Abstract: A preamplifier system is provided for use with a magneto-resistive (MR) sensor. Included is an alternating current (AC) coupling module connected to the MR sensor for blocking a direct current (DC) voltage associated with an input signal, and filtering low frequency noise associated with the input signal. Also provided is a gain stage module coupled to the AC coupling module. The gain stage module includes a plurality of cascode field effect transistors (FETs) configured for amplifying the input signal, while reducing intrinsic noise and increasing operational bandwidth. Coupled to the gain stage module is a control circuit for feeding back an output of the gain stage module for bias regulation and disturbance rejection.

Abstract: A preamplifier system is provided for use with a magneto-resistive (MR) sensor. Included is an alternating current (AC) coupling module connected to the MR sensor for blocking a direct current (DC) voltage associated with an input signal, and filtering low frequency noise associated with the input signal. Also provided is a gain stage module coupled to the AC coupling module. The gain stage module includes a plurality of cascode field effect transistors (FETs) configured for amplifying the input signal, while reducing intrinsic noise and increasing operational bandwidth. Coupled to the gain stage module is a control circuit for feeding back an output of the gain stage module for bias regulation and disturbance rejection.

Abstract: A servo pattern has bursts that are constructed from two frequencies in a complementary arrangement so that the servo pattern frequencies alternate in adjacent servo tracks. The servo pattern is decoded by a pair of digital notched filters so that each filter notches out readback signal data from a different one of the frequencies to form a combined PES signal produced from each respective frequency and to control movement of the head servo. The complementary arrangement of the servo bursts decreases signal gain differences between the frequencies and improves the accuracy of servo position information. The digital notched filter provides efficient processing of the readback signal and enhances easier selection of filter parameters and easier design of the servo processing circuitry. The servo pattern uses less disk surface area as compared with typical dual or quadrature servo patterns and can be recorded on the disk using fewer servo write steps.

Abstract: A demodulator for a servo control system receives a servo signal that is produced from reading a servo pattern that comprises a repeating sequence of trigonometric-compensated, phase-encoded magnetic flux transitions that extend continuously across the width of a servo track and includes a burst cosine phase detector that samples the amplitude of the servo signal at regular intervals and produces burst sample data, from which the demodulator produces a position error signal that is a substantially linear function of the servo head position relative to the servo track width. Because a plurality of amplitude samples is taken from each cycle of the servo signal, an increased signal-to-noise ratio can be obtained for the servo signal. The superior signal characteristics permit smaller and less complex demodulator elements to be used, thereby reducing the overall servo control system complexity.

Abstract: A disk head position control system having a disk head controller that moves a disk head relative to a surface of a magnetic media disk encoded with a plurality of tracks of a quadrature burst pattern includes a burst pattern that comprises an asynchronous, multi-frequency track address code having burst pattern transitions that extend across the width of a track and are arranged in staggered fashion in alternate tracks such that no transitions between adjacent tracks are aligned in the disk radial direction.