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发表于 2009-1-16 11:17:35
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ADSL receiver design guide
Introduction
Consumer desire for faster Internet access is driving the demand for very high data rate modems. A digital subscriber line (DSL) implementation speeds data to and from remote servers with data rates of 512Kb/s to 8Mb/s, much faster than current 56Kb/s modem alternatives. This speed of data communication is providing the Internet with the capability to transfer information in new formats such as full-motion video, while greatly improving the timeliness of conventional information access.
One very important feature of DSL technology is that the connection is handled through a normal telephone line; therefore, no special high speed cables or fiber optic links are required and every home and office is most likely DSL ready. Another feature is that the data interface can operate simultaneously with normal voice communication over the same telephone line. This allows the modem to be connected at all times and not interfere with the use of the same line for normal incoming and outgoing phone calls or faxes.
The real "magic" of DSL technology stems from the application of digital signal processing (DSP) algorithms and data coding schemes. The implementations have built-in intelligence to accommodate the wide variations of data transmission signal conditions encountered with each connection through the telephone switching network. Sophisticated ASICs have been developed to provide small modems for PCs and handheld devices and the ability to compact many DSL lines on a single PCB card for telephone central-office deployment.
However, as is the case with almost any system, DSL still requires fundamental operational amplifier functions to put the signal on to the phone line and to pick off the small signals received at the other end. Although many system designers are competent and comfortable with DSP and all things digital, they often find their understanding of analog issues to be a bit rusty when it comes to implementing the physical connection to and from the telephone line. This series of articles will provide an overview of the requirements placed on the amplifiers and provide guidelines to component selection and the implications on distortion performance and power consumption and dissipation, the most important system issues related to the analog components.
【文件名】:09116@52RD_ADSL Line Driver-Receiver Design Guide.doc
【格 式】:doc
【大 小】:520K
【简 介】:
【目 录】:
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