Measurement Journal Issue 6

Performing further analysis For these measurements, CDR bandwidth was set to 1.55 MHz and, as a consequence, some parts of the jitter below 1.55 MHz in the RJ, PJ spectrum were removed. However, when CDR is set to a constant frequency, an analysis of the SATA DUT’s signal produces a complete RJ, PJ spectrum. As seen in Figure 10, the jitter spectrum shows that the energy is strong in the low-frequency range, but it is inversely proportional to an increase in frequency. This effect is typically called ﬂicker noise. Flicker noise normally happens inside a chipset’s phaselocked loop (PLL) circuit, and this is typically related to either intrinsic material characteristics or the PLL design itself. Figure 8. The J-BERT measured a TJ of 251 ps at BER level of 1.136x10-9 Figure 10. With constant-frequency CDR, the RJ, PJ spectrum exhibits a large ﬂicker noise effect (TJ is 509.19 ps) Figure 9. With memory size set to 32 Mpts, the EZJIT Plus software measured a TJ of 259.67 ps at a BER level of 10-9 Because the CDR characteristics of these two instruments aren’t exactly the same, it is reasonable that the results will have minor differences. Referring back to Figures 8 and 9, the J-BERT direct bathtub scan and the Inﬁniium oscilloscope agree within 3 percent when the EZJIT Plus TJ measurement has a memory size of 16 or 32 Mpts. Whenever the 3 Gb/s+ SATA device produced strong ﬂicker noise, it showed up as large spectrum density in the lowfrequency range (low-frequency RJ). When making measurements on this type of device, it is better to choose larger memory size in the scope, enabling the software algorithm to correctly calculate RJ (rms). There is one caveat: Choosing an unnecessarily large memory size causes a longer measurement time and will provide only a minimal improvement in jitter accuracy. Agilent Measurement Journal 38

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

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.