用於混合同軸光纖系統的差動編碼四元相位移鍵射頻調變解調器之設計與製作

Abstract

本論文設計了可使用於混合同軸光纖(HFC)系統的每秒兩百零四萬八千位 元差動編碼四元 相位移鍵(DE-QPSK)射頻調變解調器.藉由我們設計的頻 率合成器,它可在任何有線電視頻 段傳收DE-QPSK信號.基頻信號處理包括 了攪碼/解攪碼器,自正交捲積碼器和多數決邏輯 解碼器,還有差動編碼 與解碼器-而這些都整合在一顆Xilinx FPGA 4003A中.整個HFC系統 都被 實際製作,且DE-QPSK信號藉由使用Nd-YAG雷射和外調式調變器而得以在光 纖上傳送. 整個系統的效能是藉由測量系統的位元錯誤率(BER)對載波雜 訊比(C/N),結果和理論值 做比較有5dB的功率耗度. In this thesis, we design a 2.048Mbps RF Differential-encoded Quadrature -Phase-Shifted-Keying (DE-QPSK) modem that can be used in HFC communication systems. By using frequency synthesizers designed by ourselves, we can transmit and receive DE-QPSK signal in arbitrary CATV band.Baseband digitalsignal processing including a scrambler/ descrambler,a Self-Orthogonal convolutional encoder and majority logic decoder, a differential coder / decoder - all of which are integrated in Xilinx FPGA 4003A's. The overall HFC system are implemented and the QPSK signals transmitted through fiber by using a Nd-YAG laser and an external modulator.The Bit-Error- Ratio (BER) performance of this system is measured against Carrier-to-Noise-Ratio (C/N) and a 5dB power penalty at 10^-7 was measured when compared with theoretical results.