Fast Fourier Transforms

“Fast Fourier Transforms” explores the capabilities and benefits of the Fast Fourier Transform (FFT) feature in the next-generation Infiniium EXR, MXR, and UXR-series oscilloscopes. This feature is essential for analyzing signal frequency content, ensuring signal integrity, and optimizing serial bus performance.

The lesson introduces FFT as a standard math function in Infiniium oscilloscopes. FFTs allow users to quickly and easily view the frequency contents of their signals. To activate this feature, users can navigate to the “Math - New FFT” menu and select the desired channel. This action generates a new plot with scales and controls similar to those of a spectrum analyzer. The vertical scale is controlled at the top with a scale and reference level, while horizontal controls are located at the bottom.

In the demonstration, a one-kilohertz square wave with noise is analyzed. By adjusting the stop frequency to 100 kilohertz, the fundamental frequency and its harmonics become visible on the screen, along with an outlier signal. The built-in markers can identify the outlier’s frequency and power, or users can utilize the automatic peak detection feature by selecting “Mark peaks.” The default setting identifies the five most powerful peaks, but users can adjust the definitions and number of peaks in the FFT settings. The settings dialogue also allows adjustments to other features such as the window, detector type, and scales.

The video highlights the ability to add additional math functions on top of the FFT, up to 16 in total. This capability enables users to plot the FFT’s average, maximum, or minimum values. Additionally, a wide variety of automatic measurements can be performed on the FFT waveform, including channel power and occupied bandwidth.

Overall, the lesson offers insights into the practical applications and benefits of FFT in modern oscilloscopes. By leveraging FFT, engineers can ensure signal integrity and optimize the performance of serial buses. The Infiniium EXR, MXR, and UXR-series oscilloscopes provide powerful tools for frequency analysis, making them invaluable for engineers working with complex signals.