Patent ID: 7872821

Claim:
A storage device, the storage device comprising: a storage medium, wherein the storage medium includes a periodic data pattern, and wherein the periodic data pattern repeats at a data frequency; an offset frequency; a read/write head assembly disposed in relation to the storage medium, wherein the read/write head assembly senses the periodic data pattern and provides a sensed periodic data pattern; and a harmonic fly-height change detection circuit, wherein the harmonic fly-height change detection circuit samples the sensed periodic data pattern at an aggregate frequency to yield a first set of samples and a second set of samples, wherein the aggregate frequency is the data frequency adjusted by the offset frequency, and wherein the harmonic fly-height change detection circuit calculates a first magnitude of the first set of samples and a second magnitude of the second set of samples; and wherein the harmonic fly-height change detection circuit is operable to detect a change in a distance between the storage medium and the read/write head assembly based at least in part on a combination of the first magnitude of the first set of samples and the second magnitude of the second set of samples.