Class of fixed partial response targets in a prml sampled data detection channel

Abstract

A new class of fixed partial response targets are disclosed for use in a PRML magnetic medium read channel. The preferred embodiment exhibits an equalization response characterized by the polynomial 7+4*D−4*D,−5*D,−2*D,, where D represents the unit delay operator. This read channel target provides improved matching to the inherent magnetic channel over the known canonical class of targets (1−D)(1+D){circumflex over ( )}N, and thereby reduces equalization losses. The improved spectral matching reduces amplification of noise in the channel, thereby reducing bit-error-rates. The new class of targets also exhibits a spectral null at DC, reducing problems for offset cancellation circuitry and making the disk drive less sensitive to thermal asperities. It also exhibits a spectral depression rather than a spectral null at the Nyquist frequency, making quasi-catastrophic error sequences virtually impossible. The new class of target simplifies coding and allows RLL code ratios that approach unity, improving effective recording densities, while significantly reducing BER.