Bit Jitter

To put more data on a disk, you must decrease bit spacing.  Good media can record closely-spaced bits accurately, with adequate signal strength and without excessive intersymbol interference.  Bit position and amplitude Jitter are fundamental sources of analog noise and digital errors.  Now you can analyze Magnetic Force Microscope (MFM) images to obtain jitter measurements without interference from cross-talk and other read head limitations.

MFM image of a constant frequency test pattern on a hard
disk.  The Magnetic Force Microscope senses the magnetic
field just above the disk surface.  15 micron scan.

Bit position and amplitude measurements from 1 MFM image.  In a constant frequency test pattern, the bits ideally have equal amplitude and spacing.  Variation is a measure of media noise and other micromagnetic characteristics.  Amplitude and position variation increase with frequency (bit density). These results are tools used by disk engineers to set the maximum bit density.

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updated 04/09/2007

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