Spectrum and Bandwidth

Spectrum

A frequency spectrum is the range of all possible frequencies of electromagnetic radiation. A full continuous spectrum, for example, includes radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma rays.

Sometimes this can be confusing in the context of a signal, as its spectrum contains the frequencies of complex sinusoids that sum up in the time domain to form that signal. For this purpose, we use the term bandwidth.

Bandwidth

The bandwidth of a signal is the range of frequencies of complex sinusoids present in that signal.

We can say that the bandwidth is the difference between the highest frequency ($F_H$ ...