The Components of Total Jitter

Figure 1: An overview of the jitter hierarchy,
or "jitter tree," showing the various elements
that make up total jitter

In an earlier post, we began looking at the topic of jitter, a topic of keen interest to anyone working with high-speed serial communications or the components of such a system, including transmitters, receivers, and data channels. To gain an understanding of jitter, an important first step is getting to know a little about the various categories that comprise total jitter.

Mr. Oscilloscope, Meet Mr. Computer

Figure 1: WaveStation software enables full remote
control of an oscilloscope from a Windows PC

Some things just seem made to go together, such as peanut butter and jelly, baseball and hot dogs, and Lennon and McCartney. But in the engineering world, one great combination is the oscilloscope and the PC. Both are wonderful tools but together they go places that neither can without the other.

Let's Get Serial: About Manchester Data Encoding

Figure 1: An example of Manchester coding

Founded by the Roman Empire in the first century AD, the city of Manchester, England is probably best associated today with the Manchester United Football Club of neighboring Old Trafford. But in serial-data circles, the city's name evokes Manchester line coding, or phase encoding.

Back to Basics: Jitter

Figure 1: Jitter is short-term variation
of a signal with respect to its
ideal position in time

Anyone working in applications that involve digital data, clocks, and serial data in general will eventually bump up against issues concerning jitter. Jitter is a subject of keen interest to every strata of the electronics industry. Chip makers, board integrators, system integrators, you name it: Everybody wants, and needs, to come to terms with jitter. It impacts reliability, manufacturability, and cost at all levels. And, of course, it's of keen interest to purveyors of test instruments, including us here at Teledyne LeCroy. In this first post of a projected series on jitter, we'll look at some of the tools built into modern digital oscilloscopes for jitter measurement and analysis.

Oscilloscope Basics: Trigger Holdoff

As discussed in an earlier post, triggering is the means by which we can coax an oscilloscope into showing us what we're looking for in an input signal, and indeed even simply to display it in a stable fashion. Two of the most basic triggering types are edge triggers and pattern triggers. The latter applies to mixed-signal instruments, allowing users to trigger on a logical combination of analog and digital inputs.

Back to Basics: Probes (Part IV)

Figure 1: An example of
differential probes
measuring from test
point to test point.

In three earlier posts on the basics of oscilloscope probes, we've taken a broad overview approach, looked more deeply at passive probes and inductance effects, and most recently, dug into active probes. Next up is differential probes, a different animal entirely from the foregoing types.

Back to Basics: Probes (Part III)

Figure 1: Active oscilloscope probes
sport high resistance and low
capacitance at their tips, but
terminate into a scope's 50Ω input.

In the first two installments of this series on probe basics, we examined some broad probe categories (Part I) and some of the issues that come with probe inductance (Part II). In the present installment, we'll delve a bit deeper into the topic of active probes. We'll also discuss when it's best to use passive probes and when to use active types.