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Burst mode readout of RF-MAMMOS for reduced power consumption Disclosure Number: IPCOM000009928D
Publication Date: 2002-Sep-30
Document File: 2 page(s) / 61K

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Burst mode readout of RF-MAMMOS for reduced power consumption..

1. Background

In the last few years, a number of magneto-optical domain expansion (DomEx) techniques have been proposed to increase the readout resolution, and thus the storage capacity, far beyond what can be reached using the optical diffraction limit. The most promising are RF-MAMMOS (Magnetic Amplifying Magneto-Optical System), ZF- (Zero Field) MAMMOS and DWDD (Domain Wall Displacement Detection). The main advantages of RF MAMMOS are: - simple substrate compared to the other two techniques, which require ultra smooth surfaces and groove side walls; - large signal, also for smallest marks (about two times larger than for ZF-MAMMOS and DWDD); - simple signal processing (only threshold detection, no PRML, Viterbi, etc.); and - (most likely) highest density and highest data rate. For portable applications, where power consumption has to be kept to a minimum, a disadvantage of RF-MAMMOS is that a modulating external field has to be applied during readout, in contrast to the other techniques. Recently, several field switching strategies and waveforms have been proposed to improve the readout performance an to reduce power consumption.

In many portable (magneto-) optical storage systems a kind of burst mode approach is used to enable continuous playback despite possible vibrations or shocks. A buffer memory is kept filled by intermittent readout at a higher data rate than the average output data rate from the buffer memory to the user. By switching off, for example, the spindle motor during the periods when reading is paused, a reduction in power consumption can be achieved. In Sony's MiniDisk system, a power save mode is provided for reducing the power consumption during recording with magnetic field modulation (MFM). The disk speed, and thus the (maximum) data rate, are doubled in this mode. Actual recording is done in only h...