85-2 Digital Data, Analog Signals 编码技术(数字调制技术) .ii: The most familiar use of this transformation is for transmitting digital data through the public telephone network. The telephone network was designed to receive, switch, and transmit analog signals in the voice -frequency range of about 300 to 3400HZ. It is not at present suitable for handling digital signals from the subscriber location. Thus digital devices are attached to the network via a modem, witch converts digital data to analog signals, and vise versa JiE: The modulation involves operation on one or more of the three characteristics of a carrier signal: amplitude, frequency, and phase. Accordingly, there are three basic encoding or modulation techniques for transforming digital data into analog signals. as illustrated in Figure 5.7(E6) Amplitude-shit keying(ASK) FI cy-shift keying(FSK) Phase-shift keying(PSK)
16 §5-2 Digital Data, Analog Signals 1. 编码技术（数字调制技术） 用途：The most familiar use of this transformation is for transmitting digital data through the public telephone network. The telephone network was designed to receive, switch, and transmit analog signals in the voice –frequency range of about 300 to 3400Hz. It is not at present suitable for handling digital signals from the subscriber location. Thus digital devices are attached to the network via a modem, witch converts digital data to analog signals, and vise versa. 方法：The modulation involves operation on one or more of the three characteristics of a carrier signal: amplitude, frequency, and phase. Accordingly, there are three basic encoding or modulation techniques for transforming digital data into analog signals, as illustrated in Figure 5.7（E6） ◼ Amplitude-shit keying (ASK) ◼ Frequency-shift keying (FSK) ◼ Phase-shift keying (PSK)
00110100010 (a) Amplitude-shift keying 0 00010 0000 b) Frequency-shint keying 00 0010 (e)Phase-shift keying Figure 5.7 Modulation of Analog Signals for Digital Data 17
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