外文翻譯--通信系統(tǒng)簡介-其他專業(yè)-展示頁
2025-01-31 00:36本頁面
【正文】 ustrates this very simple idea. The information from the source will generally not be in a form that can travel through the channel, so a device called a transmitter will be employed at one end and a receiver at the other. Figure 1 simple munication system The source or information signal can be analog or digital. Common examples are analog audio, video signals and digital data. Sources are often described in terms of the frequency range that they occupy. Telephonequality analog voice signals, for instance, contain frequencies from 300Hz to 3kHz, while analog highfidelity music needs a frequency range of approximately 20Hz to 20kHz. Digital sources can be derived from audio or video signals can have almost any bandwidth depending on the number of bits transmitted per second, and the method used to convert binary ones and zeros into electrical signals. A munication channel can be almost anything: a pair of conductors, an optical fiber or a free space that we live. Sometimes a channel can carry the information signal directly. For example, an audio signal can be carried directly by a twistedpair telephone cable. On the other hand, a radio link through free space cannot be used directly for voice signals. Such situation require the use of a carrier wave will be altered, or modulated m, by the information signals in such a way that the information can be recovered at the destination. When a carrier is used, the information signal is also known as the modulating signals. Technology is at the core of many new and emerging digital information products and applications that support the information society. Such products and applications often require the collection, sometimes in real time. The ability of technology to handle real world signals digitally has made it possible to create affordable, innovative。 and high quality products and applications for large consumer market for example: digital cellular
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