Keysight Technologies N2807A PrecisionProbe Advanced Kit Data Sheet 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 Advanced Kit (N2807A) includes award winning PrecisionProbe software as well as external hardware and accessories that allow you to characterize and correct your measurement system quickly and accurately to 63 GHz. 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 myriad 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. Figure 1. Probe browser with a nonstandard pitch Figure 2. Image of custom probe 2 Custom probe heads provide great convenience, but prevent Oscilloscope vendors from providing a “golden” model to correct for probe loss. The result is uncorrected and inaccurate probes in your measurement system. You may also want to add something between the probe amplifier (such as Keysight’s 30 GHz N2803A) probe amplifier and probe head (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 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 achieved in actual measurements. Figure 3. Image using LW ZIF Head 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 characteristics vary from the “golden” cable. PrecisionProbe PrecisionProbe can solve the problems outlined in the background information by allowing quick characterization 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 out to 33 GHz of bandwidth. For measurements greater than 33 GHz, the PrecisionProbe Advanced Kit includes Keysight’s N2806A Calibration Pulse Generator to accelerate the “cal output” edge to sub-7 ps rise times. This edge speed allows for PrecisionProbe characterization out to 63 GHz. 3 Figure 4. Eye diagram with no correction, notice the minimized eye margins due to fixture loss Figure 5. Same setup using PrecisionCable correction to compensate for fixture loss 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 probe’s path. Full automation is then available to allow for quick swapping of the inputs. 4 PrecisionProbe Correction Two methods exist for correcting probe responses, Vout/Vin and Vout/Vsource Vout/Vin Correction Vout/Vin characterizes the output of the probe as a function of the input at the probe tips. Defining the response this way allows you to evaluate the probe’s accuracy in reproducing the actual signal present in your system with the probe attached. This correction is known as Vout/Vin, which is what you’d see with a real band limited probe that has finite input impedance. PrecisionProbe corrects the “Vout/Vin” response to be flat with frequency and phase to your defined bandwidth limit. It does not correct the loading effects of the probe. It should be noted that Keysight’s probe frequency response corrections are typically defined using Vout/Vin. Vout/Vsource Correction The second way to correct probes is an estimate known as Vout/Vsource, this method corrects the probe as “what would be there if the probe were not present.” There are oscilloscope and probe manufacturers that design their probes and DSP correction software to display what the waveform “would have been” in the absence of the probe. One drawback of defining the probe’s response in this manner is that if the probe’s loading causes your circuit to lose some timing or amplitude margin, you probably want to know that when you make a measurement. Vout/Vsource compensation will hide these effects from you. PrecisionProbe also gives you the freedom to choose this method of correction, which can be effective if probing at the transmitter. Figure 6. A probe that has perfect transfer function shows an exact copy of a signal at the input. A probe that has a perfect system response shows the signal at the input of probe boosted by the estimate amount of loading due to the probe. 5 Figure 7. Example of frequency response correction of a cable. The 3dB down point moved from 21 GHz to 62 GHz. S21 Insertion Loss Correction Note: This measurement does require access to both ends of the fixture or cable, similar to methods such as VNA and TDR. Figure 8. PrecisionProbe corrects phase non-linearities, notice the new flat phase. 6 PrecisionCable can be used to remove insertion loss caused by cables or fixtures. Previously the only way to do this analysis was to characterize the cable using simulation, TDR, or a VNA. All of these methods can be accurate and can yield the desired results. You would then take the newly created s-parameter file to the oscilloscope and use the de-embedding software to remove the insertion loss of the fixture or cable. While this method works, it requires extra equipment and effort. PrecisionCable allows for this characterization to be done inside of the same oscilloscope that the measurements will be taken. Characterizing the cables and fixtures takes less than five minutes in many cases which saves significant time. Analysis Tools PrecisionProbe provides many tools to allow you to know exactly what has been characterized and what parameters have been improved by the innovative software. PrecisionProbe Wizard PrecisionProbe provides an easy to follow guide with its wizard. The wizard takes you step by step through the set up of the software and ensures that your measurements are taken with the highest signal integrity. Figure 9. Starting the PrecisionProbe wizard Probe Correction To maximize margins it is important to correct each probe identically and to ensure the correction method is the same. The Probe Correction menu allows you to change between Vout/Vin and Vout/Vsource. PrecisionProbe also allows for the source impedance via s-parameter file or an estimate. This is important when measuring Vout/Vsource to ensure a high level of accuracy as assuming an ideal 50 ohm environment can cause unwanted errors. Figure 10. Choosing the probe correction that you need Bandwidth Control Software such as PrecisionProbe can amplify high frequency noise when correcting for the loss of a probe or cable. The high frequency noise can then cause unwanted noise and inaccuracies. Bandwidth control allows you to remove unwanted high frequency noise by providing a filter. PrecisionProbe also provides the ability to control the amount of gain that is applied to the signal. You can increase the amount of boosting which improves risetimes but also increases noise, or you can decrease the amount of boosting which decreases noise but degrades rise times. Figure 11. Use bandwidth control to maximize margins 7 Understanding the Analysis Charts PrecisionProbe comes with many analysis charts that make understanding the characterization and correction very easy and provide insight that is unique to Keysight oscilloscopes. The Summary Chart The summary chart shows the frequency response of the corrected probe or Vout (notice how flat the response is). The chart also shows the transfer function (TF) that is applied to the signal. Figure 12. The summary chart Probe Input Impedance Knowing the impedance profile of the probe allows you to estimate the loading of the probe system. PrecisionProbe allows for you to characterize the impedance profile, along with quickly determining the capacitance, impedance and inductance. Markers allow for easy viewing of the capacitance and inductance at each frequency. Figure 13. PrecisionProbe properly characterizes a 2 pF capacitor 8 Probe Correction Filter The probe correction filter simply shows the filter that is being applied to adjust for the probe. This filter is designed to ensure the signal stays perfectly flat. Figure 14. Probe correction summary Highlights Keysight N2806A Calibration Pulse Generator Included hardware in the N2807A PrecisionProbe Advance Kit – Sub-7 ps fall time & sub-9 ps rise time give you frequency content beyond 63 GHz for your high bandwidth applications. – Fully differential output allows you to utilize both the rising and falling edges simultaneously, perfect for differential step response and TDR. – Output rep rates up to 45 GHz – buffer any serial data stream to accelerate edge speed to sub-9 ps and eliminate amplitude variations due to ISI. – Features a step response with the lowest noise and closest to ideal spectral content available, critical for demanding calibration and metrology applications. – Trigger on internal or externally sourced signals. 9 Conclusion Using PrecisionProbe provides the highest level of accuracy without requiring additional equipment. PrecisionProbe will help with accuracy in the following ways: – – – – – – Characterize the impedance of your probe Remove probe to probe variation Remove insertion loss caused by cables Correct custom probes Correct for browser variability caused by span and length variation Correct for solutions such as switch matrices The N2807A PrecisionProbe Advanced Kit provides the same award winning software and features as the original PrecisionProbe (N2809A). While the original PrecisionProbe was limited to a maximum of 33 GHz characterization bandwidth, PrecisionProbe Advanced extends this functionality out to 63 GHz by including Keysight’s N2806A Calibration Pulse Generator. Figure 15. Real time eye with uncorrected cable loss Figure 16. Real time eye with corrected cable using PrecisionProbe 10 Ordering information DSO/DSA 90000 Q-Series Option Stand-alone DSOX90000Q-827 N2807A DSO/DSA 90000 X-Series None N2807A DSO/DSA 90000A Series None N2807A Included equipment Part number Quantity Description N2812A 1 High Performance Input Cable – 2.9 MM – 1 m N2814A 1 Ultra high bandwidth input cable – 1.85 mm – 1 m N2806A 1 Calibration Pulse Generator, sub-7 ps edges PrecisionProbe software license 1 Recommended accessories Part number Description N2812A High performance input cable – 2.9 mm – 1 m N2814A Ultra high bandwidth input cable – 1.85 mm – 1 m N5443A Performance veriication and deskew ixture (probes) N2787A 3-D probes positioner N5520B Connector assembly – 1.85 mm female to female 5061-5311 Connector assembly – 3.5 mm female to female 11 Detailed Speciications for Included Hardware: N2806A Calibration Pulse Generator Output Parameters Waveform Step pulse, square wave, or drive to DC high or low Rise time 10% - 90% (Warranted) < 10 ps Rise time 10% - 90% (Typical) < 9 ps Fall time 10% - 90% (Warranted) < 8 ps Fall time 10% - 90% (Typical) < 7 ps Maximum Square Wave Rep Rate 45 GHz Output VHI 0V Output VLO -500 mV / -1.0 V Selectable Step Duration Unlimited time hold at high or low voltage Overshoot 10%, typical RF Output Impedances 50 Ohms RF Trigger Input Parameters Maximum input voltage ± 700 mV Minimum Input dV/dt >2 V/ns Trigger Threshold 0 V / -250 mV selectable Input Impedance 50 Ohms Max Rep Rate 45 GHz Square Wave Trigger Output (Control Module) Parameters Output Impedance 50 Ohms Amplitude 1.0 Vp-p (± 500 mV) Waveform Square wave Fequency 4 MHz General Speciications Temperature Operating: 5 C to 40 C, Non-operating: -40 C to 65 C Humidity Operating: up to 95% relative humidity (non-condensing) at 40 C, Non-operating: up to 90% relative humidity at 65 C. Altitude Operating: up to 3,000 meters (9,000 feet), Non-operating: up to 15,300 meters (50,000 feet) Vibration Power 100 - 240 VAC at 50/60 Hz: maximum input power 25 Watts Weight Dimensions Remote Head: 3.3 x 2.2 x 0.94 inches, Control Module: 2.16 x 5.4 x 7.75 inches Safety ESD HBM 12 >2 kV on remote head RF input , 400 V on remote head RF outputs Keysight Technologies Oscilloscopes Multiple form factors from 20 MHz to > 90 GHz | Industry leading specs | Powerful applications 13 14 | Keysight | N2807A PrecisionProbe Advanced Kit - Data Sheet myKeysight www.keysight.com/find/mykeysight A personalized view into the information most relevant to you. www.axiestandard.org AdvancedTCA® Extensions for Instrumentation and Test (AXIe) is an open standard that extends the AdvancedTCA for general purpose and semiconductor test. 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