Bit cell aspect ratio: An SNR and detection perspective

Future gains in areal density may require using bit cells which have smaller width-to-length aspect ratios than have been customary in magnetic recording (15 to 20:1). Common thinking is that such squarer bits have a media signal-to-noise advantage. This conclusion depends on the SNR formulation used, e.g, raw voltage SNR vs. a timing window/jitter SNR. Despite this conundrum, it is found that (PR4) equalization transforms the voltage signal and noise in such a way that the equalized voltage SNR, like the raw timing window/jitter, favors squarer bits. The presence of significant electronic noise weakens this conclusion.