Self-synchronization in a magnetic recording channel utilizing time-domain equalization

In a disc drive of the type having a rotatable magnetic storage disc and an actuator adjacent the disc, the actuator including a head for the selective magnetization of the disc to store data on the disc and for the generation of a readback signal having peaks indicative of magnetic transitions in the data stored on the disc, an improved recording channel for the reconstruction of the stored data from the readback signal comprising:

• a time-domain equalizer, responsive to the readback signal, for filtering the readback signal to an approximation of a waveform of a selected class of partial response signaling, the time-domain equalizer including:
• serially-connected analog filter sections having associated tap locations;
• analog multipliers, connected to the tap locations, for multiplying tap signals from the tap locations by tap weight signals to generate product signals;
• an analog summer, connected to the multipliers, for generating an equalized output signal from the product signals;
• a sampler circuit, connected to the analog summer, for sampling the equalized output signal;
• a voltage controlled oscillator for generating a vco clock signal;
• a detector circuit, responsive to a selected tap signal from a selected tap location, for detecting the timing of a peak in the readback signal indicative of a magnetic transition on the disc, the detector circuit comprising:
• a differentiator for differentiating the selected tap signal from the selected tap location to generate a differentiated tap signal;
• a gated peak detector, comprising:
• a non-zero threshold comparator responsive to the selected tap signal;
• a zero threshold comparator responsive to the differentiated tap signal;
• an AND gate responsive to the non-zero threshold comparator and the zero threshold comparator to generate a gated signal indicative of the presence and timing of the peak in the readback signal;
• and
• a phase data comparator, responsive to the gated peak detector and the voltage controlled oscillator, for generating a timing error signal from the difference between the vco clock signal and the gated signal, wherein the timing error signal adjusts the frequency of the vco clock signal generated by the voltage controlled oscillator;
• a timing delay circuit, responsive to the vco clock signal, for generating a clock signal used by the sampler circuit to time the sampling of the equalized output signal, the timing delay circuit including a programmable delay so that the clock signal generated by the delay circuit comprises the vco clock signal adjusted in time by an amount equal to the programmable delay;
• and
• a timing delay calibration circuit, connected to the timing delay circuit and the sampler circuit, for adjusting the programmable delay used by the timing delay circuit in response to samples provided by the sampler circuit.

In a magnetic recording channel wherein data is recovered from a magnetic medium through the detection of flux transitions in the magnetization of the medium, a method for self-synchronizing the rate of data recovery by the magnetic recording channel, comprising the steps of:

• generating an equalized output signal by filtering a readback signal to an approximation of a selected waveform, the readback signal indicative of the magnetization of the medium, comprising the steps of:
• sequentially filtering the readback signal in a plurality of serially connected analog filter sections having associated tap locations, including a main tap location;
• multiplying tap signals from the tap locations by tap weight signals to generate product signals;
• summing the product signals to obtain the equalized output signal;
• differentiating the main tap signal from the main tap location to generate a differentiated main tap signal;
• generating a gated signal from the main tap signal and the differentiated main tap signal, the gated signal having a rising edge corresponding to a peak in the readback signal indicative of the presence and the timing of a magnetic transition;
• generating a vco clock signal having a controllably selectable frequency;
• comparing the vco clock signal to the gated signal to generate a timing error signal;
• adjusting the frequency of the vco clock signal using the timing error signal;
• and
• delaying the vco clock signal by a programmable amount of delay to generate a channel clock used by the magnetic recording channel for the recovery of the data stored on the medium from the equalized output signal.

In a disc drive of the type having a rotatable magnetic storage disc and an actuator adjacent the disc, the actuator including a head for the selective magnetization of the disc to store data on the disc and for the generation of a readback signal having peaks indicative of magnetic transitions in the data stored on the disc, the disc drive further including a magnetic recording channel for reconstructing the stored data from the readback signal, a method for self-synchronizing the rate of data recovery by the recording channel, comprising:

• generating an equalized output signal by filtering the readback signal to an approximation of a selected waveform, comprising the steps of:
• sequentially filtering the readback signal in a plurality of serially connected analog filter sections having associated tap locations, including a main tap location;
• multiplying tap signals from the tap locations by tap weight signals to generate product signals;
• summing the product signals to obtain the equalized output signal;
• differentiating the main tap signal from the main tap location to generate a differentiated main tap signal;
• generating a gated signal from the main tap signal and the differentiated main tap signal, the gated signal having a rising edge corresponding to a peak in the readback signal indicative of the presence and the timing of a magnetic transition;
• generating a vco clock signal having a controllably selectable frequency;
• comparing the vco clock signal to the gated signal to generate a timing error signal;
• adjusting the frequency of the vco clock signal using the timing error signal;
• and
• delaying the vco clock signal by a programmable amount of delay to generate a channel clock used by the magnetic recording channel for the recovery of the data stored on the disc from the equalized output signal.