Patent ID: 8139300

Claim:
An apparatus for evaluation of a magnetic recording medium, the apparatus comprising: a spin stand which rotates the magnetic recording medium; a magnetic recording/reproduction head; a mechanism to position the magnetic recording/reproduction head above the magnetic recording medium; a signal generator for generating arbitrary recording signals x n ; a recording circuit which processes the recording signals x n for recording on the magnetic recording medium using the magnetic recording/reproduction head; a reproduction circuit for providing, as reproduced signals y k , signals acquired from the magnetic recording medium using the magnetic recording/reproduction head, at a fixed sampling interval in synchronization with the recording signals x n ; a first digital filter to which the recording signals x n are input, and which outputs ideal restored signals z n when the recording signals x n are recorded; a second digital filter to which the reproduced signals y k are input, and which outputs restored signals z′ n ; comparison means for determining the difference between the output z n of the first digital filter and the output z′ n of the second digital filter; and calculating means for calculating a signal-to-noise ratio by taking an average of the absolute value of the difference determined by the comparison means as the denominator, and the amplitude of the ideal restored signals z n , as the numerator.