Why do the WFM601i and WFM601M show a slower rise time for the eye pattern display than the WFM700M and VM700T opt 1S?

问题：

答案：

The WFM700 was designed with a large bandwidth to support HD and therefore this faster response is used in SD to show the faster risetime of the SD-SDI signal. A similar high bandwidth circuit is also used in the VM700T.

The WFM 601i and WFM601M Eye display has a -3 dB bandwidth of approximately 450 MHz. This is a 20 - 80% risetime of 500 ps. This finite risetime must be considered when determining the actual risetime of the source being measured.

The actual risetime of the source being measured can be calculated using the following formula:

Tr(source) = sqrt[(Tr(measured)^2 - (0.5ns)^2]

Note: Tr(source) = the actual 20-80% risetime of the source in ns.
Tr(measured) = the 20 - 80% risetime measured on the WFM601i or WFM601M in ns.

This table shows some conversion values between measured and actual risetimes:

Meas.			Act.
640 ps			400 ps
710 ps			500 ps
780 ps			600 ps
860 ps			700 ps
900 ps			750 ps
940 ps			800 ps
1.0 ns			900 ps
1.1 ns			1.0 ns
1.2 ns			1.1 ns
1.3 ns			1.2 ns
1.4 ns			1.3 ns
1.5 ns			1.4 ns
1.6 ns			1.5 ns

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常见问题 ID 57966

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