Perpendicular signal equalization and timing recovery using Hilbert transform

#1. Field of the Invention

#The present invention relates generally to perpendicular recording of data onto magnetic recording disks.

#2. Description of the Related Art

#FIG. 1 is a block diagram of a first embodiment of the present system;

#FIG. 1A shows an IF quantizer for the (1,7) code for translating the magnetic angle variations into zero run length estimates;

#FIG. 2 is a block diagram of a second embodiment of the present system;

#Referring initially to FIG. 1, a magnetic recording readback system is shown, generally designated 10, for processing signals represented by magnetic transitions on a magnetic storage or recording medium 12. It is to be understood that the medium 12 can be a magnetic disk of a hard disk drive, although other recording media, such as magnetic tape, floppy diskette, and so on can be used.

#In the architecture shown in FIG. 1, the signal (designated S(t)) from the medium 12 is sent to an envelope calculator 14 which, in accordance with the logic of FIG. 7 below, combines the signal with a transform thereof (designated S(t)) to render an envelope magnitude signal. The Hilbert transform is generated by a main Hilbert transform 16 as shown, which also receives the perpendicular signal from the disk. A preferred implementation of the main Hilbert transform 16 is described further below in reference to FIG. 4.

#In effect, the output of the main Hilbert transform 16 represents the readback that would be expected from a parallel (or longitudinal)-recorded disk, and it is sent to a conventional read channel 18. While all conventional read channels are contemplated herein, the exemplary read channel 18 includes in series, in accordance with principles known in the art, a variable gain amplifier (VGA) 20, a continuous time filter (CTF) 21, an analog to digital converter (ADC) 22 and a digital finite impulse response (FIR) equalizer 23. Thus, the Hilbert transform 16 cooperates with the equalizer to transform the perpendicular signals to longitudinal signals. From the DFIR 23 the signal is sent to a VA detector 24 which outputs the detected bits from the disk. The VA detector 24 and DFIR 23 also send their outputs to digital loops 25 which, in accordance with longitudinal read channel principles known in the art, output a signal to the VGA 20 to provide timing and amplitude control. Moreover, the loops 25 output a signal representing estimated transition locations to a phase and frequency control module 26, which in turn outputs a control signal to the ADC 22.