(1+D)n partial response channels for UMR heads

Most partial response channels described in the magnetic recording literature are characterized by the (1-D)(1+D)ⁿ pulse response polynomial, where n=1 for PR4 and 2 for EPR4. Partial response channels with (1+D)ⁿ pulse response polynomials, which include partial response classes 1 and 2 (PR1(1+D) and PR2(1+D)²), have received scant attention because magnetic recording systems lack the DC component implicit in these polynomials. A new channel developed for the unshielded magnetoresistive (UMR) head that closely approximates a (1+ D)ⁿ channel at all but the very lowest frequencies and works well when used with DC-free modulation codes is discussed. This channel is an excellent match to the UMR head response, which has greater long wavelength response than the more familiar inductive and shielded MR heads