RM and AM Spectra

Where the centre frequency was absent in RM, it is present in classic AM. The sidebands are identical.

**Figure 4:** Spectrum of amplitude modulation.
$\begin{figure}\centerline{% \input{amspec.pstex_t}}\end{figure}$

**Figure 5:** Spectrum of ring modulation.
$\begin{figure}\centerline{% \input{spec.pstex_t}}\end{figure}$

A DC offset in the modulating term therefore has the effect of including the centre frequency at an amplitude equal to the offset.

``Music 270a: Modulation'' by Tamara Smyth, Department of Music, University of California, San Diego (UCSD).