Tektronix P7313SMA, Техническое описание

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Operating Basics
Checking Cable Skew
The time-delay difference (skew) between the ends of the matched-delay SMA cable pair supplied with the probe is typically
less than 1 ps. If you use a pair of matched, high-quality, low-loss cables other than those supplied with the probe, you can
bring the skew to within 1 ps by using a pair of phase adjusters. (See page 48,
Optional Accessories .)
You can measure the skew of a pair of matched cables by connecting the cables to a Tektronix 80E08 or 80E10 Sampling
Head, con
fi gured for a TDR output. (See Figure 11.)
1. Turn on the equipment and let it warm up for 20 minutes. Do not connect the cables to the sampling head yet.
2. Do a system compensation for the TDR module, and then verify the skew of the two outputs with the TDR outputs
open, using a common-mode TDR drive.
Skew between the two outputs can be compensated with the TDR module deskew control. Refer to your sampling head or
oscilloscope manual for instructions.
3. Connect the matched cable pair to the TDR outputs.
Figure 11: Checking skew between inputs
4. The measured skew of the matched cable pair that are supplied with the probe should be less than 1 ps. User-supplied
cables may not be nearly as accurate, and may require some trial-and-error testing to select an optimally-matched pair.
Adjust the horizontal scale to locate the pulse (to account for the cable delay; it is approximately 4.5 ns for the cable set
supplied with the probe). If you use the system cursors, be aware that the displayed time is the round-trip time (step and
re
fl ection). You need to divide the displayed time difference by 2 to derive the actual skew.
If you need to minimize the skew of a pair of cables not supplied with the probe, continue with Adjusting Cable Skew . (See
page 19, Adjusting Cable Skew .)
18 P7313SMA Technical Reference