SIGNAL-PROCESSING IN RECORDING CHANNELS UTILIZING UNSHIELDED MAGNETORESISTIVE HEADS

Because unshielded magnetoresistive (UMR) heads offer excellent short wavelength sensitivity, immunity from Barkhausen noise a velocity-independent readback signal and simple construction they were chosen for use in a new high performance, multichannel tape system that operates at 80 kbpi with a 1.5 mil track width. UMR heads have two properties that present a challenge to system designers: (1) a tendency to saturate with large applied magnetic fields, and (2) a high sensitivity to long wavelength signals and noise which corresponds to an isolated pulse that extends far beyond the system’s minimum transition time, Tmin(Fig. 1). These problems were solved through a combination of write and read equalization. System performance, measured by amplitude and timing margins is excellent. This paper discusses the design of write and read equalizers and the tradeoff between them. © 1990 IEEE