Analysis Software for DSA8300 Sampling Oscilloscopes

Features & Benefits

• Jitter, noise, and BER analysis of high-speed serial data rates from <1 Gb/s to 60 Gb/s provides insight into precise causes of eye closure
• Analysis of bounded uncorrelated jitter (BUJ) and noise handles the effects of crosstalk, avoids undue inflation of the RJ and TJ
• FFE/DFE equalization of the signal opens the eye diagram for measurements – view the signal the way the receiver comparator views it
• Channel emulation from TDR waveforms or from S-parameters inserts virtual channel: Observe the signal as it will look at the end of the interconnect, even while capturing the transmitter waveform only
• Separation of both jitter and noise provides highly accurate extrapolation of BER and eye contour
• J2 and J9 measurements, DDPWS measurement and plot in support of IEEE 802.3ba 100 GbE
• Unmatched measurement system fidelity with ultra-low jitter floor for accurate and repeatable measurement results
• SSC support: Analysis of systems with spread spectrum clocking, with profile and frequency
• Fixture de-embed removes the signal distortion caused by the measurement fixture
• Channel emulation recalculation: With just one transmitter acquisition, view the link performance for a number of emulated channels
• Over 30 dB of channel loss can be equalized, supporting advanced backplane standards
• Store and recall dataset: Save transmitter dataset, then recall this dataset later and continue the data experiments

Applications

• Characterize jitter, noise, and BER performance of high-speed serial designs from 1 Gb/s to 60 Gb/s data rates
• Characterize advanced links using FFE/DFE equalization, and with DDPWS measurements
• Link budgeting and “what-if” analysis with emulation of a range of channels by using just one transmitter measurement
• Acquire precise waveform shape for simulations or other processing; rely on acquisition with state-of-the-art resolution, jitter, noise, and with fixture de-embedding support
• Characterize jitter, noise and BER performance of multi-gigabit standards such as Fibre Channel, OIF CEI, XFP, UXPi, IEEE 802.3 Ethernet, physical layer, XAUI, nAUI, Rapid I/O, XFI, SFP+, InfiniBand, and other electrical or optical standards
• Design validation and characterization of next-generation high-speed serial data computer and communications components and systems
• Transmitter measurement: Evaluate transmitter equalization (pre-emphasis/de-emphasis) from tap values of an FFE equalizer equalizing the transmitter-equalized waveform
• Serial data link design and evaluation: Consider the alternatives for equalization with quick adjustments of the built-in flexible equalizer using a large number of taps and automatic tap weight calculation
• Save complete waveform dataset information for future reuse. Then recall the dataset for experiments with a new physical layer

Jitter, Noise, BER, and Serial Data Link Analysis Software for DSA8300 and 8000 Series Tektronix Sampling Oscilloscopes

High-speed serial data link measurements and analysis are supported with three software solutions: 80SJARB, 80SJNB Essentials, and 80SJNB Advanced.

80SJARB is a basic jitter measurement tool capable of measuring jitter on any waveform – random or repetitive. The simplicity of acquisition limits the amount of analysis possible so only the simplest decomposition can be used; repeatability is pattern dependent.

80SJNB Essentials offers complete analysis of jitter, noise, and BER, with decomposition of components for clear understanding of a signal’s problems and margins. The acquisition methodology requires a repetitive pattern. Both accuracy and repeatability are improved relative to 80SJARB since the tool has access to the complete signal pattern. New in the latest release is capability for comprehensively handling bounded uncorrelated jitter (BUJ, etc.) and noise.

80SJNB Advanced adds features to 80SJNB Essentials for Serial Data Link Analysis (SDLA) – de-embedding*¹ of fixture, channel emulation, FFE/DFE equalization, pre-emphasis/de-emphasis.

Modern Serial Data Link Designs

Acceleration of signaling speeds creates a number of challenges for design and test. The designs are evolving to address these challenges with equalization techniques in the receiver, pre-emphasis, or de-emphasis in the transmitter; with dedicated fixtures for capturing the signal at test point; and with complex compliance verification procedures.

80SJNB Offers the Tools

The advanced techniques employed by the designs call for advanced tools in the measurement solutions. The concerns begin with acquisition: capturing the data signal through physical fixture distorts signal shape; 80SJNB provides you with a fixture de-embedding*¹ feature which allows you to remove the effects of the fixture from the measurement. The accuracy improvement might well mean the difference between a passing design and a failing one, because the impact of the fixtures on the signal fidelity today is large.

And what is the transmitter signal shape you are capturing? The signal from the transmitter is no longer a simple NRZ square-wave pattern. Transmitter designers alleviate high-frequency loss in the media with transmitter equalization features, for example with pre-emphasis or de-emphasis of the transmitter waveform. Correspondingly, transmitter signals today need to be evaluated for this transmitter equalization; your 80SJNB quickly provides equalizing tap weight results to give you insight into the quality of your transmitter for both single- and multi-tap transmitter equalization designs.

*¹ The tool for de-embedding filter creation is available through your Tektronix sales office free of charge.

*² Dual Dirac.

Measure Jitter and Noise

80SJNB revolutionized jitter analysis by adding noise analysis, critical to noise- and eye-closure-limited high-speed designs. Complete characterization of both jitter and noise then allowed 80SJNB to also offer capability new for oscilloscopes – BER contours, found on BERT instruments like the Tektronix BERTScope Series.

The latest version of 80SJNB offers another new feature: analysis that is aware of bounded uncorrelated disturbers (BUJ etc.). Bounded uncorrelated disturbers are a growing problem in fast, densely packed designs at 8 Gb/s and above, where they arise mostly from increased crosstalk. In older jitter and noise analysis tools they are typically mistaken for random, unbound components; classifying these components as unbound leads to inappropriate increase in random component breakdown (RJ) and total (TJ, TN) result. 80SJNB answers the challenge with a jitter and noise breakdown extended to properly classify the bounded uncorrelated disturbers in their own category, increasing the accuracy of the jitter/noise result.

Uniquely amongst jitter tools, 80SJNB breaks down the contribution of noise to jitter with RJ(v) and PJ(v). The breakdown quickly pinpoints the cause of jitter problems.

Beyond Measurements at Transmitter

An important part of today’s evaluation of serial data links is the complicated interaction between the shape of the measured waveform and the complex behavior of the interconnect channel. It is no longer possible to assume that if transmitter output meets the eye diagram mask it will work against all channels up to a given loss. Instead, advanced link test methods acquire the true transmitter waveform shape, and test against several corner-case channels.

Is the solution of emulating the channels based on their network description, for example, S-parameters? Such compliance tests are becoming a part of new standards. Now the measurement suite on your transmitter under test simply involves acquisition of the transmitter signal. Then you connect the captured signal to all required channels, one channel at a time – in emulation, rather than physically. This methodology is supported by 80SJNB; the candidate channels can be viewed without the need to reacquire the transmitter waveform. And unlike bare-bones evaluation scripts often used for pass/fail decisions the 80SJNB offers a rich set of views of the signal, starting with complete waveform, oversampled for high signal fidelity. And of course the complete set of 80SJNB jitter and noise measurements is available to support your analysis of what problems, if any, your device might have. At the same time the BER eye offers a view of the link performance that matters most to the end user – in terms of BER performance and its margins. At the end of the test, save the waveform description dataset for evidence or for future experiments; then recall and reanalyze whenever is needed without the need to reacquire.

Equalize, then Equalize Again

The equalization in the transmitter is one tool in the arsenal of tricks fighting the loss and dispersion in the interconnect: another one is the equalization at the receiver. Receiver equalization in most modern NRZ systems falls under either FFE (Feed Forward Equalization; also known as LFE – Linear Feedback Equalization), or DFE – Decision Feedback Equalization. A receiver equipped with equalization is capable of decoding signals which when viewed as an eye diagram are completely closed; How to measure such signals? The equalization tools in the 80SJNB can open a completely closed eye, with your own equalizer tap values, or, at a push of a button, equalization tap values on a PRBS pattern will be found for you, for either a FFE or DFE equalizer. The speed of recalculation and the ease of use allows you to easily modify system parameters, such as the number and weight of taps, or the amount of pre- or de-emphasis; you can verify the optimization of the design, or develop “what-if” scenarios.

If you design or measure devices intended for the high-volume PC market you will appreciate the addition of operation on the SSC (Spread Spectrum Clocking) – another first in the sampling oscilloscope measurements. Using the DSA8300 or DSA/TDS/CSA8200 mainframes plus the 82A04 Phase Reference module, the 80SJNB not only measures your signals under the presence of SSC, it also measures the SSC parameters.

Beyond just analysis, the 80SJNB presents the unmatched utility of separating the jitter caused by noise impairments versus its jitter-based component.

80SJNB BER

Perhaps the single most important result of serial data link test is the BER; uniquely, the 80SJNB brings you the BER eye plot. While measurements on narrow parts of the signal are now common (jitter at the crossing, noise at the cursor), 80SJNB captures the whole signal, and then truthfully presents the accumulation of all impairments. Measurement results at a different decision threshold or timing point are just a click away, as the 80SJNB always keeps the whole 3-D shape and all waveforms behind it.

Correlation

80SJNB Advanced offers a jitter-only analysis for compatibility with tools that measure jitter without considering the noise effect on bathtub closure.

Serial Data Link Analysis

Transmitter Equalization Measurements

Serial data transmitters employing pre-emphasis/de-emphasis can be evaluated and measured using the FFE equalization feature. The package can autoset the tap values on the received PRBS pattern, enabling evaluation of the value of taps that counter-equalize the transmitter pre-emphasis/de-emphasis.

Fixture Removal, Arbitrary Filter

At high speeds the test fixture often significantly distorts the acquired signal. The Advanced package supports a filter block which can be used for the fixture removal. But the processing block is flexible – not dedicated; it can perform as an arbitrary filter instead, for example for simulation of pre-emphasis/de-emphasis schemes.

Channel Emulation

The interaction between the true transmitter signal shape and the channel (interconnect) parameters is complex and not easily predictable from separate measurements. A reliable way to observe the performance of the whole serial link is by connecting the true transmitter waveform to the channel. The channel doesn’t have to be physically present: the Advanced 80SJNB package offers channel emulation based on network measurements of the channel. In this situation a transmitter signal with or without pre-emphasis/de-emphasis can be captured; the channel can be emulated through its S-parameters or time-domain network description, such as the TDR/TDT traces, and the signal at the end of the emulated channel can be measured.

The Platform

The 80SJNB Jitter, Noise, BER, and Serial Data Link Analysis runs on the Tektronix 8000 Series Sampling Oscilloscopes. This combination of state-of-the-art analysis software with the advantages of the Tektronix sampling oscilloscope mainframe, such as modular flexibility, uncompromised performance, and unmatched signal fidelity provide you with the ideal solution for next-generation high-speed serial data design validation and compliance testing.

Network Description Tool

The 80SJNB Jitter, Noise, BER, and Data Link Analysis software in some cases uses network description information, such as S-parameters in the Touchstone format. We recommend Tektronix TDR hardware and Tektronix IConnect application software for high-quality Touchstone network description data. Amongst the advantages of using Tek TDR and IConnect is the preservation of the DC values in the Touchstone matrix, which is typically lost with other measurement methods. 80SJNB will work with network description based on other measurement methods, such as VNA data; the DC measurement results will then typically have to be extrapolated in the 80SJNB.

Prerequisites

The software package is designed for use on 8000 Series Sampling Oscilloscopes, including the DSA8300 Digital Serial Analyzer Sampling Oscilloscopes and the older DSA/TDS/CSA8200*³, TDS/CSA8000B*³, and 8000*³ Digital Sampling Oscilloscopes and Communications Signal Analyzers.

The SSC (Spread Spectrum Clocking) support requires the use of a 82A04 Phase Reference module, which can only be used on the 8300 and 8200 Series instruments.

When clock recovery of a SSC (Spread Spectrum Clocking) signal is needed the CR125A or higher or 80A07 Clock Recovery Unit is recommended; the 80A05 Clock Recovery unit does not support SSC.

Jitter Analysis of Arbitrary Data

The 80SJARB jitter measurement application software for the DSA8300 and older 8000 Series addresses IEEE 802.3ba applications requiring the J2 and J9 jitter measurements. It also enables basic jitter measurements for NRZ data signals including PRBS31, random traffic, and scrambled data. This provides an entry-level jitter analysis capability with simple Dual Dirac model jitter analysis and no hardware module requirements. 80SJARB can acquire continuously in “free run” mode, delivering acquisitions and updates beyond the IEEE minimum requirement of 10,000 data points. Plots include jitter bathtub curves for both measured and extrapolated data, as well as a histogram of the acquired data.

*³ DSA8200 recommended, min. 0.5 GB DRAM recommended. Consult release notes for performance limitations on older systems.

Measurements

80SJNB, 80SJNB01Advanced Jitter Analysis

Noise Analysis Measurement

• Plots: Jitter and Noise Components Probability Distributions, Spectral Distributions, Data Dependent Jitter and Noise and DDPWS vs. Bit, Data Pattern Waveform, Bathtub Curves for Jitter and Noise, BER Probability Map, BER Contour Diagrams, Q-Eye, Probability Distribution Eye Diagrams (Data pattern can be plotted after every Signal Path (SP) processing step), SSC (Spread Spectrum Clocking) Profile
• Data Logging: Query and Export of all Numeric Results. Export of Waveforms: Raw Acquired Pattern Waveform, Correlated Pattern Waveform, Correlated Pattern Waveform after Every Signal Path Processing Step, Probability Distribution Eye Diagrams, and Bathtub Curves

80SJARBBasic Jitter Analysis of Arbitrary Data

• Free Run Mode: For continuous acquisitions and update beyond the IEEE minimum requirement of 10,000 data points
• Plots: Jitter/Eye Opening Bathtub, Histogram of Acquired Data