D9110DMBA De-embedding Software for Infiniium Oscilloscopes

D9010DMBA

De-embedding software for Infiniium oscilloscopes

Introduction

This package includes PrecisionProbe and InfiniiSim Basic, two tools designed to de-embed the effect of cables and fixtures from measurements. PrecisionProbe allows you to characterize the response of a probe or cable; InfiniiSim lets you model out probes or cables from a measurement. It is available on all Infiniium oscilloscopes.

Background: Why De-embed?

A measurement system is only as good as its weakest link. Users spend thousands of dollars on test and measurement equipment, including oscilloscopes, but then ignore the weakest element in their link, the cable. Oscilloscope vendors now provide methods to strengthen the weak link with the use of deembedding software. However, de-embedding software requires specific characterization of the cable and the creation of an S-parameter file. To get the correct characterization, you must characterize the cable using either a TDR or a VNA. Both methods provide characterization and S-parameters but require time, instrument knowledge, and more investment on test and measurement equipment.

It is the time, knowledge, and additional equipment that causes us to simply choose to ignore cable loss, and measurements taken by the oscilloscope now may be measuring the weakest link (the cable) and not the device you wish to measure as cable loss can dominate a measurement. At best you may choose to characterize only one or two cables and use that characterization (s-parameter file) to compensate for of every similar cable you own, causing the magnification of cable-to-cable variability as the cables characteristics vary from the “golden” cable.

Probes and cables are inherently lossy and rarely identical in their characteristics. The loss at times can be substantial, or enough from an ideal flat frequency response to cause variation in measurements and the loss of valuable margins. To compensate for the inherent loss, oscilloscope vendors use DSP correction to compensate for loss caused by probes. If a probe’s characteristics have changed/drifted or were not close to the model to begin with, the compensation may cause the probe to make worse measurements.

You also use custom probes and probe heads. While this provides great convenience for you, it means that the oscilloscope vendor no longer can even provide a “golden” compensation for your probe configuration. As a result, custom probes are uncorrected and inaccurate, but convenient.

You may also want to add something between the probe amplifier and probe head, including a cable to add length or a switch matrix. Adding a new element in the probe system adds inaccuracies as the probe amplifier and browser head are compensated to the model, but the newly created probe system now has no model. The result is that you must accept the inaccuracies that have been added or try to characterize the additional element in the probe link. While accepting both of these trade-offs can be sufficient, it is time consuming to evaluate the element every time and not characterizing the element causes loss of margins (including higher jitter, smaller eyes, and slower rise times). This can also be the cause of differences between numbers measured in simulation and the number actually achieved in actual measurements.

Product Overview

This software option contains two key parts: PrecisionProbe and InfiniiSim Basic.

PrecisionProbe lets you characterize any cables, probes or fixtures in your test path. Using the software tool and some fixture hardware, you can measure the transfer function of a probe or cable, thus removing the effects from your measurement results on the oscilloscope.

InfiniiSim Basic takes S-parameters of a single cable or fixture element, defined by you, and can remove the impact of it from your measurement results, giving you larger eye openings and more accurate measurements. These S-parameters may be measured directly using TDR or a VNA.

There are some reasons this package may not be for you. You require InfiniiSim Advanced, part of the D90x0ASIA software package for Infiniium oscilloscopes if you need the following capabilities:

• If you need to relocate your measurement plane (e.g. to a place in your DUT that can’t be directly probed).
• If you need to remove or simulate more than one element in your test setup.
• If you need to remove the loading effects of your probe, cable, or fixture from your measurement.

Please note that this is only a software package. For PrecisionProbe accessories and fixtures, please consider the hardware accessories outlined in the PrecisionProbe section.