In electronics, telecommunications and mechanics, modulation means varying some aspect of a continuous wave carrier signal with an information-bearing modulation … See more

A useful modulation signal m(t) is usually more complex than a single sine wave, as treated above. However, by the principle of Fourier decomposition, m(t) can be expressed as the sum of a set of sine waves of various frequencies, amplitudes, and phases. … See more

The RF bandwidth of an AM transmission (refer to figure 2, but only considering positive frequencies) is twice the bandwidth of the modulating (or "baseband") signal, since the upper and lower sidebands around the carrier frequency each … See more

Modulation circuit designs may be classified as low- or high-level (depending on whether they modulate in a low-power domain—followed by … See more

Amplitude modulation was used in experiments of multiplex telegraph and telephone transmission in the late 1800s. However, the practical development of this technology is … See more

The carrier wave (sine wave) of frequency fc and amplitude A is expressed by
$${\displaystyle c(t)=A\sin(2\pi f_{c}t)\,}$$.
The message signal, such as an audio signal that is used for modulating the carrier, is m(t), and has a frequency fm, much lower than fc: See more

The AM modulation index is a measure based on the ratio of the modulation excursions of the RF signal to the level of the unmodulated carrier. It is thus defined as: See more