Dijagram Oka

This document is owned by Agilent Technologies, but is no longer kept current and may contain obsolete or

inaccurate references. We regret any inconvenience this may cause. For the latest information on Agilent’s

line of EEsof electronic design automation (EDA) products and services, please go to:

www.agilent.com/fi nd/eesof

Agilent EEsof EDA

nstewart

Text Box

Eye Diagram Measurements in Advanced Design System

Group/Presentation TitleAgilent Restricted

Month ##, 200XPage 1

Eye Diagram Measurements in

Advanced Design System

Page 2

Eye Diagram Measurements in ADS

Page 2

Agenda

• Why an Eye Diagram ?

• Eye Diagram Measurements in ADS.

• Frequency Domain Analysis of an Interconnect.

• Optimization of an Equalizer Performance.

Page 3


Page 3

Why create an Eye Diagram?

Difficult to Characterize a Waveform

Page 4


Page 4

Interconnect/Transmitter- Good or Bad?

Page 5


Page 5

Eye Diagram Functions In ADSTwo eye diagram functions in ADS• eye(node_name, data_rate, number_of_cycles, delay)• FrontPanel_eye( node_name, data_rate, number_of_cycles, delay)

Difference between two eye functions

Unit Interval

…

Page 6


Page 6

Characterizing an Eye DiagramEye diagram parameters• Eye level 1 & level 0

• Eye rise/ fall time

• Eye opening

• Eye width

• Eye height

• Eye amplitude

• Eye signal to noise ratio

• Peak to peak & RMS jitter

• …

50 psec delay

FrontPanel_eye( node_name, data_rate, number_of_cycles, delay)

Page 7


Page 7

Eye Binning Function

451 Columns32

1 R

ows

Eqn = eye_binning( eye_plot,num_x_bins,num_y_bins)

Outer IndependentInner Independent

Number of Traces

Page 8


Page 8

Histogram PlotsMajority of Eye calculations are based on histogram plotsTwo types of histograms

• Horizontal histogram - For every time point, sum up the number of traces across vertical binsFrontPanel_eye_horizontal_histogram()

• Vertical histogram – For every amplitude point, sum up the number of points across time axisFrontPanel_eye_vertical_histogram_index()

Statistical calculation• Mean value, Standard Deviation ( 1 σ ), and

Three Standard Deviation ( 3 σ )Frontpanel_get_histogram_mean_stddev ()

Page 9


Page 9

Calculate Eye DelayEqn=FrontPanel_eye_delay(Waveform_Data,Default_DataRate,Data_Type)Function calculates the time delay required to position eye crossing at the center of the UI (Only applicable to NRZ type data)

Creates Eye DiagramConvert Eye data to bin dataDetermine Max and Min amplitudeCreate horizontal histogram in a narrow stripFind Mean value of horizontal histogramCompare Mean position as compared with UI/2

Calculated Delay

Delay calculation is required for automated eye parameter measurements.Binning the eye diagram makes this calculation easy.

Page 10


Page 10

Eye Crossing Measurements

Create horizontal histogram across a narrow central strip

The mean value provides eye crossing

time

Create vertical histogram @ mean crossing time points

The mean value will provide eye crossing

amplitude Mean Value of Horizontal Histogram Give Eye Crossing Time Value

Mean Value (Eye Crossing Amplitude Point)

Page 11


Page 11

Measurements of Eye Level One/Zero

Level zero

Upper half

Lower half

0% 40% 60%Measurement boundaries

Level one

100%

Determine Eye Crossing points ( t1, t2)

Determine (40-60% ) Eye

Boundaries

Calculate vertical histograms in upper half

region

Calculate Level One Mean & Standard

Deviation

Calculate vertical histograms in lower half

region

Calculate Level Zero Mean & Standard

Deviation

Page 12


Page 12

40-60% Region

Zero level histogram mean

Upper half

Lower half

One level histogram mean

Eye Amplitude = Level One – Level Zero

Measurements of Eye Amplitude, Height, and S/NEy

e Am

plitu

de

3 σ

3 σ

Eye Height = (Eye level one- 3σ)- (Eye level zero+3σ)

Eye

Heigh

t

1 σ

1 σ

Eye S/N= (Eye level one-Eye level zero)1σ level one+1σ level zero

Page 13


Page 13

Measurement of Eye Width

Eye width = (Eye crossing@t2- 3σ)- (Eye crossing@t1+3σ)

Eye Width3 σ

t1 t2

3 σ

Calculate Eye Crossing points

Calculate Horizontal Histograms around Eye

Crossing Amplitude

Calculate Mean value and Standard Deviation

Calculate Eye Width

Page 14


Page 14

Calculating Rise Time

Horizontal histogram plot for 20% threshold



Plot single Eye Diagram with delay

Determine Level One and Level Zero

Get the Rising Edgeswhich qualifies forall three thresholds

Calculate Horizontal Histogram for Qualified

Edge @ all three threshold values

Calculate Mean value for all three histograms

Rise time is the difference between the

Mean value of Histograms @ low and

high threshold

Page 15


Page 15

Jitter Histogram

Jitter Histogram - Horizontal histogram across Eye Crossing point.Standard Deviations - Represents RMS Jitter ( If only Random Jitter is present)Peak to Peak Jitter is the histogram width

Jitter (p-p)

Page 16


Page 16

Eye Diagram FrontPanel • Automated measurements using Eye Diagram FrontPanel

In addition to eye diagram measurements, it performs many waveform parameter measurements

Page 17


Page 17

Compare Eye FP to DCA on same waveform

DCA Measurement

1G Data Rate through 20” trace

Eye Diagram FrontPanel on the DCA output file.

[NOTE: FrontPanel data is from a single trace. DCA measurements are averaged with 16 measurements.]

FrontPanel DCA typ DCA min/max

Level 1 212mV 211.3mV 211.3/213.5

Level 0 -177.4mV -177.5mV -177.5/-178.5

Rise Time 219pS 222pS 219/226

Fall Time 212pS 215pS 211/219

Eye Amp 389.4mV 389mV 386.3/389.4

Eye Height 274.7mV 274.7mV 273.9/274.9

Eye S/N 10.18 10.07 10.01/10.23

Jitter p-p 22.2pS 22.2pS 22.2/22.2

Jitter rms 5.8pS 5.7pS 5.7/5.8

ADS Eye Diagram FrontPanel

Page 18


Page 18

Case Study

Design an equalizer to improve eye diagram performance

– Frequency domain simulator to predict channel performance– Simulation of a channel with equalizer– Optimization of an equalizer for eye performance

Page 19


Page 19

Channel Simulation

Various interconnect models

Page 20


Page 20

Time Domain Simulation (Convolution)S-Parameter representationof the channel

For this example, channel is just a passive interconnect.

Can one use frequency domain simulators?

Page 21


Page 21

Why use Frequency Domain Simulators?• No exclusive time domain components (IBIS model)

• Fast simulation

• Accurately accounts for all the frequency domain effects

• Availability of frequency domain bit sequence source

• No convergence issue

• Voltage at any node can be converted to time domain

• Eye diagram measurements can be accomplished

• Extremely fast and accurate simulation

Requirement: S-parameter/models should have sufficient bandwidth to satisfy the time sampling requirement

Limitation: Cannot be used with IBIS models (Rise and fall tables are defined as the timing waveforms )

Page 22


Page 22

AC Simulation of Channel Model

AC simulation setup

Frequency domain simulation Time domain characterizationWhat we are trying to accomplish?

Page 23


Page 23

Comparison shows good correlation.

Comparing Time and Frequency Domain Simulation Results

Time Domain SimulationFrequency Domain Simulation

Calculate eye parameters?

Page 24


Page 24

Characterizing Eye Diagram using ADS FrontPanel

Eye diagram measurements

Can one measure eye parameters during simulation?What are the advantages?

Page 25


Page 25

Eye Diagram Measurements during Simulation

Eye diagram measurement equations defined on the schematic page.

Page 26


Page 26

What we are achieving?

• Running AC simulation

• Plotting time domain waveform

• Plotting eye diagram measurements

Advantage• Fast and accurate channel simulation

• No convergence issues

• Measure eye diagram performance

Download example project from ADS knowledge website.

Provides simulation setup and measurement equations.

Frequency domain simulation Time Domain Characterization

Page 27


Page 27

Eye Diagram Measurements

Is Eye Performance Acceptable?How to improve eye diagram performance?

Page 28


Page 28

Why Equalization?As data rate increases, the frequency response and attenuation

characteristics of PCB traces degrade signalsEnables channel to operate at higher data rates

faster, better, cheaper

How to negate channel effects?

Page 29


Page 29

Consider Passive Equalizer Design A high pass filter

How to determine equalizer parameters?

Page 30


Page 30

Comparing Simulation Results

Without Equalizer With Equalizer

Eye height and Jitterp-p is improved.Can equalizer design be further improved?

Page 31


Page 31

Optimize Equalizer Design for Eye Opening

The goal is to optimize equalizer design to maximize Eye Opening

Goal: Improve Eye Opening Factor from 0.59 to 0.9

Parameter to be optimized

Page 32


Page 32

Eye Parameter Measurements and Optimization

Optimizing Eye Opening Factor

Eye Measurements

Frequency Domain Simulation

Change in the reactive element value will change the flight time. Will the optimization goals works with varying flight time?

Page 33


Page 33

Advantages

• Works well even if the flight time delay is changed due to changein the reactive element value.

• Automatically calculates delay required for eye positioning

• Automatically detects eye crossing point and 40-60% region

• Optimize eye diagram performance

Any eye diagram parameter such as eye opening factor, eye height, peak to peak jitter, rise time … can be used as an optimization goal.

• Unique and extremely powerful• Essential for state of the art serial link design

Frequency domain simulation Time domain characterizationTime domain optimization

Page 34


Page 34

Optimizing Eye Diagram ParametersLimitation: One cannot send Eye Diagram Measurements to data display during optimization

Deactivate output Node Voltage and Measurement Equations while performing optimization ( Defined in Simulator Controller)

Page 35


Page 35

Optimized Value of Equalizer Components

Page 36


Page 36

Comparing Simulation Result

Eye Diagram without equalizer Eye Diagram with optimized equalizer

Improvement in Jitter

ADS Eye Diagram plots

Page 37


Page 37

ADS Waveform in DCA – without Equalization

ADS simulated waveform was sent to DCA for post processing

DCA Eye Diagram display showing ADS simulated waveform

ADS Eye Diagram

Page 38


Page 38

Eye Jitterp-p 15.7 psEye Signal to Noise 4.75

Eye Rise Time 33 psec

ADS Waveform in DCA with EqualizationDCA Eye Diagram display showing ADS simulated waveform

ADS Eye Diagram

Page 39


Page 39

Comparing Simulation Results

Channel+ Equalizer before Optimization Channel+ Equalizer after Optimization

Optimizer type – Random optimizerNumber of iterations – 40Optimization time – 15 Minutes

Page 40


Page 40

Conclusion• ADS has been used for SI design for over 20 years

• ADS has a multitude of accurate built in models

• ADS allows you to build accurate physical models

• ADS brings IP, simulation and measurement together

• Reviewed Eye Diagram measurement algorithms in ADS• ADS allows you to predict time domain performance using frequency domain simulators

• Allows you to characterize and optimize Eye Diagram Performance

You can optimize eye diagram performance not only using the AC simulator, but ADS also allows you to optimize interconnects for eye diagram performance using numeric, time and other frequency domain simulators.

www.agilent.com/fi nd/emailupdatesGet the latest information on the products and applications you select.

www.agilent.com/fi nd/agilentdirectQuickly choose and use your test equipment solutions with confi dence.

Agilent Email Updates

Agilent Direct

www.agilent.comFor more information on Agilent Technologies’ products, applications or services, please contact your local Agilent office. The complete list is available at:www.agilent.com/fi nd/contactus

AmericasCanada (877) 894-4414 Latin America 305 269 7500United States (800) 829-4444

Asia Pacifi cAustralia 1 800 629 485China 800 810 0189Hong Kong 800 938 693India 1 800 112 929Japan 0120 (421) 345Korea 080 769 0800Malaysia 1 800 888 848Singapore 1 800 375 8100Taiwan 0800 047 866Thailand 1 800 226 008

Europe & Middle EastAustria 0820 87 44 11Belgium 32 (0) 2 404 93 40 Denmark 45 70 13 15 15Finland 358 (0) 10 855 2100France 0825 010 700* *0.125 €/minuteGermany 01805 24 6333** **0.14 €/minuteIreland 1890 924 204Israel 972-3-9288-504/544Italy 39 02 92 60 8484Netherlands 31 (0) 20 547 2111Spain 34 (91) 631 3300Sweden 0200-88 22 55Switzerland 0800 80 53 53United Kingdom 44 (0) 118 9276201Other European Countries: www.agilent.com/fi nd/contactusRevised: March 27, 2008

Product specifi cations and descriptions in this document subject to change without notice.

© Agilent Technologies, Inc. 2008

For more information about Agilent EEsof EDA, visit:

www.agilent.com/fi nd/eesof

nstewart

Text Box

Printed in USA, May 26, 2006 5989-9453EN

Documents

Dijagram Oka