Electronic Design

Oscilloscopes: From Simply Viewing To Complex Signal Analysis

Much has changed since LeCroy Corp. introduced its first digital oscilloscope (DSO) in 1970. Thirty-two years ago, we used our experience in designing time digitizers and integrating ADCs for particle physics to develop a 1-Gsample/s, 8-bit DSO that had a record length of 20 samples. Since then, DSOs have come a long way, mostly to keep pace with the high-speed, complex electronic signals that must be viewed and analyzed.

Recently, analysis has become increasingly important. A relatively short time ago, viewing signals on an analog oscilloscope was acceptable. Trained engineers could "eyeball" a signal on an oscilloscope screen and determine if a glitch or other anomaly was present. "Viewing technologies" were developed for digital oscilloscopes designed to replicate the look and feel of analog oscilloscopes.

As signals grew faster and more complex in shape, the need for higher-precision measurements became crucial. Very recent advances in DSOs have created a new way to handle current and future generations of product design. More types of measurements can be made, calculations can be performed faster, and the deadtime between triggers when taking measurements and conducting analysis is much shorter.

Older oscilloscope technology used mature Windows operating systems and a processor to handle the user interface, but data handling was done with a slower embedded processor. Even just calculating a few pulse parameters required large amounts of processing resources, slowing down acquisition rates and causing a substantial increase in deadtime between triggers.

New technology allows for real-time data flow at 10 Gbytes/s from the ADC to a high-speed acquisition memory. In the memory, data is converted into packets and sent through multigigabit Ethernet links, and eventually into cache memory. This technique from LeCroy is optimized for making calculations on long data arrays, and lets signals be processed between 10 to 100 times faster than previous oscilloscope technologies.

To achieve this processing speed, DSOs have had to integrate modular software architecture and advanced chip design. The architecture enables Windows 2000 to be completely integrated with the DSO data handling, measurement calculations, analysis routines, display algorithms, and I/O functions. Advanced chip designs, like SiGe amplifiers/attenuators and ADCs, and DRAM ASICs, create the environment for streaming data to be processed through the fastest PCI bus available today.

Not only does this new technology let engineers view today's high-speed complex signals in a manner unattainable with older technologies, it expands as signal speed increases. DSOs now have the flexible platform necessary to keep pace with testing needs, allowing increasingly sophisticated measurements on ever-faster signals.

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