LAUSR

The quality of magnetic recording can be assessed from 2-D distributions of the recorded readback signal, media, and read sensor noise. The procedure for generating spatial signal and noise distributions is based on cross-track data alignment using media noise as a reference. In order to analyze signal and noise statistics, multiple data periods are processed using synchronous averaging, resulting in average readback signal and rms noise voltage maps. Using multiple signal acquisitions from the same media location allows separate measurements of media and read sensor noise distributions. Fast 2-D mapping algorithms allow high-resolution visualization of arbitrary data patterns, pole footprint imaging, and encroachment of the writer field onto adjacent tracks, providing detailed measurements of recording parameters (media jitter, dc noise saturation, signal-dependent read sensor noise, transition curvature, edge noise, and others). Recently, we have introduced a highly sensitive switching probability averaging measurement (SPAM), which allows the detection of media grain switching with unprecedented sensitivity (better than one part in 1000). This 2-D technique provides quantitative assessment of the magnetic field coming out of the write head and domain wall activity, which contributes to undesirable adjacent track erasure.