目前主流的光記錄系統技術為DVD，其擁有外型輕薄之優點，利於攜帶，隨著目前對於多媒體處理技術進步以及對視聽的高品質需求，已經取代傳統的軟碟、錄音帶等媒體，而大幅地提昇了記錄系統儲存容量。而光記錄系統如CD、DVD，存在有聚焦( Focus )及軌道伺服( Track )信號位於低頻部份，所以為了在讀取此信號時不會受到來自消息低頻成份的干擾，所以必須要降低消息在低頻頻率下成份的內容，達到無直流成分的要求。本論文主要就是在這方面的探討。 本論文主要分為二部份，第一部分先介紹結合部分反應信號與最佳估算偵測（Partial-Response Maximum Likelihood , PRML）的特性而發展出的TMTR碼，在解決了碼字連結問題後，使用部分替代碼字的方法，限制跳躍數位總和在一有界範圍內，以達到無直流成分的要求。並探討在不同k值時，替代碼字的數量也不同，在功率頻譜密度的分析與比較。 第二部分先介紹B. Vasic和K. Pedagani提出的方法，使用低密度同位元檢查碼，省略(d,k)跳躍長度限制碼( Run-Length-Limited , RLL , Codes )的編碼及解碼，而能滿足(0,k)限制以符合資料在媒體上儲存的條件，並利用S. Babvey和S. W. McLaughlin提出的解碼器，再加以改進應用在光學記錄上，以能達到無直流成分的要求。 Nowadays the popular technology of optical recording system is “DVD”, which is light and slim in shape as its advantage and is convenient for carrying. As and the demands for high-quality audio and video, the conventional soft disk and tape had been replaced and raised the storage capacity of recording system. The optical recording system such as CD、DVD, which consist in Focus and Track signal located in the part of low frequency, while in order to read this signal and that wasn’t interfered from the low frequency part of information, so you must lower the content of information in low frequency and achieve the demand for DC-free. The paper is discussed in this way. The paper is organized as two sections. In Section 1, the combination of partial response signal and Maximum Likelihood Detection (PRML) is introduced first and develop the TMTR code. After solving the problem of codeword combination, the method of replaced codeword partially is used and the running digital sum within the limited range to achieve the demand for DC-free. When in variety of k value the number of the replaced codewords are also different. We analyzed and compared the difference conditions in PSD. In Section 2, the method proposed by B. Vasic and K. Pedagani is introduced first. The idea is to completely eliminate a constrained code and, instead, impose the constraint by the deliberate introduction of bit errors before transmission. Finally the decoder proposed by S. Babvey and S. W. McLaughlin is used and improved further and applied in optical recording system, so the demand for DC-free is achieved.
