Editing Spectrum analyzer (section)

=== FFT-based ===
With an FFT based spectrum analyzer, the frequency resolution is <math>\Delta\nu=1/T</math>, the inverse of the time ''T'' over which the waveform is measured and Fourier transformed.

With Fourier transform analysis in a digital spectrum analyzer, it is necessary to sample the input signal with a sampling frequency <math>\nu_s</math> that is at least twice the bandwidth of the signal, due to the [[Nyquist rate|Nyquist limit]].<ref>{{cite web|url=https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=1775376&nid=-536900125.0.00&id=1775376&pselect=SR.GENERAL|title=How do I know what is the best sampling rate to use for my measurement? - Keysight (formerly Agilent's Electronic Measurement)|website=www.keysight.com|access-date=7 May 2018|url-status=live|archive-url=https://web.archive.org/web/20180323154748/https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=1775376&nid=-536900125.0.00&id=1775376&pselect=SR.GENERAL|archive-date=23 March 2018}}</ref> A Fourier transform will then produce a spectrum containing all frequencies from zero to <math>\nu_s/2</math>. This can place considerable demands on the required [[analog-to-digital converter]] and processing power for the Fourier transform, making FFT based spectrum analyzers limited in frequency range.

[[Image:Aaronia Spectrum Analyzer Software.jpg|thumb|right|350px|Frequency spectrum of the heating up period of a switching power supply (spread spectrum) incl. [[spectrogram]] over a few minutes]]