Hilbert filter for double-layer perpendicular recording media

Signal equalization using a Hilbert filter for perpendicular double-layer media in association with a geometric mean radius reader is described. A theoretical approach is presented based on reciprocity, which reveals that the equalization is equivalent to the longitudinal transformation of a magnetization vector. Thus, a readback step-like response from the perpendicular media is transformed into a single-peak pulse. At high frequencies, no gain boost takes place, in contrast to differentiators. Results of spin-stand testing with an finite-impulse response Hilbert filter are also described.