PrecisionProbe for Bandwidths up to 33 GHz

Introduction

PrecisionProbe solves measurement challenges by allowing you to:

• Measure input impedance and response of any probe and the loss of any cable
• Quickly correct for probe and cable loss (without extra instruments such as VNA or TDR)
• Correct probing issues such as phase non-linearity, magnitude non-flatness, and see the effect of probe loading
• Quickly gain insight into the impedance/capacitance that defines your connection

The Keysight Technologies, Inc. PrecisionProbe software (N2809A) allows you to characterize and correct your measurement system quickly and accurately, up to 33 GHz of bandwidth without adding expensive equipment.

Background – PrecisionProbe

Probes and cables have inherent loss and variation. The loss at times can be substantial, or merely different enough from the nominal to cause variation in measurements. To compensate for the inherent loss, oscilloscope vendors use probe correction via DSP. The vendor uses a “golden” model and base, all compensation/correction on the single model. While this strategy solves some of the loss and variability, it also still means that if a probe’s characteristics have changed/drifted or were not close to the model to begin with, the compensation is no longer correct for the probe. There are also a myriad of probe heads to attach to probe amplifiers for maximum accuracy when every combination must be measured. The end result is that you can get unwanted inaccuracies or probe to probe variability.

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” system. Meaning that custom probes are uncorrected and inaccurate, but convenient.

You may also want to add something between the probe amplifier (such as Keysight’s 30 GHz N2803A) probe amplifier and (such as Keysight’s 30 GHz N5444A browser probe head), including a cable to add length or a switch matrix. This adds inaccuracies as the probe amplifier and browser head are compensated to the model, the newly created probe now has no model. The result is that you must except 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.

Background – PrecisionProbe (continued)

Cables pose many of the same problems as probes with cable- to-cable variability. Oscilloscope vendors now mitigate this problem with the use of de-embedding software (Keysight’s InfiniiSim N5465A software). Typically for cables, you must characterize the cable using either a TDR or a VNA. Both of these methods provide characterization and s-parameters, but take time. It is the time required that typically will mean that you will characterize only one or two cables, and use that characterization (s-parameter file) to do the measurements of every similar cable they own, causing cable-to-cable variability if the cables characteristics vary from the “golden” cable.

PrecisionProbe

PrecisionProbe can solve the problems outlined in the background information by allowing quick characterization

of your entire probe system (including cables and switches). The innovative software takes advantage of the fast “cal output” signal on the 90000 Q-Series, 90000 X-Series, and 90000A Series oscilloscopes to properly characterize cables and probes.

The software quickly (less than five minutes in most cases) and accurately characterizes the desired element in the system without adding more equipment. PrecisionProbe

• Characterizes probe input impedance
• Properly Creates Custom Probe Transfer Function
• VOut / VIn or VOut/VInc = VOut/VSrc
• Removes unwanted cable loss

Now every probe and cable in the system can have the exact same response probe to probe or cable to cable, without the inaccuraies that using one model can produce.

Custom probes can now be properly characterized and unwanted responses can be removed.

Not only does PrecisionProbe characterize the cables, it allows for immediate use on the same instrument. When combining PrecisionProbe with the 90000 Q-Series, 90000

X-Series, and 90000A Series oscilloscopes one can characterize their measuring system and be using it within five minutes without adding more complicated, expensive equipment. PrecisionProbe saves time and money while increasing accuracy.

When combining Infiniimax probes with switches between the amplifier and the probe head, PrecisionProbe allows for full correction and automation of each probes path. Full automation is then available to allow for quick swapping of the inputs.