PRML技術在高密度磁光碟機上之應用

Abstract

針對磁光碟機系統，我們提出一簡單、可行的訊號處理技術，以提高資料 的存取密度。 在部份反應最大可能性 (PRML) 們設計了一簡單的等化器 ，這等化器由一固定的等化器及一適應性等化器之串接組成。前者主要目 的為補償碟片平均中軌處的通道脈衝響應和部份反應訊號架構之間的差異 。後者則是為了補償通道因不同軌道位置而產生的變動。 在最大可能性 之檢測器部分， Viterbi演算法， 可快速、精確地檢測出資料。 有客觀 的磁光碟存取系統特性為依據，我們利用了3.5英吋，波長 780毫米的 O- PAS 3000q道的特性。我們一共用了四種不同的方法 A測量的結果顯示磁 光碟機的通道特性比較接近第一類或第二類的 H測量的結果為模型，我們 模擬了我們所設計的PRML系統之特性。模擬結果顯示， 我們提出的系統 可提高比現有系統約百分之七十的資料存取密度。 An equalization technique that is based on partial response maximum likelihood detection (PRML) has been used in high- density drives and is very likely to be applied to other mass storage optical disk drive and the tape drive. The purpose of this study investigate the feasibility and related system design issues in the PRML technique to MO disk drive. We choose an existing optical testing equipment, namely, the the testing plan. The purpose is to understand the (read) channel characteristic by measuring the channel impulse response of an disk drive (in this case, an MO drive). Four characterization methods are used and the measurement results are tested. All approaches indicate the MO channel is a close approximation of either a Class I or partial response channel. From the measurement results we find correlation approach which utilizes the autocorrelation property of PN sequences yield the most accurate result. Using the measured channel response, an optical response (PR) implemented by using a fixed-weight FIR filter followed by a PR adaptive equalizer. The former is to PR- equalizing the mean while the latter is responsible for the compensation of theon resulted from different radial positions. The combined impulse the recording channel and the PR equalizer becomes that of a PR then use a very efficient maximum likelihood sequence detector demodulate the read data. Our simulation results indicate that PRML system when compared with a current available MO system (3.5 wavelength 780 nm), can yield as much 70\% more linear density.