Multitone Generation

Except for the sine wave, the common test signals do not allow full control over their spectral content. For example, the harmonic components of a square wave are fixed in frequency, phase, and amplitude relative to the fundamental. However, you can generate multitone signals with a specific amplitude and phase for each individual frequency component.

A multitone signal is the superposition of several sine waves or tones, each with a distinct amplitude, phase, and frequency. A multitone signal is typically created so that an integer number of cycles of each individual tone are contained in the signal. If an FFT of the entire multitone signal is computed, each of the tones falls exactly onto a single frequency bin, which means no spectral spread or leakage occurs.

Multitone signals are a part of many test specifications and allow the fast and efficient stimulus of a system across an arbitrary band of frequencies. Multitone test signals are used to determine the frequency response of a device and with appropriate selection of frequencies, also can be used to measure such quantities as intermodulation distortion.