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Dasd-Based Signal Correlators

IP.com Disclosure Number: IPCOM000043988D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Johnson, M: AUTHOR

Abstract

Direct-access storage device (DASD)-based signal correlators have a magnetic disk system in which the normal concentric tracks are replaced by one or more continuous spirals, and the disk area is used as, at least, one delay line. Data may be fed into the delay line via a moving write head 11 which follows the spirals 13 using an optical or capacitive servo. One or more read heads 12 serve to extract the data after a time delay given by the radial separation of read 12 and write 11 heads, and the track density/disk velocity combination. The maximum time delay is given by the time taken to write the whole disk surface. Any such delay line may be characterized by a figure of merit called the time bandwidth (TBW) product. This is equivalent to the total number of bits stored in the line.

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Dasd-Based Signal Correlators

Direct-access storage device (DASD)-based signal correlators have a magnetic disk system in which the normal concentric tracks are replaced by one or more continuous spirals, and the disk area is used as, at least, one delay line. Data may be fed into the delay line via a moving write head 11 which follows the spirals 13 using an optical or capacitive servo. One or more read heads 12 serve to extract the data after a time delay given by the radial separation of read 12 and write 11 heads, and the track density/disk velocity combination. The maximum time delay is given by the time taken to write the whole disk surface. Any such delay line may be characterized by a figure of merit called the time bandwidth (TBW) product. This is equivalent to the total number of bits stored in the line. The best devices currently used in this application are surface acoustic wave plates. At 1 GHz bandwidth, 10 cm length, wave velocity 5000 m/s, the TBW is 2.10**4. An optical fiber may also be used as such a delay line. At 1 GHz bandwidth, 10 km length, TBW = 5.10**4. A conventional 14" magnetic disk configured as described above has TBW 2.10**8, far greater than the other examples. However, its data rate is rather limited. This disadvantage may be overcome through extension to higher rotational velocities.

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