5. Math Functions
Figure 5.2. First derivative trace (yellow, bottom).
5.2.1. Second and Higher Order Derivative Traces
The 1st Derivative function can be applied to First Derivative traces to create second (and higher)
order derivatives.
5.3. Fast Fourier Transform (FFT) Traces
The CT100B can calculate FFT frequency-domain information from live and scanned TDR traces.
FFT traces can be used to show the frequency-domain content of a trace or portion of a trace
between cursors, and comparisons of FFT traces can be used to demonstrate differences and/or
changes in frequency content, such as between different types of connectors or cable faults. To
create an FFT trace, use the following procedure:
1. Select the live trace with the SELECT button.
2. Use the CURSOR button and the HORIZONTAL POSITION knob to set the boundaries for
the FFT with a cursor at either end.
3. Press the SCAN button, and then select Math → FFT Tools.
4. Select Apply FFT. The CT100B will now take a high-resolution scan of the live trace between
the cursors, and then convert the scan into an FFT plot. See Figure 5.3.
CT100B TDR Cable Analyzers Operator’s Manual 79
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