Measurement Journal Issue 6

T The Beijing Summer Olympic Games were viewable through unprecedented amounts of television- and Internet-based coverage, including over 3,600 hours delivered by U.S. network NBC. Capturing, storing and delivering the seemingly countless hours of events and ceremonies required terabytes worth of digital storage devices, many of which were Serial Advanced Technology Attachment (SATA) hard disc drives. The ability to move ever-larger data files requires fast, dependable data transfers. To meet these demands in media servers, desktop PCs and other applications, data rates are increasing for most serial-bus standards and designs. For engineers designing serial chipsets and characterizing or debugging serial devices, a technique called jitter analysis is becoming an increasingly important and useful tool. The reason is simple: As serial data rates increase, the timing budget for jitter decreases. For example, the third-generation SATA interface (SATA Revision 3.x) will provide a data rate of up to 6 Gbps. In the “SATA 6 Gb/s+” draft standard, the total jitter (TJ) speciﬁcation is 0.37 unit intervals (UI) where 1 UI is 166.6 ps. Thus, designers must manage all contributions to jitter to ensure that TJ doesn’t exceed 61.64 ps (0.37x166.6). One alternative is Agilent’s EZJIT Plus jitter-analysis software, which runs in an oscilloscope for TJ estimation and separation of random and deterministic jitter (RJ/DJ). This solution is widely accepted and is being applied to advanced applications such as PCI Express, HDMI and DisplayPort. With its jitteranalysis functionality, EZJIT Plus makes it easy for engineers to analyze jitter components such as periodic jitter (PJ), inter-symbol interference (ISI) and duty-cycle distortion (DCD). The EZJIT Plus software also provides a friendly user interface with single-display views of multiple windows (Figure 1). Each window provides multiple perspectives of a device under test (DUT) and its performance.1 Measuring total jitter Total jitter is the most important indicator of jitter performance in a device at a given bit-error-rate level (e.g., 10-12). In principle, TJ should be measured directly with a bit-error-rate tester (BERT) because it is the most accurate method. However, when performing a bit-error-ratio (BER) measurement at a low level (e.g., 10-12) it takes a long time to perform a typical bathtub scan. Even with enhanced algorithms such as fast total jitter (FTJ) that shorten the measurement time, designers must set up clock data recovery (CDR) parameters that ensure compliance with an individual application’s jitter transfer function. Figure 1. Four-window display includes composite histogram, data-dependent jitter (DDJ) versus bit, BER bathtub plot, and RJ, PJ spectrum Agilent Measurement Journal 34

Table of Contents Feed for the Digital Edition of Measurement Journal Issue 6

Measurement Journal Issue 6 Using a Few Words to Convey a Deeply-Held Spirit Charting a Unique Path to Technology Innovation Contents Announcing First Commercial GC/MS Metabolites Library Assessing Nonlinear Behavior Testing Combines Form and Function Testing Multiplay Networks Higher Sensitivity LC/MS Easing Military Radio Test Stepping Up Calibration Accuracy Increasing Spectrum Analyzer Bandwidth 3GPP Tool Supports TS 36 Standards The Olympic Story Spotlights Agilent's Continuing Contribution to Technology Innovation Ensuring a Level Playing Field in Competitive Sports GPS: Coming of Age Resolving Design Issues in HSPA Mobile Devices Achieving Accurate Results with Oscilloscope-Based Jitter-Analysis Software RF Handheld Testers Guarantee Traffic Stability Under Olympic-Sized Stress Conditions Utilizing LAN-Based Instrumentation to Measure Total Harmonic Distortion in Remote Facilities IMT-Advanced: 4G Wireless Takes Shape in an Olympic Year EPO Doping: A Speed Engine, Turbo-Charged by Chemistry

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