Measurement Journal Issue 6

Evaluating analysis results Getting good results depends, of course, on proper conﬁguration of the EZJIT Plus software. The setup wizard is a good place to start because it can provide good initial settings for edge thresholds, CDR parameters and memory size. Additional considerations are ISI ﬁ lter parameters and RJ bandwidth settings. 2,3 Adjusting memory size is one way to optimize jitter measurements. In many cases, changing the memory size setting will produce different jitter results. This phenomenon is shown in Figures 2 and 3, which use 512 Kpts and 2 Mpts, respectively, to measure the same DUT. In such a case, the logical question is, “Which one is correct?” It is tempting to focus on the jitter numbers, but useful information is contained in each of the four displays. Comparing Figures 2 and 3, there are clear differences in the BER bathtub, RJ, PJ spectrum and composite histogram traces. An experienced engineer will also notice the broken segments in the BER bathtub window between the measured (blue) and extrapolated (gray) sections (Figure 4). These are a few examples of the useful clues for further study that are revealed by the EZJIT Plus software. Figure 4. Breaks in the BER bathtub trace exist between the measured and extrapolated sections Varying the memory size The example measurements shown in this article were made on a prototype SATA 3 Gb/s+ (SATA Revision 2.x) chipset. It was able to generate a high-frequency test pattern (HFTP) with large RJ at 1.5 Gbps. The design team was having trouble ﬁnding the true TJ and RJ values of this device while using conventional scope jitter software. Figure 2. With memory size set to 512 Kpts, TJ = 148.17 ps and RJ (rms) = 2.26 ps Initial clues were provided by the measurements shown in Figures 2 and 3. This led to follow-on measurements using the wider range of memory sizes available in the Agilent Inﬁniium 90000A digital sampling oscilloscope (DSO). Table 1 summarizes the range of memory sizes — from 512 Kpts to 32 Mpts — along with associated measurement results. These show that, as memory size increased, RJ became larger and TJ increased along with RJ. The results reveal another key point: the RJ values converged to approximately 20 ps. Figure 3. With memory size of 2 Mpts, TJ = 231.68 ps and RJ (rms) = 8.31 ps 35 Agilent Measurement Journal

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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