Noise characterization by voronoi cell modeling for perpendicular double layer media
Noise characterization by voronoi cell modeling for perpendicular double layer media
复制标题
通过垂直双层介质的 voronoi 单元建模进行噪声表征
DOI：
10.1109/intmag.2000.871880
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Y. Nakamura
中科院分区：
文献类型：
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作者：
K. Miura;H. Muraoka;Y. Sugita;Y. Nakamura
~~对磁盘上指定位置的差分读回波形进行平均，以使用基于互相关的精确相位匹配来降低电子噪声。然后，将包含40个孤立脉冲的平均波形切出并累积，使得所有孤立脉冲与固定转变点对准。计算累积波形的标准偏差（归一化为脉冲幅度）。图1中描绘了时域测量的结果。在跃迁点处观察到一个明显的噪声峰，表明跃迁噪声占主导地位，而不是均匀加性噪声。如图2所示，还阐明了读回脉冲的上升沿和下降沿之间的正相关性，这表明过渡噪声不是由脉冲宽度或脉冲幅度的变化引起的，而是由位置抖动引起的。使用磁力显微镜（MFM）对磁性转变进行直接检查，显示出磁性转变的微观交叉轨迹波动。波动的过渡线对应于穿过磁性“团簇”的边界，其尺寸约为80 nm [2]。这一事实表明，噪音来源于磁“集群”。基于Voronoi胞元模型的噪声估计假设介质中多个相邻的晶粒是磁性连接在一起的，并且是一致切换的，我们建立了基于Voronoi胞元的噪声模型，每个胞元代表一个被称为“簇”的连接增益。我们计算过渡抖动和均方根（RMS）噪声电压：生成的组装Voronoi细胞被切成微轨道和洛伦兹脉冲响应每个微轨道叠加。图3中示出了时间轴上的模拟过渡噪声的计算的标准偏差。计算结果与实验结果吻合较好
~~~~~~~~~~~~~~~~ disk was the same ah for our previous error rate measurements [I]. Differentiated readback waveforms for a designated position on the disk were averaged to reduce electronics noise using precise phase matching based on cross-correlation. Then, the averaged waveform containing 40 isolated pulses was cut out and accumulated so that all the isolated pulses were aligned with a fixed transition point. The standard deviation, normalized to the pulse amplitude, was calculated for the cumulative waveform. A result of the time domain measurement is depicted in fig. 1. A clear noise peak at the transition point was observed, which indicated that transition noise was dominant rather than uniformly additive noise. A positive correlation between the rise-edge and the falliug-edge of the readback pulses was also clarified, as shown in fig. 2, which showed that the transition noise wasn’t caused by a variation of pulse width or pulse amplitude, but position jitter. Direct examination of the magnetic transitions using a MFM, Magnetic Force Microscope, showed microscopic cross-track fluctuations of the magnetic transition. The fluctuated transition lines corresponded to boundaries running through magnetic ‘clusters’ whose sizes were around 80 nm [2]. This fact suggested that the noisc originated from the magnetic ‘clusters’. Noise Estimation usins Voronoi Cell Modeling Assuming that several neighboring crystallographic grains of the medium were magnetically connected together and switched in unison, we established il noise model using Voronoi cells; each cell represented the connected gains which are referred to as a ‘cluster’. We calculated transition jitter and root-mean-squared (RMS) noise voltage: a generated assembly of Voronoi cells was sliced into microtracks and the Lorentzian pulse responses for each microtracks were superposed. The calculated standard deviation of the simulated transition noise on time axis is shown in fig. 3. The results were in good quantitative agreement with the experimental result