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传输信息有两种方式:基带传输和调制传输。由信源直接生成的信号,无论是模拟信号还是数字信号,都是基带信号,其频率比较低。基带传输就是将信源生成的基带信号直接传送,如:音频市话、计算机间的数据传输等。基带传输系统的结构较为简单,但难以长距离传输,因为一般的传输信道在低频处的损耗都是很大的。为进行长途传输,必须采用调制传输的方式。调制就是将基带信号搬移到信道损耗较小的指定的高频处进行传输,调制后的基带信号称为通带信号,其频率比较高。DVB传输系统是数字传输系统,因此其中采用的调制技术是数字调制技术。
There are two ways to transmit information: baseband transmission and modulation transmission. The signal generated directly from the source, whether it is an analog signal or a digital signal, is a baseband signal with a low frequency. Baseband transmission is the direct generation of the baseband signal generated by the source, such as: audio local calls, computer data transfer. The structure of the baseband transmission system is relatively simple, but it is difficult to transmit over long distances because the loss of a common transmission channel at a low frequency is large. For long-distance transmission, modulation transmission must be used. Modulation is to move the baseband signal to the designated low frequency channel loss at the designated high-frequency transmission, the modulated baseband signal is called the passband signal, the frequency is relatively high. DVB transmission system is a digital transmission system, so the modulation technology used is digital modulation technology.