June 22, 2004
Professor of Mechanical Engineering and ECE Bill Messner was issued a patent for his research project, "Frequency Modulation Pattern for Disk Drive Assemblies." Co-inventors Jimmy Zhu, ABB Professor of ECE; Professor of MSE and Physics, and their former student Xiandong Lin, who is now at Seagate, conducted the work through the Data Storage Systems Center.
The patent is for a new servo pattern for magnetic hard disk drives. According to Messner, the servo pattern of a disk drive is a special arrangement of magnetic domains separated from the data. When the head of the disk drive passes over the servo pattern, the channel demodulates the readback signal to determine the radial position of the head relative to the disc.
"Our pattern is new in that the position information is encoded in the frequency of the readback signal," Messner explained. "The frequency of the readback signal varies linearly with the radial position. This new pattern may be very useful for discs formatted outside of the disk drive, so-called 'preformatted media.'"
The top portion of the figure above shows one embodiment of the new pattern. The bottom portion shows two representative readback waveforms. The top waveform has a lower frequency than the bottom waveform, because the same number of cycles are spread over a longer time.