Hal,

We have seen the same trend. The fact of the matter is that the frequency for
TDR test is establshed by the length of the test trace. The shorter the
trace, the higher the frequency required. Because of the need for high
resolution, most TDR systems employ the sampling principle to achieve the
high system bandwidth required by short length traces. A lower system
bandwidth (less than 20 Ghz) limits the capability of accurately measuring
short length traces.

We send a copy of the test results, which includes the resulting frequency
under test, to our customers, with a description of the measurement technique
and process. To date, our reply has been sufficient.

Gary Ferrari
Tech Circuits