文件名称：Versatile Digital QAM Modulator
文件大小：586KB
文件格式：PDF
更新时间：2012-12-21 12:47:43
QAM
Introduction With the advancement of digital entertainment and broadband technology, there are various ways to send digital information to end users such as cable and satellite subscribers. The current digital cable systems deployed around the world use the Quadrature Amplitude Modulation (QAM) standard, which defines the input data framing structure, channel forward error encoding, filtering, and QAM mapping. With digital TV, the typical downstream signal uses either a 64- or 256-QAM scheme. The data source is either ATM packets or MPEG2 transport packets (used for digital TV applications). The differences in the QAM standards are in the error coding section, which is broken down ? by Annex A, B, or C. The North American standard uses Annex B for encoding. The Stratix II FPGA logic structure combined with enhanced DSP blocks offers a flexible way to implement the key elements of the QAM signal processing path in any region. Table 1 lists the different digital cable standards deployed in key areas of the world.