The FFT display shows frequency based signals as generated from the FFT functions. The x-axis shows the frequency while the y-axis shows the amplitude of the different spectral components. The FFT display can show signals with logarithmic y-axis as well as linear y-axis.

The frequency plot of a signal gives you all frequency related information of the signal. Using the FFT display SBench 6 is turned into a Spectrum Analyzer like instrument. Based on the FFT plot there are several additional calculation routines available to specify the signal.

Harmonics Cursor

A special cursor mode is available for the FFT display: the harmonics cursor. Inhere the cursor is multiplied by additional cursor lines each located at one of the harmonics frequencies of the current cursor position. Using this cursor one can easily see which of the frequency lines is just a harmonics line of a carrier and which one is a spurious part having another source.

The harmonics cursor shows the normal cursor line as full line with a arrow marker at the bottom of the line. The number of harmonics is shown as dotted lines in the correct x axis position related to the current position of the main cursor. The main cursor is moved by the mouse as before. The harmonics cursor will automatically locate the position of potential harmonic frequencies related to the current cursor position.

In our example we see that the main cursor is placed directly next to full scale sine signal and two spurious parts of the frequency signal can be determined as harmonics 2 and harmonics 3 of this full scale sine signal.