Measurements of linearity in high density magnetic recording

Wideband signal and noise measurements on various magnetic media are used to explore linear superposition of a magnetic recording channel. Various sources of experimental error are identified that limit the accuracy of the measurement of the isolated transition response (ITR). Quantitative expressions are derived to correct the signal response spectrum calculated from time-averaged ITRs; the errors corrected are caused by jitter due to wideband system noise, modulation noise, and quantization noise. Linear superposition of the tested recording channel is experimentally verified to be valid up to more than 160 KFCI. Since linear superposition implies an ITR independent of bit density, it is concluded that record demagnetization is negligible for high-density, in-contact recording with a 0.2-μm Sendust-tipped head