Introduction - If you have any usage issues, please Google them yourself
The transmission mode of the digital signal is divided into a base-band transmission and band-pass transmission, in practical applications, most of the channel having a band pass characteristic but can not directly transmit baseband signal. In order to make the digital signal transmitted in band communication channel, the digital baseband signal modulates the carrier must be used, so that the signal with the characteristics of the channel to match. This control carrier of the digital baseband signal, the digital baseband signal is converted into digital the Bandpass process called digital modulation. Keying method generally used to implement the digital modulation, such as the carrier' s amplitude, frequency and phase shift keying