Creation of Data Pattern for High Accuracy Flying Height Measurement

A common technique for measuring flying height is using the ratio of the 1st and the 3rd harmonic of a periodic data pattern. Since the 3rd harmonic is typically smaller than the 1st, and the recording channel usually rolls off at higher harmonics, the magnitude of the 3rd harmonic dominates the signal to noise ratio of the measured flying height. Therefore it is desirable to create a data pattern that has a large 3rd harmonic component for flying height measurement. This paper describes a method to create data patterns with a high frequency component larger than the 1st harmonic. The method multiplies a high frequency signal to a basic periodic signal to create a high frequency component and a low frequency component. The high frequency signal may be the 3rd harmonic and can be larger than the low frequency one. In addition, newly created data pattern was applied to real hard disk drive, and the accuracy of measured flying height was demonstrated in comparison with measured flying height based on conventional data pattern.