Spans, Spurs, and Spectral Analysis: Performing FFT Calculations and Measurements on a DSO

Some digital sampling oscilloscopes (DSOs) can perform frequency analysis using an on-board FFT (Fast-Fourier Transform) calculation applied to a time-based acquisition, which provides immediate measurement information for automated test without introducing the need for additional data download and processing. This paper will provide an overview of FFT basics, associated measurements, and window selection, and discuss considerations when configuring the time-based acquisition, including how points and sample rate influence the FFT characteristics.