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东京芝浦电气综合研究所提出了可以在垂直磁记录介质上记录、再生模拟信号的PWM(Pulse Width modulation)方式。PWM方式已经用于面内记录的数据记录器,缺点是可以记录的信号频带非常窄。新近提出的PWM方式利用了垂直磁记录方式的特征,即,①直至短波长还没有相位推移,可以进行矩形波记录;②可以记录的最短波长比可以再生的最短波长短得多。选择的载波频率fc是信号上限
Tokyo Shibaura Electric General Research Institute proposes a PWM (Pulse Width Modulation) method that can record and reproduce analog signals on a perpendicular magnetic recording medium. The PWM method has been used for in-plane recording data recorders. The disadvantage is that the signal band that can be recorded is very narrow. The newly proposed PWM method takes advantage of the features of the perpendicular magnetic recording method, that is, ① rectangular wave recording can be performed until the short wavelength has not passed yet; ② the shortest wavelength that can be recorded is much shorter than the shortest wavelength that can be reproduced. The selected carrier frequency fc is the upper limit of the signal