Frequency shift keying communication system. Digital signals are transmitted by two high-frequency carriers, carrier f 1 transmission 1, carrier f2 transmission 0, or carrier f 1 transmission 0, carrier f2 transmission 1.

Other communication systems:

ASK amplitude-frequency keying communication system uses high-frequency carrier to transmit digital signals. There is carrier output when transmitting 1, and no output when transmitting 0.

PSK absolute phase shift keying communication system uses high frequency carrier to transmit digital signals. When transmitting 1, the carrier is output in phase, and when transmitting 0, the carrier is output in phase. Or transmit the in-phase output carrier at 0 and transmit the in-phase output carrier at 1.

Compared with phase shift keying communication system, DPSK uses high frequency carrier to transmit digital signals. When the initial phase of the signal in the next codeword period is in phase with the last phase of the previous codeword period, it means that the transmission is 0, and when it is inverted, it means that the transmission is 1.

As for the thesis, you can refer to the books on the principle of communication system as the theoretical basis, and the topic of the thesis can be designed and analyzed by using system view communication system analysis software.