In analog modulation, what are linear modulation and nonlinear modulation?

Generalized linear modulation refers to the modulation process in which the modulation parameters change linearly with the modulation signal in the modulated wave.

In a narrow sense, linear modulation refers to the modulation process of shifting the spectrum of the modulated signal to both sides of the carrier frequency to become the upper and lower sideband.

Nonlinear modulation is an implementation of modulation technology, which corresponds to linear modulation.

The essential difference between nonlinear modulation and linear modulation is that linear modulation does not change the original spectrum structure of the signal, while nonlinear modulation changes the original spectrum structure of the signal. In addition, nonlinear modulation usually occupies a wide bandwidth.

Common nonlinear modulation mainly includes:

Frequency modulation (FM), narrowband FM (such as civil walkie-talkie) and broadband FM (FM broadcasting) all belong to the category of nonlinear modulation.

Frequency shift keying (FSK) is often used in automatic control and wireless data transmission.

Phase shift keying (PSK) and differential phase shift keying (DPSK) are usually used for automatic control and wireless data transmission.