===Fourier Analysis of Time-Domain Simulation Data===
[[B2RF.Spice A/D]] can perform a discrete Fourier transform on the time-domain data at the end of a transient test. The Fourier data represent the spectral contents of the selected signal at a fundamental frequency and its harmonics. To calculate the Fourier transform, check the box titled "Apply Fourier" in the Transient Test's Settings dialog. Then, click the "Fourier Setup" button to open the "Fourier Transform Settings" dialog. In this dialog you can specify the "Fundamental Frequency" in Hertz. You should also indicate which voltage signal must be transformed. For that purpose, either specify the "Output Probe" from a drop-down list of voltage probes in your schematic or specify the "Output Nodes".
As an example, the figure below shows the Fourier contents of the output voltage of the Op-Amp circuit shown earlier. The results of Fourier analysis are plotted in a bar chart representing the spectral contents at the fundamental frequency and its harmonics.