A perspective for analyzing signals where the X-axis represents frequency and the Y-axis represents amplitude or phase. Instead of viewing a waveform as a squiggly line changing over time, engineers view it as a collection of individual sine waves at specific frequencies. Spectrum analyzers natively display signals in the frequency domain, making it easy to spot harmonics, interference, and bandwidth limits.
The scope trace looks like pure noise in the time domain, but if you switch to the frequency domain you'll see a massive spike at 2.4 gigahertz.
Related terms
Fourier transform
A mathematical operation that breaks a time-based signal into its constituent frequencies.
Signal processing
The mathematical manipulation of physical data streams to filter, compress, or extract information.
RBW
The filter width setting on a spectrum analyzer determines the smallest frequency separation between two signals that can be distinctly resolved.