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说明：  设计一个理想通信系统，实现信息字符流的传输。 发射器： 将消息（字符串形式）编码成一个符号序列； 用脉冲成形将串符号序列转变成模拟脉冲信号； 将模拟脉冲信号调制到载波信号上。 接收器： 对接收的信号进行采样； 解调信号成基带信号； 将信号恢复成字符串。(Design an ideal communication system, the realization information transmission of character flow. Emitters: < 1 > will news (string form) coding into a symbol sequence < 2 > by using a pulse forming will string of symbols into a simulation pulse signal sequences < 3 > will simulate the pulse signal modulation to carrier signal. Receiver: < 1 > of received signal sampling < 2 > demodulation signal into baseband signal < 3 > will signal back into a string.)