Spectrum of a Modulated Sinusoid

The spectrum example is defined by the following block diagram:

The model consists of two signal sources, each of which generates a sine wave, and a noise source. The frequencies of the sine waves and the standard deviation of the noise are controlled by model parameters accessible in the execution applet. The Expression actor combines the three signals using an expression that you can view by right clicking and selecting "Edit Parameters". The Spectrum actor is a hierarchical model that calculates a periodogram spectral estimate (the magnitude of the discrete Fourier transform of the observed data). The Display actor shows the spectrum estimate (in decibels).