用于HD-DVD的PRML检测系统的设计与实现

对用于高密度DVD(HD-DVD)光盘存储系统的部分响应最大似然(PRML)检测器的设计和实现进行了详细研究.通过比较光盘信道的线性模型与记忆长度为4—7的部分响应(PR)多项式的幅频特性，从提高PR均衡器和维特比检测器性能的角度，对目标PR的记忆长度及系数的选择进行了详细分析.仿真计算的信噪比-误码率曲线说明，当目标PR的记忆长度为7且与光盘信道模型的幅频特性接近时，PRML检测器的性能最优.还详细描述了PRML系统中维特比检测器的硬件结构，分析证明当目标PR的记忆长度增加时，维特比检测器的逻辑单元规模     

用于多阶光盘游长检测的PRML系统

对用于多阶光盘游长检测的部分响应最大似然（PRML）检测器的设计和实现进行了详细研究。分析了多阶光盘的编码形式,并将编码进行简化以减小维特比检测器的路径数和运算复杂度。为了提高PR均衡器和维特比检测器的性能,分析了目标PR多项式系数和记忆长度的选择。阐述了多阶光盘游长识别的维特比算法,对算法进行仿真,分析了维特比算法的识别效果,并与与传统识别算法的效果进行了比较。     

湍流信道下差分索引移位键控直流偏置光OFDM

针对现有光无线正交频分复用（OFDM）索引调制均需接收端已知信道状态信息的问题，通过构建满足差分运算的时频弥散矩阵进行索引映射，提出了一种差分索引移位键控光OFDM方案。推导出了该方案在最大似然准则下的平均误码率上界，并与子载波索引移位键控直流偏置光OFDM(SISK-DCO-OFDM)系统进行了性能对比。其次，依据差分信号的特点，构造了一种适用于机器学习的差分信号特征向量，并结合径向基神经网络提出了一种多分类检测器，有效降低了译码复杂度。结果表明，所提差分索引方案有效避免了复杂的信道估计，同时在高信噪比下获得了近似SISKDCO-OFDM的误码性能。所提检测器取得了近似差分最大似然检测算法的误码性能，而且复杂度大大降低，例如当子载波块长度为2和4时，所提检测器的复杂度分别降低了16.67%和70%。     

基于最大似然准则的多波长OCDMA接收机的最佳判决门限研究

采用最大似然准则,研究了多波长光码分多址接收机的最佳判决门限值.通过检测信道的光信号能量,接收端估计出信道的并发用户数,并通过最大似然准则得到了最佳判决门限值与并发用户数、码字参量的变化关系.当并发用户数超过一定值后,最佳判决门限值将随并发用户数量变化,相应地改变接收机的判决门限值.根据最佳判决门限值,得到了多波长光码分多址系统误码率与并发用户数的关系.理论分析和模拟结果表明,采用最大似然准则得到的最佳判决门限值,MW OCDMA系统的误码率将明显降低.     

一种深空背景空间小目标条痕检测算法

针对深空慢速运动目标(目标在焦面的运动速度小于1 pixel/frame)提出了一种最大似然条痕检测算法,能够在较低信噪比情况下实现有效的慢速目标检测。算法将目标脉冲形状信息引入信号模型中,是最大值投影算法的改进形式。建立基于高斯噪声分布的图像信号模型,在此基础上推导了最大似然条痕检测算法模型;分析该算法的实时性及其理论探测性能;采用蒙特卡罗仿真方法比较最大似然条痕检测算法与最大值投影检测算法的检测性能。仿真结果表明,输入信噪比为3.5时,最大似然条痕检测算法的探测概率为95%,其相同探测概率条件下所需信噪比比最大值投影算法降低了2.5(即最大值投影算法要达到95%的检测概率,所需信噪比为6)。算法实时性分析表明,最大似然条痕检测算法的实时处理能力为31.25 Mb/s。     

波形调制多阶光盘的自适应阶次检测

波形调制多阶的时钟恢复后的读出信号跟符号序列没有对应关系,部分响应最大似然(PRML)检测不能直接使用。提出了一种基于最小欧氏距离的自适应阶次检测方法,该方法用实际波形与标准波形的欧氏距离作为阶次检测的依据。自适应调整能让设定的标准波形值向实际波形接近。保护机制能防止设定的标准波形严重偏离真实值。实验结果表明,在不调整参数的情况下,该检测方法能对不同批次盘片获得相当的阶次错误率——2×10~(-4)以下。该方法对缺陷盘片也有很好的适应性。使用该检测方法的播放系统实现了高清视频的连续稳定播放。     

利用目标信道特性约束的信道匹配检测算法

浅海有源声呐的探测性能主要受到多途扩展以及混响干扰的影响。为了提高声呐系统的检测性能,根据双扩展信道匹配原理,结合混响信道与声呐目标信道特点,提出了一种基于回波特性约束的信道匹配检测算法。该算法通过最小二乘匹配追踪算法估计信道稀疏响应,并根据混响和目标信道的扩展差异,通过约束目标信道扩展对稀疏信道响应去冗余,得到更精确的目标回波信道响应。利用该信道响应进行信道匹配检测,可以进一步提高信混比处理增益。数值仿真结果表明所提算法可以有效汇集多途信号能量并抑制混响干扰,提高声呐系统的检测性能;海试数据处理结果显示,在试验信道条件下,所提算法处理结果的峰值信混比,与匹配滤波相比提升约7~12 dB,与传统自适应相关器相比提升约6~7 dB。      

一种基于单似然检验的高光谱图像小目标检测器

针对背景和目标的先验光谱特征未知的条件,给出一种基于单似然检验的高光谱图像小目标检测器。小目标相对于背景的低概率性使得高光谱图像数据对目标光谱信号的矩特征几乎不施加约束,可在最大熵条件下将广义似然比检验简化为对背景似然的单似然检验;利用全部数据样本建立无参估计模型以充分利用样本信息,从而得到基于单似然检验的高光谱图像小目标检测器。该检测器避免了统计模型误差和不明确物理含义特征对实际高光谱图像数据检测带来的影响。使用可见光/近红外波段机载I型实用型模块化成像光谱仪(OMIS-I)高光谱图像进行了实验,实验结果及相应理论分析表明该算法可有效检测高光谱图像中的空间低概率目标。     

光盘道间距及其信道轨迹长度的测量

基于光盘的结构,将光盘抽象为一个反射光栅的模型,从而测出了光盘的道间距及信道轨迹长度.     

基于多检测器最大熵融合的多通道光谱图像异常检测

提出了一种多检测器最大熵融合的多通道光谱图像异常检测算法.选择多个不同的异常检测器,并利用自适应窗宽非参核密度估计方法估计其各自的输出分布,保留了多通道光谱图像数据的“长尾”特性,且避免了先验模型假设带来的模型误差.将各原始检测器的输出投影到具有标准正态边缘分布的变换空间中,利用变换空间中模型化的最大熵融合规则实现多检测器的决策级最优概率融合.在原数据空间通过似然函数的检验完成多通道光谱图像的目标检测.利用机载EPS-A航拍多通道光谱图像进行了实验,实验结果表明了算法的有效性.     

Data page reconstruction method based on two-dimensional soft output Viterbi algorithm with self reference for holographic data storage

This study introduces a two-dimensional (2D) partial response maximum likelihood (PRML) method to reconstruct a degraded data page having 2D inter-symbol interference for holographic data storage. The proposed 2D PRML method consists of 2D partial response (PR) target, 2D equalizer using least mean square algorithm, and 2D soft output Viterbi algorithm (SOVA) having just two one-dimensional (1D) SOVAs in horizontal and vertical directions. To accurately organize a trellis diagram of the 1D SOVA in structural accordance with the 2D PR target, this study proposes the self-reference process for the extrinsic information in the 1D SOVA. Finally, simulation results show that the proposed method has bit error rate performance similar to that of modified 2D SOVA having four 1D SOVAs despite the relatively low computational complexity. Moreover, parallel processing is possible in the two 1D SOVAs through the self-reference process.     

Improved partial response maximum likelihood method combining modulation code for signal waveform modulation multi-level disc

In this paper, we describe an improved adaptive partial response maximum likelihood （PRML） method combining modulation code tbr signal waveform modulation multi-level disc. This improved adaptive PRML method employs partial response equalizer and adaptive viterbi detector combining modulation code. Compared with the traditional adaptive PRML detector, the improved PRML detector additionally employs illogical sequence detector and corrector. Illogical sequence detector and corrector can aw）id the appearance of illogical sequences effectively, which do not follow the law of modulation code for signal waveform modulation multi-level disc, and obtain the correct sequences. We implement the improved PRML detector using a DSP and an FPGA chip. The experimental results show good performance. The higher efficient and lower complexity can be obtained by using the improved PRML method than by using the previous PRML method. Meanwhile, resource utilization of the improved PRML detector is not changed, but the bit error rate （BER） is reduced by more than 20%.     

Performance of GPRML-AR system in perpendicular magnetic recording channel with thermal decay

The bit-error rate (BER) performance of the generalized partial response maximum likelihood with autoregressive (GPRML-AR) channel model system in perpendicular magnetic recording (PMR) channel with thermal decay is obtained. The 128/130(0,16/8) run-length-limited (RLL) code is used as a recording code. The GPR channel consists of the PR1 channel followed by the reduction circuit of predicted noise. The BER performance is evaluated by computer simulation using a thermal decay model. The model has been obtained by using an approximate equation that represents amplitude degradation of the reproducing waveform with elapsed time based on the experimental data for CoPtCr-SiO₂ PMR media. The Viterbi detector with an AR channel model is employed. Furthermore, long-term degradation of the required SNR to achieve a BER of 10⁻⁴ with elapsed time is obtained and the performance is compared with that of PR1ML system. The results show that the poorer the thermal stability of the medium becomes, the larger the SNR gain of the GPR1ML-AR system over the PR1ML system becomes. The SNR gain also increases with elapsed time.     

蓝光高密度光盘驱动器中聚焦误差特性分析

高密度数字视盘(HD-DVD)是一种新型蓝光存储技术，可以满足数字高清视频节目的播放要求.介绍了用于HD-DVD驱动器中的刀口法调焦方案，基于菲涅耳公式和标量衍射理论，推导了刀口法调焦的HD-DVD驱动器中聚焦误差信号与离焦量之间关系的计算模型.应用该计算模型，分析了不同离焦量时探测器上光强分布情况.计算得到的聚焦误差信号与离焦量之间的关系曲线与实验测得的“S型”曲线相一致，证明了计算模型的正确性.进一步分析了正焦点时由于记录符调制而引起的聚焦误差的干扰信号，计算结果表明这种干扰的强度小于4.5%.分析表 关键词： 光存储 刀口法 聚焦误差 标量衍射     

Analytical characterization of detection SNR for PR target design in Viterbi-based receivers

In this paper, we address the problem of designing the optimum partial-response (PR) target that results in the best bit-error-rate (BER) performance in Viterbi-like detectors when applied for signal detection in digital magnetic recording systems. We present a detailed analysis of the effective detection signal-to-noise ratio (SNR_eff), which is closely related to the BER performance of a Viterbi detector. We show that SNR_eff is a concave function with a unique global maximum corresponding to the magnitude frequency response of the optimum targets. Thus, any simple search approach is guaranteed to reach the optimum target. We consider the cases of single dominant error event and multiple dominant error events. Numerical and simulation results are presented to corroborate our analytical results for perpendicular magnetic recording channels.     

Dependence of error patterns and BER performance on write pre-compensation in GPRML channels

Nonlinear transition shift (NLTS) influences the performance of PRML channels in perpendicular magnetic recording. For NLTS, it is thought that write pre-compensation is useful to write the transition at the intended position. In this paper, we study the influence of NLTS on the BER performance of GPRML channels and show the appropriate amount of pre-compensation for GPRML channels both with and without a post-processor (PP) to achieve better BER performance. The results show that the widening the shortest bit length by NLTS brings the BER improvement to GPRML channel and the write pre-compensation is useful for a GPRML channel with PP.     

Performance of run-length limited (4, 18) code for optical storage systems

In this paper, the authors investigate the performance of recently presented run-length limited (4, 18) code for high density optical storage systems. The construction of the code is described simply. The code has code rate R = 1/3 and density ratio (DR) = 1.67. The bit error rate (BER) performance for decision feedback equalizer (DFE) and partial response maximum likelihood (PRML) detector are simulated, considering signal-to-noise ratio (SNR) and optical channel jitter. The result shows that the performance of the code is acceptable. The encoder and decoder of the code are implemented by complex programmable logic device (CPLD) chip and the hardware resources required for encoder and decoder arelow.     

Recording characteristics of high-density thin optical disk using near-field optical recording

We report on the recording characteristics of a near-field optical recording thin optical disk (NFR-TOD). We proposed a new cooling-less-type write strategy for recording, applied it to the NFR-TOD experimental system, and also applied a partial response maximum likelihood (PRML) signal processing, which was evaluated and optimized the PR coefficient for playback signals of the prototype NFR-TOD. The NFR-TOD has a track pitch of 160 nm and improved recording characteristics. The experimental results of the prototype NFR-TOD and the system indicate sufficiently low bit error rates (bERs) for recorded data at a fourfold higher recording density than the current Blu-ray disk.     

新一代高密度数字多用光盘(HD-DVD)研究进展

文章综述了新一代高密度数字多用光盘的研究进展，介绍了多种新型蓝绿光高密度可录和可擦重写光盘存储材料，讨论了高密度数字多用光盘所面临的问题以及其解决方法，最后提出了中国超高密度光盘存储技术发展的研究思路。