With the addition of DPSK baseband signal, the anti-dispersion capability of uplink signal and baseband signal is enhanced, the downlink transmission performance and receiver sensitivity become better. Besides, the influence of modulator at the central station on the receiver sensitivity is reduced. 增加传输DPSK基带信号后,上行链路信号和DPSK基带信号的抗色散能力强,下行链路的传输性能和接收端的灵敏度变好,还使中心站调制器对系统接收端灵敏度的影响减少。