Method and Apparatus for Improving Signal-to-Noise Ratio for Hard Disk Drives

Abstract

A hard disk drive comprising a plurality of read/write heads oriented to serially read data from the magnetic media of the disk drive. The head output signals are delayed and combined to provide a time aligned composite signal for determining the value of the data bits read from the disk drive. An improved signal-to-noise ratio is provided according to the teachings of the present invention by combining the signal components from the plurality of heads, as the signal components are added algebraically while the noise components are combined as root mean square values. Thus the overall signal-to-noise ratio is improved, resulting in a greater probability of correctly determining the stored data.

1 . An apparatus for storing information in the form of data bits, comprising: 
 a data storage medium comprising storage regions, wherein a data bit is represented by a state of one or more storage regions;    a plurality of read heads in proximate relation to the data storage medium for reading data bits therefrom by determining the state of storage regions during relative motion between the data storage medium and the plurality of read heads, wherein each one of the plurality of read heads produces a signal representative of the state of the same one or more storage regions; and    a detector responsive to the signals for determining the data bit represented by the state of the one or more storage regions.    
   
   
       2 . The apparatus of  claim 1  wherein the plurality of read heads are positioned to successively read the same storage regions as the data storage medium moves relative to the plurality of read heads.  
   
   
       3 . The apparatus of  claim 1  wherein the detector further comprises a delay element for delaying one or more of the signals to produce time-aligned signals to which the detector is responsive.  
   
   
       4 . The apparatus of  claim 3  wherein the time-aligned signals are combined to form a composite signal for processing by the detector, and wherein the composite signal has a greater signal-to-noise ratio than the time-aligned signals.  
   
   
       5 . The apparatus of  claim 1  wherein the data storage medium is selected from among a floppy disk, a magnetic tape, a magnetic card strip, an optical storage device, a digital video disk and a compact disk read only memory.  
   
   
       6 . A method for reading data bits from a data storage medium, wherein a state of data storage medium regions represents a data bit, comprising: 
 producing a plurality of signals representative of the state of data storage medium regions;    combining the plurality of signals to determine the data bits represented by the state of the data storage medium regions.    
   
   
       7 . The method of  claim 6  further comprising time-aligning the plurality of signals.  
   
   
       8 . The method of  claim 7  wherein the step of time-aligning the plurality of signals comprises delaying one or more of the plurality of signals.  
   
   
       9 . The method of  claim 6  wherein the plurality of signals are sequentially produced.  
   
   
       10 . The method of  claim 6  wherein the step of combining further comprises introducing time delays to one or more of the plurality of signals.  
   
   
       11 . The method of  claim 6  wherein the step of producing a plurality of signals further comprises producing a plurality of signals representative of the state of data storage medium regions by a like plurality of read heads moving relative to the data storage medium.