Harmonic sensor phase error detection for data storage devices

Abstract

Example systems, data storage devices, and methods for using a harmonic sensor in the read channel of a data storage device to determine phase error are described. The data storage device includes a storage medium with data tracks and a head that can be positioned for reading and writing those tracks. A tone pattern may be written to a data track and a read signal from the tone pattern may subsequently be processed through the harmonic sensor to acquire amplitude data corresponding differences between a target frequency of the tone pattern and a read frequency from the read signal. The amplitude data may be processed to determine phase error values that correspond to an operating condition during writing, such as mode hops and/or down track thermal gradients related to operation of a laser during heat assisted magnetic recording.