Communications Toolbox

Modulation Features of the Toolbox

The available methods of modulation depend on whether the input signal is analog or digital. The figures below show the modulation techniques that the Communications Toolbox supports for analog and digital signals, respectively. As the figures suggest, some categories of techniques include named special cases.

Baseband Versus Passband Simulation

For a given modulation technique, two ways to simulate modulation techniques are called baseband and passband. Baseband simulation, also known as the lowpass equivalent method, requires less computation. This toolbox supports both baseband and passband simulation. Because baseband simulation is more prevalent, this guide focuses more on baseband simulation.

Note    To use this toolbox for passband simulation, see the reference pages for the functions amod, ademod, dmod, and ddemod.

Supported Modulation Tasks

Functions in the toolbox can accomplish these tasks:

• Modulate a signal using one of the techniques shown in the figures above
• Demodulate a signal using one of the techniques shown in the figures above
• Map a digital signal to an analog signal, before modulation
• Demap an analog signal to a digital signal, after demodulation
• Map, demap, and plot constellations for QASK modulation

The modulation and demodulation functions also let you control such features as the initial phase of the modulated signal, post-demodulation filtering, and the decision timing for digital demodulation.

Modulation

Modulation Terminology