Data pattern for fly height measurement

摘要

A hard disk drive that includes a disk and a head that is separated from the disk by a flying height. The disk drive also includes a circuit that determines the flying height from an equation that uses a third harmonic of a read signal. The read signal includes a data pattern that is a product of a first data pattern and a second data pattern. The resultant data pattern provides a third harmonic with a relatively high magnitude and improved signal to noise ratio.