# Amplitude spectrum vs frequency spectrum

1. Apr 22, 2017

### whatphysics

What is the difference between amplitude spectrum and frequency spectrum? In signals and systems.

2. Apr 22, 2017

I THINK, not super sure, that frequency spectrum can be split up as an amplitude spectrum and a phase spectrum.
A frequency spectrum is a spectrum of complex numbers containing both amplitude (magnitude) and phase.

3. Apr 22, 2017

### tech99

I think a frequency spectrum is a plot of frequency versus power (usually in decibels, in engineering). The power will be measured in a narrow passband which is swept across the spectrum,.
An amplitude spectrum is perhaps the same thing where amplitude, not power, is displayed.
Amplitude is proportional to the square root of power.

4. Apr 23, 2017

### Tom.G

Spectrum is something that can vary across a continuous range, or continuim.
See: https://en.wikipedia.org/wiki/Spectrum
A strict interpretation of the WIKI article would imply that "Frequency Spectrum" is a redundant phrase. Frequency Spectrum is, however, a commonly used engineering term for power versus frequency.

Following along with the above, is a WIKI article on Spectral Density: https://en.wikipedia.org/wiki/Spectral_density

Combining the concepts in the above article seems to lead to an "Amplitude Spectrum" being an 'amplitude versus time' relationship.

(Since the terms you asked about are rather ill-defined in general usage, there is still plenty of room for discussion/opinion/arguement!)