PAM4 modulation boosts throughput but adds test challenges. Part 1 of this two-part series described the evolution of the PCI Express (PCIe) standard, including the move from non-return-to-zero (NRZ) signaling in PCIe 5 to four-level pulse-amplitude modulation (PAM4) signaling in PCIe 6. What unique test challenges does PCIe 6 present? As mentioned in Part 1, […]
What is PCIe gen 6 and how do I test it? (Part 1)
PAM4 modulation boosts throughput but adds test challenges. The Peripheral Component Interface (PCI) emerged in the 1990s as a parallel bus for connecting computer mainboards and peripheral devices. In 2003, a serial version called PCI Express (PCIe) debuted, with generation 1 offering a transfer rate of 2.5 GT/s. Over the past 20 years, successive generations […]
That Maxwell book that was returned to a library 115 years late: what’s it about? Part 2
Work on resistance measurement, described in An Elementary Treatise on Electricity, helped pave the way to successful trans-Atlantic telegraphy. In Part 1, I discussed An Elementary Treatise on Electricity by James Clerk Maxwell. One volume made national news earlier this summer when it was returned to New Bedford, Mass. Free Public Library 115 years overdue. […]
How does a thermocouple work, and do I really need an ice bath (part 2 of 2)?
Modern thermocouple instruments automate the cold-junction-compensation process. Part 1 of this two-part series introduced thermocouple cold-junction compensation (CJC). This part will elaborate on the concept. Table 1, presented in part 1 and repeated here, lists a subset of the NIST voltage and temperature data for the type T thermocouple. Table 1. Type T thermocouple temperatures […]
That Maxwell book that was returned to a library 115 years late: what’s it about? (Part 1)
Published in 1881, An Elementary Treatise on Electricity evolved from notes Maxwell had written in preparation for lectures on electricity at the Cavendish Laboratory. In June 2023, the national media carried a story about a book 115 years overdue that was returned to the Free Public Library in New Bedford, Mass. The book turned out […]
How does a thermocouple work, and do I really need an ice bath (part 1 of 2)?
Efforts at the Bureau of Standards 110 years ago paved the way for the cold-junction-compensation technique used today. Thermocouples have long been used to make temperature measurements. They are simple, consisting of a pair of wires of dissimilar metals welded together at one end. They are rugged, operate over wide temperature ranges, and generate readily […]
What is GPIB and is it obsolete?
The bus, codified as the IEEE 488 standard, continues to find use in legacy test-system upgrades and in calibration labs. The General-Purpose Interface Bus (GPIB) began life as the Hewlett-Packard Interface Bus (HP-IB). Hewlett-Packard, whose electronic test-and-measurement business has evolved into today’s Keysight Technologies, created the interface in the 1960s to connect multiple instruments in […]
What is jitter and what can I do about it (part 2 of 2)?
Operations on acquired jitter data help quantify jitter values. Part 1 of this article described the oscilloscope eye diagram and unit interval (UI) and focused on a single ideal rising edge with 28 additional edges representing some degree of jitter (Figure 1). We determined the peak-to-peak jitter to be 15 ps, based on the edges […]
What is jitter and what can I do about it (part 1 of 2)?
Measuring and quantifying jitter are the first steps toward controlling it. Jitter is a measure of the timing performance of a digital data stream such as Ethernet, USB, PCIe, or HDMI. It defines when data transitions occur in relation to an ideal waveform. Excess jitter can lead to signal-integrity problems that result in high bit-error […]
What is de-embedding and how do I perform it (part 2)?
When testing a device in a fixture, you can use transfer scattering parameters (T-parameters) to help remove the fixture’s contribution from your measurement result.
