High accuracy
A sticky problem that almost every engineer runs into is the need to capture a waveform at a point in a circuit that is physically inaccessible. The test-equipment industry’s answer to this problem is known as “de-embedding,” as the instrument removes the effects of fixtures and probes on the measurement.
The latest instrument that features embedding/de-embedding capability, Agilent Technologies’ 86100D DCA-X, is a wideband sampling oscilloscope that sports great flexibility in addition to high accuracy (see the figure). The scope’s analog bandwidth of 18 GHz to more than 90 GHz combines with low noise and ultra-low intrinsic jitter to make it possible to capture the nuances of a device’s or circuit’s true performance.
Among the highlights of the scope is a new front-panel layout, a new CPU (Intel Core Duo 2 at 3 GHz), a new power supply, and a new distribution board. But the feature that has the most impact on usability and functionality is the new FlexDCA graphical user interface. Coupled with the CPU, the GUI enables the integrated embedding/de-embedding functionality, which springboards from the Infiniisim feature on Agilent’s high-end Infiniium 90000 X-series scopes.
Even as the DCA-X scope enables designers to make measurements with de-embedding, it remains 100% backward compatible with all previous DCA modules and completely code-compatible with the earlier 86100C scope. The latest version offers a high-channel-count architecture with support for up to 16 parallel measurement channels (eight differential pairs).
Several hardware enhancements have been incorporated into the scope to boost usability and flexibility. For example, its mappable vertical control controls the gain/offset of any channel and/or math function. Meanwhile, a user-definable knob, another feature imported from the Infiniium 90000 X-series scopes, can be assigned to a commonly used analog control such as data rate or phase-locked loop (PLL) bandwidth. In addition, the scope sports a multipurpose button that’s also user-definable. With the press of one button, users can, for instance, save a waveform, print a report or screenshot, or run a macro, among other functions.
The key to the scope’s de-embedding functionality is an optional waveform-transformation toolset, the 86100D-SIM InfiniiSim-DCA. Its de-embedding, embedding, and virtual-probing capabilities help users characterize high-speed digital designs more thoroughly and with improved margins.
With the toolset option installed on the DCA-X mainframe, users can remove the full effect of fixtures, cables, and channels from measurements. It’s also possible to emulate a signal at the output of a cable or channel. The instrument accurately characterizes fixtures, devices, and cables, providing calibrated S-parameter files in Touchstone format.
From there, it’s a simple matter to have the instrument de-embed or embed these elements of the device under test, displaying a simulated signal that removes (or adds) the effect of the extraneous elements. After measurements are taken, the simulated signal can be displayed alongside the actual measured signal to compare results. Corrected jitter and amplitude results are also provided.
Pricing for the 86100D DCA-X scope starts at $21,500 with four-week delivery. The 86100D-SIM InfiniiSim-DCA waveform-transformation software starts at $5000 with 10-week delivery.