different types of jitter ϕϕϕϕ(t) in S(t)=P(Asin(2ππππfDt+ϕϕϕϕ(t)))

Jitter examples for different Jitter Distributions

ϕϕϕϕ(t ) = AAppl sin (2 ππππ fJ t).

ϕϕϕϕ(t ) = pulse

ϕϕϕϕ(t ) = DDJ Only

A DCD B ISI

Jitter Examples Continued

C RJ (gaussian)l D Sinusoidal E ISI and DCD

Which Eye Has Worse Jitter?

You can’t know unless you measure the Total

Jitter or measure the jitter components!

A B

Jitter Measurement Solutions from Agilent

• Infiniium Scopes (up to 32 GHz):

• EZJit Software

• EZJit Plus Software

• DCA-J (86100 Series Infiniium 20-80 GHz Scopes)

• Jitter SW package

• Infiniimax Probes to 13 GHz

• N1930 Physical Layer Test System

• Vector Network Analyzer or Time Domain Reflectometer

• N4900 Series BERTs

• Bathtub curve Extrapolation and RJ/DJ Estimation

• E443x Signal Sources

• E4438C-SP1 Jitter Injection Software

Vector Network analyzer

Bit Error Ratio Tester

Pattern Generator

Transmitter Media Receiver

X

X

X

X

Time domain Reflectometer X

Tools to Measure/Analyze Jitter

X

X

Time Interval Analyzer

Equivalent time oscilloscope

Phase Noise Analyzer

Real time oscilloscope

Time domain Reflectometer X

X

X X

XX

X

X

Low Noise (RJ) available

Standard Patterns and User Definable Patterns

Flexible for wide variety of technologies.

RJ, PJ, and DCD can be created.

Pros

Cons

Jitter Tolerance Testing (w/Pattern Generators)

Cost Range: Modestly to Highly Expensive

Intersymbol Interference is not available.

Complex sequencing not available.

Cons

SinusoidalSquare

Tolerance Testing (using a Pattern Generator)

Sinusoidal, RJ and ISI*

* Created with cable length

Measures Total Jitter Directly

Can Provide good estimate of total Jitter quickly with BERTScan method

System Tool: Usable for Media analysis, receiver stress analysis

J-Bert N4903B available for jitter stress test

Pros

Jitter Analysis (BERTs)

Expensive

Time of Measurement of Total Jitter is Long

Need an external clock provided

Cons

Scan the sampling point, x, across the eye

Scan the sampling point across the eye

Measure BER(x) = ββββ(x)

Jitter Analysis: BERT BathTub Curve

TB0

0.5

10-3

10-6

10-9

10-12

BE

R

GaussianTails

0.5TB

Eye Opening atBER=10-12

β(x) ⇒ TJβ

x

Measure the Bit Error

ratio as a function of sampling point delay,

β(x)

Expensive

50 GHz BW available yields high

resolution

Highest Accuracy

VNAs TDRs

InExpensive

Limited by rise time of Pulse

source (35ps)

Accuracy may be sufficient in

Jitter Analysis: N1951A PLTS with Vector Network Analyzers

(VNAs) or Time Domain Reflectometers (TDRs)

Highest Accuracy

Full Differential Analysis

analysis to show EMI, mode

conversion locations

Software Modeling and Analysis

Available

S-Parameters for modeling or to

estimate ISI contribution of path

Accuracy may be sufficient in

many environments. Using

Normalization to increases

accuracy

Only magnitude TDT and TDR

Software Modeling and Analysis

Available

Differential Eye Diagram (from Agilent N1951A: VNA System)

Xaui Backplane differences because of transmission line length

30 inches15 inches

N1951A VNA Measurement of XAUI Backplane

Note increased striation because of BW limit of path

Note degree of eye closure

•Captures contiguous time record

•No external clock required

•Software clock recovery methods yield precise clock reconstruction

•System Tool: Usable for Debug

•Flexibility for many technologies and usually a growth path provided

•Many views provided for insight: histograms, eyes, fft, trend, data, etc

•Oscilloscope Bandwidths are going higher

Pros

Jitter Analysis (Real Time Oscilloscopes)

•Many views provided for insight: histograms, eyes, fft, trend, data, etc

•Oscilloscope Bandwidths are going higher

•Expensive

•Limited to current BW of scope

Cons

Agilent Infiniium Series Oscilloscopes

� High Bandwidth Models up to 32 GHz & 80 GSa/s per channel

� Deepest memory in the market up to 2 Gpoint per channel

� MegaZoom usable deep memory

� MegaZoom usable deep memory

� Mixed Signal Oscilloscope (MSO) models available

� Windows-Based Easy to Use GUI

� Drag-and-Drop easurements

� Zoom box

� Wide variety of analysis options

How Do Real Time Scopes Measure Jitter on Data: Ezjit Display

Jitter Trend

NRZ Serial Data

Recovered Clock

Trend

Jitter Spectrum

Units in Time

Units in Freq.

Jitter Histogram

Agilent E2681A EZJIT Jitter Measurement Application for Infiniium Oscilloscopes

Signal

Trend

Histogram

Trend

Spectrum

• Real Time (Single-Shot)

• Sequential Sampling (Repetitive)

Sampling Techniques

• Used with either Repetitive or Single-Shot Signals

• All Samples Are Taken From a Single Trigger

• Samples from Previous Triggers are Erased

• Sample Rate May Limit Scope’s Overall Bandwidth

• Best Resolution Depends Directly on Sample Rate

Real Time (Single Shot) TechniqueSampling

• Best Resolution Depends Directly on Sample Rate

EachTrigger

Identical

• Used ONLY with Repetitive Signals

• One Sample is taken for each Trigger

• Multiple Trigger Events Build Up Waveform

• Used in High Speed Applications with BW >10GHz

• No Pre-Trigger Information

Sequential Sampling TechniqueSampling

• No Pre-Trigger Information

1st Trigger2nd Trigger3rd Trigger

InExpensive

Bandwidth is Highest Available

Noise floor is good

Pros

Jitter Analysis (Equivalent Time Sampling Oscilloscopes)

Noise floor is good

TDR options for media analysis

Flexibility for increasing rates

Industry leading jitter separation algorithm (DCA-J)

External Clock or Clock related trigger is required or

Hardware Clock Recovery Module

Cons

Jitter Analysis (Equivalent Time Oscilloscopes)

A

B

Which Eye Has Worse Jitter? DJPP

DJPP

RJrms

TJ

J

JJnJ

+×=

+×=

σ14

A B

Jitter Measurements on an equivalent Time

Sampling Oscilloscope, 86100C DCA-J

Completely new technique for jitter analysis

Pattern Lock + Eyeline

internally generated pattern trigger + individual trajectories /

averaged eyes

�� Jitter Mode – jitter analysis at any data rate!

�� Jitter Mode – jitter analysis at any data rate!

“Swiss army knife”

• Wide bandwidth scope

• eye-diagram analysis

• Time Domain Reflectometer

• Jitter analyzer

DCA-J Measurement Architecture• Eliminate historical weaknesses

• New triggering hardware enables efficient sampling

• Built in pattern trigger – Pattern Lock

• Determines pattern length and counts clock pulses

• Enables precise sampling position within the eye so every

sample is used for jitter analysis

• Minimizes errors from timebase delay

Separate Correlated and Uncorrelated Jitter

Uncorrelated:

• Counter hardware focuses samples on edges

• Pattern lock – focus on specific edges

• Analyze jitter uncorrelated to the pattern:

random jitter and periodic jitter (RJ ∗∗∗∗ PJ)

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Correlated:

• Pattern lock – average every

edge

• Analyze jitter correlated to the

pattern:

data dependent jitter (DDJ)

Obtain DDJ vs. Bit record of edge positions• DDJ for a given edge is the difference

Data Dependent Jitter (DDJ)Average out the uncorrelated jitter using Pattern

Lock• Isolates data-correlated contributions only

Measure mean position of every edge in pattern• Ideal edge position defined mean of means

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

• DDJ for a given edge is the difference between its average position and the ideal

• Peak-to-peak DDJ is difference between earliest edge and latest edge

Build histograms for• All edges• Rising edges• Falling edges

Duty Cycle Distortion (DCD) &

Inter-Symbol Interference (ISI)

• Isolate rising edge data from falling edge data

• Difference of average locations is JDCD

• |µµµµFalling - µµµµRising|

• Maximum of the peak-to-peak values is JISI

• Max (P-to-PFalling , P-to-PRising)

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

µF µRDCD

DDJ

P-PF

P-PR

Data-Uncorrelated JitterFocus on only one edge at a time• Isolates uncorrelated contributions

Build a time sampled record• Periodic samples of uncorrelated jitter

Late

Early

Time

Jitte

r

Counter hardware provides

precise periodic sampling

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Early

Build a histogram of uncorrelated jitter• RJ, PJ Histogram

Late

Early

Time

Jitte

r

FFT time sampled record• Aliased jitter frequency spectrum• Shows RJ & PJ – PJ appears as spikes

Random Jitter (RJ) DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Integrate ‘noise’ power in resultant spectrum…• This is the random jitter (RJ)

Remove PJ spikes from spectrum• Interpolate across gaps left behind• Resultant spectrum is made up of RJ

PJ spikes NOT

used to derive

PJ value

Periodic Jitter (PJ)

Take RJ info from FFT and construct a Dual Dirac-delta model with appropriate slopes

Match Dual Dirac-delta model to RJ, PJ

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Match Dual Dirac-delta model to RJ, PJ histogram so that peak-peak widths match for

99.8% of volume

Separation (offset) of two Gaussians corresponding to the match is the

periodic jitter (PJ).

Deterministic Jitter (DJ) and

Total Jitter (TJ)

• DDJ histogram (Data-Correlated)

and RJ, PJ histogram (Data-

Uncorrelated) are measured

directly

• Convolution of these histograms *

DDJRJ, PJ

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

• Convolution of these histograms

produces a histogram

representing the PDF of all of the

jitter present – Total Jitter

histogram

*Aggregate

Jitter

Deterministic Jitter (DJ) and

Total Jitter (TJ)

Match Dual Dirac-delta model to TJ histogram so that peak-peak widths match for 99.8% of volume

• Same technique as used to get PJ from RJ, PJ PDF

Take RJ info from FFT and construct a Dual Dirac-delta model with appropriate slopes

DJ

DJ RJ

DDJ

ISI DCD

PJ

Correlated UncorrTJ

Extrapolate down the resultant Dual Dirac-delta model to the effective BER of interest

(typically 10-12) peak-to-peak deviation is TJ

DJ Separation (offset) of two Gaussians corresponding to the match is the

deterministic jitter (DJ)

Seeing the Complete Jitter Picture

New: N5400A EZJIT Plus Jitter Separation

= DCA-J algorithm on a real-time oscilloscope

N5400A EZJIT+ simplifies jitter compliance

EZJIT and EZJIT Plus Measurements• E2681A EZJIT Jitter Analysis

• Single-Source

• Period

• Frequency

• Positive/Negative pulse width

• Duty cycle

• Rise/Fall time

• Dual-source

• Setup/Hold time

• Phase

• Clock

• N5400A EZJIT Plus Additions*

• RJ/DJ Separation Components

• Random jitter (RJ)

• Deterministic jitter (DJ)

• Data-dependent jitter

• Inter-symbol interference (ISI)

• Duty cycle distortion (DCD)

• Periodic jitter

• Total jitter at user-selectable bit error rate

• Display Views

• RJ/PJ histogram

• Clock

• Time-interval error (TIE)

• Cycle-to-cycle jitter

• N-cycle jitter

• Cycle-cycle positive/negative pulse width

• Cycle-cycle duty cycle

• Data

• Time-interval error (TIE)

• Data rate

• Unit Interval

• RJ/PJ histogram

• TJ histogram

• DDJ histogram

• Composite histogram (TJ, DDJ, RJ/PJ)

• Jitter spectrum (zoomable)

• DDJ vs. bit (for repeating patterns)

• Bathtub curve (eye-opening vs. BER)

• N5400A and E2681A common display views

• Measurement trend

• Histogram

• Jitter spectrum *N5400A includes all features of E2681A

as well as the following

• Jitter is a complex phenomena and understanding and measuring it can be as

well.

• Having a Total Jitter to achieve a desired Bit Error Ratio is the main goal for any

digital interface.

• Jitter Separation is an Enterprise Jitter methodology to deliver an estimate of

Total Jitter quickly.

• There are many methods to separate jitter in our next paper we will see they can

give different results. The results for TJ are often 15-25% in error—almost

Summary

give different results. The results for TJ are often 15-25% in error—almost

always an overestimate of TJ.

• There are many tools that can be used in the testing for jitter. Which ones you

select are dependent on your tasks, future projects, size, and your comfort level.

www.agilent.com/find/jitter Jitter meas. solutions

www.agilent.com/find/jitter_info Jitter app. info.

www.agilent.com/find/si Signal Integrity Solutions

Results Agilent Jitter Accuracy Study (Jitterfest 3)

TJ Estimate vs Actual TJ

225

300

Fas

t TJ

Est

imat

e (p

s)

BERT

TRUE

DCA-J

DSO81304A/N5400A EZJIT Plus

0

75

150

0 50 100 150 200 250Actual TJ (ps)

Fas

t TJ

Est

imat

e (p

s)

DSO81304A/N5400A EZJIT Plus

AGENDA 1. Jitter:





Actual Jitter Measurements• 86100D as jitter analyzer

• 81134A as pattern generaror

• Demo 1: measure ISI jitter with bnc cable as “ISI injector”

• Demo 2 : measure uncorrelated Pj and Resolve Pj frequencies

with MXG as uncorrelated Pj source

with MXG as uncorrelated Pj source

•Questions?

5 Jitter Separation in High Speed Digital Design FE · 2 2 2 exp σ x ... RPP DJ = J PP DJ The...

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Transcript of 5 Jitter Separation in High Speed Digital Design FE · 2 2 2 exp σ x ... RPP DJ = J PP DJ The...